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Evolving climates and mammal faunas in Cenozoic South America
Abstract
A multivariate analysis of the current South American Land-Mammal Ages is used to reanalyse the recognized “faunistic (mammal) units” or chronofaunae that appear related to radical environmental and climatic changes, which we characterize as Faunistic Cycles and Subcycles. The compositional changes recorded in the successive Faunistic Cycles reflect regional environmental and climatic variations, thus patterns of climatic change. Basically we used cheek teeth of ungulates—natives and immigrants—as an indicator of dietary preference. We then try to infer the structure of successive fossil ungulate communities to deduce the structure of their associated vegetation, and thus the prevailing climatic conditions. We also used other native mammals that followed similar dental modifications, e.g., some rodents and some marsupials, and various types of biological and/or geological evidence. These include climate-sensitive or ecologically specific animals or plants, changes of regional distribution and lithological features of the mammal-bearing formations, diastrophic events, changes in global marine temperatures, and sea-level changes, to contrast those climatic and environmental inferences.
We conclude that: (1) From the oldest to the youngest cycles the ungulates changed from browser sylvan types to predominantly open country and grazer types as warm, humid sylvan environments became drier and more temperate. (2) The earliest mammal communities (Paleocene-Eocene), excluding the peculiar Cochabambian Cycle, show a higher diversity but are composed of taxa with less extreme morphological differences. Even mammals placed in different orders were not nearly as dissimilar as their later counterparts. This relationship gradually became reversed within the later communities, i.e., lower diversity but taxa with more extreme morphological differences; that is, mammals placed in separate orders became more divergent. (3) According to the record of mammals as well as other climate-sensitive organisms, warm and relatively humid forested environments had a wider latitudinal range, stretching at the very least to the northern part of the Antarctic Peninsula. (4) With some regional range fluctuations, Palcogene and Early Miocene tropical to subtropical environments remained very well represented as far as the southern tip of the continent. (5) The Middle Miocene mammals (beginning of the Panaraucanian Faunistic Cycle) indicate that favorable environments were shifted to northern Patagonia and that many climate-sensitive mammals (including platyrrhine monkeys) disappeared from Patagonia, in correlation with the waning or extinction of many taxa related to subtropical woodlands. (6) Mammals of the Panaraucanian Cycle and the Pampian Subcycle clearly indicate that this was the time of the most extensive open-country environments, progressively ranging from wetter subtropical savannas to cold-temperate steppe-like habitats. Most of the mammals of this time were savanna-adapted or steppe-adapted elements. (7) Mammals representing the Postpampian Subcycle attest to the wide swings and cyclicity of the Cenozoic climates. (8) According to the Brazilian mammal records, as well as other biological evidence from the isthmian region, the rainy forested areas characterizing those regions evolved quite recently, by the latest Pleistocene to Recent times.
... The advent of the Rosellichnus ichnoassemblage reveals a change in the invertebrate fauna pointing in the direction of the extant one, which is also accompanied by other elements of the ecosystems. For instance, Colloncuran mammals show a strong reduction of subtropical taxa from older Miocene faunas (Pascual and Ortiz Jaureguizar, 1990). Patagonian floristic assemblages also experienced an important turnover since the middle Miocene, through the gradual expansion of shrubby and herbaceous xerophytic taxa, reduction of forests and extinction of megathermal elements (Barreda and Palazzesi, 2007). ...
... At Paso del Sapo locality, the mammal fauna from the Collón Curá Formation includes Colloncuran and Mayoan elements, but that from El Petiso includes post-Colloncuran (Laventan) elements (Bucher et al., 2021). During the Colloncuran time, most mammals suggesting subtropical woodlands became wholly extinct, rare or absent, while high-crowned taxa were widely prevalent (Pascual and Ortiz Jaureguizar, 1990;Bellosi et al., 2021). On balance, this was related to steppe-like palaeoenvironments (Pascual and Ortiz Jaureguizar, 1990). ...
... During the Colloncuran time, most mammals suggesting subtropical woodlands became wholly extinct, rare or absent, while high-crowned taxa were widely prevalent (Pascual and Ortiz Jaureguizar, 1990;Bellosi et al., 2021). On balance, this was related to steppe-like palaeoenvironments (Pascual and Ortiz Jaureguizar, 1990). According to Iglesias et al. (2011), the proportion of xeric spinose elements in extra-Andean North Patagonia increased substantially since 13 Ma (middle Miocene), defining the Protoespinal/Steppe palaeophytogeographical province . ...
The ichnofacies and palaeosols from the La Pava and Collón Curá formations were studied to shed light on the evolution of terrestrial ecosystems from Patagonia (Argentina) during the Middle Miocene Climate Transition. At Paso del Sapo, Cerrito Terciario and El Petiso localities (Chubut province), the La Pava Formation included Coprinisphaera ispp., Rosellichnus patagonicus, Rebuffoichnus casamiquelai, Feoichnus challa and burrows of spiders and earthworms, representing a case of the Rosellichnus ichnoassemblage of the Coprinisphaera Ichnofacies. Some of the components of this ichnoassemblage, scarce or absent in Cenozoic formations older than La Pava, are present in extant Patagonian habitats, pointing in the direction of extant invertebrate fauna. At El Petiso locality, the Collón Curá Formation included Celliforma ispp., Rosellichnus patagonicus, Fictovichnus ispp., Teisseirei barattinia and Teisseirei paladinco isp. nov., representing a case of the Celliforma Ichnofacies. The La Pava Formation comprises brownish, argillic, granular and strongly-developed palaeosols (Mollisols and Alfisols) formed in mildly stable to long-lasting landscapes, whereas the Collón Curá Formation comprises calcic, tuffaceous, paler and weakly-developed palaeosols (Andisols, Aridisols) formed in unsteady and ashy environments. The ichnofacies and palaeosols from the La Pava Formation indicate wooded grasslands developed in seasonal, subhumid and temperate-warm conditions, whereas those from the Collón Curá Formation indicate a habitat with reduced plant cover similar to semiarid and temperate-warm dry woodlands or bushlands. This shift towards more arid conditions in Patagonian landscapes would have been coeval with climatic changes corresponding to the Middle Miocene Climate Transition, a lapse of global temperature decrease associated with extensive drying.
... Environmental changes during the Tertiary significantly altered the taxonomic and ecological composition of mammalian communities, operating through cladogenetic processes, extinction, and immigration from other areas. The changes that occurred during the Quaternary are responsible for chorological variations, expanding or contracting the distribution areas of species, communities, and biomes [59][60][61]. The successive retreat and advance of the glaciers produced, in non-engulfed areas such as the Pampeana Region, an alternation of arid (savanna, steppes) and humid (subtropical forests) biomes. ...
... The SALMA arrangement comprises unique taxon associations that are inferred to have existed during a restricted time interval (Table 1). These Ages were established using knowledge of the faunas' evolutionary grade, in the same way that Ameghino did, by noting the times of first and last taxa appearances in the fossil record and other related changes in faunal assemblages over time [59]. The LMA are stratigraphic units that, for the moment, have not been formally recognized by the stratigraphic code of nomenclature of Argentina. ...
... However, as a classifying scheme, they have been very useful in evolutionary and biogeographic mammal studies [84,85]. Pascual et al. [59], among others, have underlined its usefulness in establishing intra-and intercontinental correlations of Cenozoic time. ...
The Pampean Region contains sedimentary sequences with abundant mammal fossil records, which constitute the chronological outline of the Plio–Pleistocene of South America. These classic localities have been used for more than a century to correlate with other South American regions. Throughout this time, a series of misinterpretations have appeared. To understand the stratigraphic significance of these localities and the geochronological situation of each unit referring to the Pleistocene, a critical historical study of the antecedents was carried out, evaluating the state of each unit. The biostratigraphic studies of the Pampean Region’s mammalian faunas improved the understanding of biogeographic changes taking into account the environmental fluctuations of the Pleistocene.
... Southern South America has been long considered the region where grasslands and grazer mammals may have appeared (Patterson and Pascual, 1972;Stebbins, 1981;Retallack, 2001b;Pascual and Ortíz, 1990;Woodborne et al., 2014), a proposal that has been more recently supported by different evidence coming from the Eocene Bellosi and González, 2010, Sánchez et al., 2010a, 2010bBellosi and Krause, 2014;Zucol et al., 2010Zucol et al., , 2018. Nevertheless, other authors proposed that this process occurred after Early Miocene Azevedo et al., 2020), or after Pliocene (Palazzesi and Barreda, 2012). ...
... Assuming that the amount of brood balls in a single bed does not represent a unique breeding season, but the sum of several ones, and considering that paleosols of Upper Puesto Almendra Member involve more time than those of the Lower Puesto Almendra Member, the original Coprinisphaera concentration in the first dung beetle burst (middle Eocene) should have been much higher yet. The enlargement of this trace fossil (Fig. 5B) in the late Oligocene matches with the appearance of huge mammals of the Deseadan SALMA (Pascual and Ortíz, 1990;Sanchez et al., 2010a). A subsequent waning in the community of dung beetles is observed through the record of Coprinisphaera in the uppermost section of the Sarmiento Formation and its noteworthy absence in the Santa Cruz Formation . ...
... However, different interpretations may arise. For instance, the first proposal of Eocene subhumid, open herbaceous vegetation based on detailed phytolith study (Zucol et al., 2010) was later refuted and replaced by humid closed forests , a hypothesis that challenged the geological and paleontological evidence (Pascual and Ortíz, 1990;Bellosi and González, 2010). This was shortly after rectified into scrubs-open forests , and currently most specialists agree with the paleoecological vision of open habitats. ...
Timing and ecological steps of the rise and expansion of grasslands differ not only geographically but also according to the type of available information. Patagonia (Argentina) was largely considered the region where grasslands and grazers early evolved in the Eocene, mostly based on functional morphology of mammals. However, recent paleobotanical studies question this traditional view and maintain that this occurred after early Miocene. To tackle this discrepancy, we conduct a multidisciplinary and integrative approach using diverse lines of evidence obtained from middle Eocene - middle Miocene tuffaceous deposits of central and northern Patagonia. Gathered data correspond to sedimentary facies, paleosols, insect trace fossils, opal phytoliths and fossil mammals (tooth morphology, body size). Long-lasting and frequent volcanic ashfalls caused permanent disturbances in physical scenarios, biotic systems and grassy habitats; just like herbivory of mammals through coevolutionary grass-grazer mechanisms. The results indicate that soils, vegetation, insects and mammal herbivores begun synchronously to record diverse traits related to grasslands showing mosaic vegetation since middle Eocene (∼44 Ma). These traits include mollic paleosols, abundant and persistent dung beetle trace fossils (Coprinisphaera ichnofacies), phytolith assemblages attributable to savannas and medium to large-size hypsodont mammals. We also track the evolutionary history after the reduction of closed forests, recognizing alternating subhumid savannas with riparian forests, where the relative frequency between grasses, palms, trees and shrubs fluctuated in time and space; and desert vegetation (shrublands) dominated by palms and shrubs during dryer periods. The advent and expansion of grasslands can be linked to the cooling and drying period subsequent to the Early Eocene Climate Optimum.
... Moreover, the SCF contains the best preserved high-latitude continental biotic record in the Southern Hemisphere providing further insights into mid-Miocene temperature and precipitation. It is well known that floras and faunas dependent on warm, wet conditions expanded to higher latitudes in South America at that time (Frenguelli, 1953;Ortiz-Jaureguizar and Cladera, 2006;Pascual and Odreman Rivas, 1971;Pascual and Ortiz-Jaureguizar, 1990). The analysis of Hinojosa (2005) of early and middle Miocene floras at 33-34 • S latitude between 21 and 13 Ma, suggests an increase in mean annual temperatures (MATs) from the late Oligocene-early Miocene from 16-17 • C to MATs exceeding 22 • C. Likewise, at the beginning of the Miocene, the floras indicate an even more abrupt rise in rainfall, which culminated in values exceeding 1000 mm. ...
... It is important to separate two questions related to the mammalian fossil record of the SCF: what does it tell us about the paleoenvironment and what does it indicate about structure of the biotic community (p.333 in Kay et al., 2012). In other words, estimating MAP or MAT on one hand and identifying the biotic environment on the other hand are distinct but There is general agreement in the older literature that temperate conditions with sufficient rainfall to support a mixture of forested and open environments prevailed in the time interval represented by the SCF (Pascual and Ortiz-Jaureguizar, 1990). Tauber (1997a) divided the coastal exposures of SFC south of Río Coyle into two members and evaluated the mammal faunas of each separately. ...
... Comparing faunas from the two levels using the cenogram approach of Legendre (1986), Croft (2001) found the two levels to be very similar and concluded that no obvious environmental changes had occurred. Noting, as had others, that the fauna in both members of the coastal SCF includes a combination of arboreal (the primate Homunculus) and savanna-adapted mammals, he suggested that the region was moister and less open (i.e., having a more continuous canopy in places) than proposed by Pascual and Ortiz-Jaureguizar (1990). Whereas Tauber (1997b) suggested that the SCF climate had become less humid and more open during this interval, Croft's interpretation was that there might even have been slightly more rainfall in the upper levels. ...
The continental early-middle Miocene Santa Cruz Formation (SCF) and its fossils in Austral Patagonia represent the best record of South American mammalian faunas prior to the Great American Biotic Interchange (GABI) and is of particular interest because it is the best preserved high-latitude continental biotic record in the Southern Hemisphere spanning the mid-Miocene Climatic Optimum. Through intensive fieldwork we recovered numerous fossil vertebrates, mostly mammals, from the SCF along the Río Santa Cruz (RSC), the type area for the formation and its fauna. We examine whether the SCF fauna differed among three distinct temporal intervals of the SCF spanning, from the oldest to youngest, the Atlantic coastal suite of localities Fossil Levels (FL) 1–7, at about 17.4 Ma, through localities in the RSC Barrancas Blancas (BB), between ∼17.2 and ∼16.3 Ma, and Segundas Barrancas Blancas (SBB), between ∼16.5 and ∼15.6 Ma. With the objective of reconstructing paleoenvironmental and community structure of these RSC faunas, we compared them with 55 extant lowland mammalian localities across South America from 8° N to ∼55° S latitude representing a wide range of seasonality and annual rainfall and temperature, as well as canopy height and net primary productivity, sampling communities ranging from tropical rainforest to semi-arid steppe. Extant nonvolant mammalian genera at each locality were assigned a body size interval and niche parameters reflecting diet and substrate use, from behavioral data in the literature. Extinct genera were assigned similar niche metrics on the basis of their morphology. From the generic niche parameters, we compiled indices and ratios that express vectors of the community structure of each fauna, including the total number of genera, the pervasiveness of arboreality, frugivory, and browsing, and the relative richness of predators to their prey. The community structure variables were used to model community structure of the fossil localities based on uniformitarian principles. The fossil sample includes 44 genera of mammals from FL 1–7, 38 genera from BB, and 44 genera from SBB. The Simpson Coefficients of faunal similarity among the fossil localities are no greater than expected on the basis of the geographic distances among them, and do not suggest any apparent climatic differences. Based on the models we obtained no significant differences in MAP (Mean Annual Precipitation) for FL 1–7, BB and SBB, with mean estimates of 1635 mm, 1451 mm, and 1504 mm, with the confidence intervals for the estimates overlapping widely. MAT (Mean Annual Temperature) estimates are between ∼21 °C and ∼22 °C for FL 1–7 and SBB, possibly lower at 16 °C for BB, but with a wide and overlapping range of estimates. Temperature seasonality is modest (3 °C to 4 °C) and similar for all localities. Canopy heights exceed 20 m for all sites. Despite these geographic and inferred climatic similarities, the presence of certain key taxa (e.g., the caviomorph rodent Prolagostomus and the typothere Pachyrukhos) together with an increased overall abundance and richness of rodents with ever-growing cheek teeth suggests a trend to aridification in the upper part of the SCF at SBB compared with FL 1–7 and BB. Taken together, we propose that the SCF paleoenvironment consisted largely of semi-deciduous forests ranging into savannas with gallery-forest components. This range of habitats occurs today where the mesic inland Atlantic forests of Southern Brazil, northeastern Argentina and eastern Paraguay give way northwestward into the more xeric Paraguayan Gran Chaco. This interpretations are in general agreement with the other sources of evidence from sedimentology, paleosols, isotopes, paleobotany and other faunal elements. We highlight the value of focusing paleoenvironmental and paleocological studies of the SFC on stratigraphically and geographically controlled samples instead of on the entire temporal and geographic distribution of the formation based on historical collections with limited provenance. The Santacrucian can be considered a model to the study of South American faunas after the arrival of hystricomorph rodents and anthropoid primates but before GABI.
... This event had a significant local effect on rainfall beginning in the mid-Miocene, enabling the formation of mountain glaciers and a combination of global cooling and regional aridity in the area, which is testified by the paleoflora and marine environmental as well (Palazzesi et al. 2003;Rabassa 2008;Aragón et al. 2011;Brea et al. 2012;Kay et al. 2012). Furthermore, this drastic geological change caused the displacement of the continental sedimentary basins northward from the middle Miocene, with no continental Tertiary mammal-bearing formations extending to the southerly Patagonian latitudes (Pascual and Ortíz-Jaureguizar 1990). ...
... The middle Miocene mammal record from Patagonia provides a clear view of sharp paleoenvironmental changes, indicating that subtropical to tropical environments shifted from southern to northern Patagonia (~30S) (Pascual and Ortíz-Jaureguizar 1990). Humid subtropical forest environments, which had persisted to the southern end of South America through the Paleogene and early Miocene, abruptly shifted to colder, drier grassland environments in the middle Miocene. ...
... These cool events forced changes in the plant cover, with large latitudinal displacements of the major ecosystems during glaciations, closely followed by a significant terrestrial faunal replacement with northward expansion of Patagonian faunas (Rabassa 2008). The Santa Cruz Formation (Patagonia, Argentina) constitutes one of the best testimonies that suggests the climatic conditions shifted from warm and humid in the early Miocene to cooler and more arid conditions in the middle Miocene (Kay et al. 2012), where the notoungulates were the most sensitive environmental indicators among the South American extinct ungulates (Pascual and Ortíz-Jaureguizar 1990). Among them, the typothere Protypotherium became an interesting proxy to evaluate association between environmental changes and biotic attributes due to its long biochron through the Miocene and the relatively high diversity. ...
Protypotherium (Mammalia, Notoungulata, lnteratheriinae) is a well-known and very diverse genus of extinct native ungulates of South America, widely distributed from southern to middle latitudes of Argentina, Chile, and Bolivia. This genus exhibits distinctive species throughout the Miocene to the beginning of the Pliocene that display an interesting size pattern. The large sample of specimens studied during several years of research allows us to analyze the shape and size of upper and lower molars for nine species of Protypotherium, in order to test the hypothesis of reduction of size ranges preserving a general tooth morphology as a response to climate deterioration, documented in South America by a marked reduction of temperature that occurred during Miocene times. Elliptic Fourier analyses were used to capture the shape of the occlusal morphology and the centroid size was also retained for subsequent analyses. Our results demonstrate that: 1) a similar morphological tooth pattern is observed among all species; 2) tooth shape variation is not associated with a change in size; and 3) there is a tendency to increase the size and decrease the number of species. This striking pattern could be correlated with a global trend to lower temperatures, which indicates a deterioration of paleoenvironmental conditions. A conservative tooth pattern, together with an increase of size and a reduction in number of species were the main evolutionary and ecological tendencies accounted in Protypotherium from the early to late Miocene-beginning of the Pliocene, which were accompanied by a latitudinal displacement from Patagonia to northern areas at the end of the Miocene.
... For the temporal framework (see Fig. 2.1), the South American Land Mammals Ages (SALMAs) system (e.g., Marshall et al. 1983;Pascual and Ortiz Jaureguizar 1990;Flynn and Swisher 1995) is used for the Oligocene-Middle Miocene time Rasia et al. (2021) and Croft et al. (2021)) showing changes in hypsodonty and body mass. Isotopic curve modified from Zachos et al. (2008). ...
... .1). The Fifth DE, during the Late Miocene, was probably related to a progressive cooling and to the expansion of more arid and open environments in southern South America(Pascual and Ortiz Jaureguizar 1990), a time interval known as "Edad de las Planicies Australes" (Age of the Southern Plains; seeOrtiz Jaureguizar 1998;Ortiz Jaureguizar and Cladera 2006). ...
Pan-Chinchillidae is a clade of caviomorph rodents that includes extant chinchillas (Chinchilla spp.) and mountain vizcachas (Lagidium spp.) within Chinchillinae, and the plains vizcacha (Lagostomus maximus) as the sole living member of Lagostominae. Despite its relatively low diversity in recent times, the past diversity of the group was higher (8 extinct genera and nearly 20 extinct species) and with an ancient fossil record starting in the Early Oligocene. Stem chinchillids were recorded since the Early Oligocene to the Early Miocene in Argentina, Bolivia, and Chile and were represented by the extinct genera †Eoviscaccia, †Garridomys, †Loncolicu, †Saremmys, and †Incamys. Crown Chinchillidae are recorded from the Early to Middle Miocene, including both extant subfamilies, Chinchillinae (†Miochinchilla) and Lagostominae (†Prolagostomus and †Pliolagostomus). Among extant genera, Lagostomus has been recorded since the late Middle to Late Miocene, while Lagidium has been recorded since the Pleistocene and Chinchilla since the Holocene. Five main Diversification Events (DE) can be recognized in the evolutionary history of pan-Chinchillidae. The First DE (late Eocene/Early Oligocene) gave origin to the group. The Second DE (late Early to early Late Oligocene) and Third DE (earliest Early Miocene) are related to the diversification of stem chinchillids. The Fourth DE (late Early Miocene) represents the rising of crown Chinchillidae. First to Fourth DEs match with peaks of maximum cooling, followed by progressive warming intervals. The Fifth DE (Late Miocene) is marked by the origin of the extant genus Lagostomus and was probably related to a progressive cooling and the expansion of more arid and open environments in southern South America. The appearance of euhypsodonty in crown chinchillids during the Fourth DE, contrasting with previous protohypsodont stem chinchillids, may be related to the increase of volcanic activity in nearly all the Andean chain since the Late Oligocene. The maximum estimated body mass (MEBM) for the pan-chinchillids is quite stable until the Late Miocene. The MEBM of pan-chinchillids from the Early Oligocene to the Late Miocene was between 300 and 1300 g. After the Late Miocene, the MEBM increased notably, reaching more than 5000 g in the Pliocene, 8000 g in the Late Pleistocene-Holocene, and ~9000 g with the extant plains vizcacha, Lagostomus maximus. The increase of the MEBM for the pan-Chinchillidae in the latest Late Miocene coincides with the global expansion of grasslands and the Age of the Southern Plains.
... These strata are unconformably followed by upward-coarsening alluvial synorogenic beds (Santa Cruz Fm., and correlatives; Cuitiño et al., 2016;2012), interpreted as the main phase of Cenozoic deformation and surface uplift in the Patagonian Cordillera (Blisniuk et al., 2005;Lagabrielle et al., 2007). The southern Patagonia foreland would have been characterized by a subtropical humid climate in the Paleogene to middle Miocene, and a semiarid to arid climate since then (Blisniuk et al., 2005;Flynn and Swisher, 1995;Pascual and Jaureguizar, 1990). In consistency with this, and based on carbon and oxygen isotope analyses of pedogenic carbonate nodules from this unit, Blisniuk et al. (2005) interpreted an increase in aridity across the eastern foreland, and attributed it to the formation of an orographic rain shadow by the middle Miocene J o u r n a l P r e -p r o o f (ca. ...
... For the first 3.5 Myr (i.e., from 20 to 16.5 Ma), the model ran at a homogeneous rate of 1500 mm/yr across the domain in order to simulate humid climates (cf. Blisniuk et al., 2005;Flynn and Swisher, 1995;Pascual and Jaureguizar, 1990). (Fig. 2). ...
The subduction of seismic oceanic ridges often results in the formation of slab windows, which can affect not only the heat flow and retroarc volcanism, but also the exhumation and topographic evolution of the upper plate. An active and world-class example of a slab window is southern Patagonia, in southernmost South America, which is related to the subduction of the seismic oceanic South Chile Ridge between the middle–late Miocene and the Present day. How the subduction of the ridge and formation of the slab window have influenced the evolution of the Patagonian landscape, exhumation and topography is still under debate. Some works have proposed orogenic deformation mostly affecting the Pacific margin and hinterland areas, or an inherited early Miocene tectonic relief generated before the slab window formation. Others have preferred epeirogenesis hypotheses, such as dynamic uplift or isostatic rebound as a result of lithospheric thinning associated with asthenospheric or lithospheric mantle changes. In this work, we analyze the landscape evolution at medium (orogen-scale) and long wavelengths (embracing the whole of southern Patagonia, from coast to coast) using FastScape a landscape numerical model. This program was coupled with an optimization scheme (the Neighborhood Algorithm) suitable for nonlinear inverse problems. The “goodness” (fit to data) of our landscape evolution models was evaluated using: i) cooling ages, and ii) maximum elevations, in order to provide constraints on the uplift rates, erosion efficiency and effective elastic thickness. We then used the best values to compare two forward models representing medium- versus long-wavelength processes. Our results indicate that long-wavelength uplift geometry (including dynamic uplift and/or lithospheric rebound from thinning) involving areas from the Andes to the Atlantic coast was required from 12 Myr to the Present day in order to reproduce not only the youngest cooling ages but also Present-day topography.
... El descubrimiento y la sucesiva descripción de la asociación de mamíferos paleocenos de la Formación Santa Lucía en la localidad boliviana de Tiupampa (véase Muizon et al. 2019 y bibliografía allí citada), llevó a algunos autores a pensar que, a partir del carácter generalizado de los mamíferos Theria allí presentes, se trataba de una asociación referible al Cretácico Superior (Marshall et al. 1981) o al Paleoceno más temprano (e.g., Muizon et al. 2019 y bibliografía allí citada). Una posición intermedia fue argumentada por Pascual y Ortiz Jaureguizar (1991), quienes sostuvieron la pro-bable contemporaneidad de ambas faunas, al tiempo que señalaron que las diferencias composicionales entre ambas ( Fig. 9) podían obedecer a un fuerte sesgo biogeográfico (véase también Ortiz Jaureguizar 1996, Pascual y Ortiz Jaureguizar 1990, Pascual et al. 1996, Morrone 2002, Pascual 2006, Ortiz Jaureguizar y Pascual 2011, Goin et al. 2012. Lamentablemente, hasta el momento la edad de la asociación de Tiupampa no está respaldada por dataciones absolutas sino por correlaciones magnetoestratigráficas . ...
... Esto indica la existencia de una radiación rápida y temprana, al menos entre los mamíferos Theria, en la parte austral de América del Sur (y, probablemente, la Antártida), radiación que involucró a la totalidad de una biota claramente diferente a la de las regiones intertropicales de este continente. Interpretaciones similares han sido dadas repetidamente en las últimas décadas (e.g., Ortiz Jaureguizar 1996, Pascual 2006, Pascual y Ortiz Jaureguizar 1990, Morrone 2002, Goin et al. 2012. ...
The terrestrial mammal diversity recovered from levels of Banco Negro Inferior (Lower Black Bank) at Punta Peligro and surrounding areas, in southeastern Chubut Province (Argentina) is detailed. Most of the metatherian taxa here described are new for this mammalian assemblage, which in turn is the base of the late Danian (early Paleocene, Peligran Land-mammal-age). Differences between this association and that of Tiupampa, in Bolivia (also of Paleocene age) are remarkable. The former represent a mixture of Gondwanan and Holarctic lineages: monotremes, gondwanatherians, dryolestoids,
metatherians, and eutherians, while those of Tiupampa are strictly therian in nature and with Laurasic affinities. More important than the differences in age between these faunas, we infer a decisive biogeographic influence in the composition of each one of them: the Punta Peligro fauna would be part of an Andean Region (Austral Kingdom) radiation, while that of Tiupampa seems to be more typically Neotropical (Holotropical Kingdom). Metatherians and eutherians from Punta Peligro are more derived than those of Tiupampa, and anticipate several lineages recorded in Eocene levels at other South American localities. The updated list of mammals from the Banco Negro Inferior includes
the following taxa: Prototheria, Monotremata, Ornithorhynchidae: Monotrematum sudamericanum; Allotheria, Gondwanatheria, Sudamericidae: Sudamerica ameghinoi; Cladotheria, Dryolestoidea Peligrotheriidae: Peligrotherium tropicalis; Metatheria, "Ameridelphia", Derorhynchidae: Derorhynchus aff. D. minutus; family indet.: Didelphopsis primaeva sp. nov.; Polydolopimorphia, Bonapartheriidae: Salamancatherium lacerum gen. et sp. nov.; family indet. Alfredocarlinia cratera gen. et sp. nov.; and eventually ?Sparassodonta, family, genus and species indet.Metatheria, order, family, genus and species indet.; Eutheria, Panperissodactyla, Litopterna, Notonychopidae: Requisia vidmari;
Didolodontidae: Raulvaccia peligrensis, Escribania chubutensis, E. talonicuspis.
Keywords. Mammalia, Danian, early Paleocene, Patagonia, Punta Peligro
... South American ecosystems were dramatically affected by the orogeny of the Andean range, which is arguably the most important geological event in the continent with profound repercussions on the physiography, climate, and biota (Hughes and Eastwood, 2006;Hoorn et al., 2010;Antonelli and Sanmartín, 2011;Madriñán et al., 2013;Givnish et al., 2014;Hughes and Atchison, 2015;Lagomarsino et al., 2016;Boschman, 2021). These severe environmental changes that occurred in South America during the late Miocene and Pliocene because of the Andean uplift have been proposed as a plausible hypothesis to explain the Borhyaenoidea extinction (Subclade of Sparassodonta; Jaureguizar, 1986;Pascual and Jaureguizar, 1990;Forasiepi et al., 2007). Global cooling coupled with the rain shadow caused by the increase in the Andes elevation after the Middle Miocene triggered the beginning of Patagonia's desertification and the forest replacement by more open and xerophytic vegetation (Palazzesi et al., 2014). ...
... Global cooling coupled with the rain shadow caused by the increase in the Andes elevation after the Middle Miocene triggered the beginning of Patagonia's desertification and the forest replacement by more open and xerophytic vegetation (Palazzesi et al., 2014). These continental changes impacted mammalian paleo-communities and may have harmed sparassodonts' diversity (Patterson and Pascual, 1968;Pascual et al., 1985;Pascual and Jaureguizar, 1990;Barreda and Palazzesi, 2007;Prevosti and Forasiepi, 2018;Goin et al., 2010;Prevosti et al., 2013). ...
Sparassodonta, a Metatherian monophyletic group, was the main mammalian carnivore predator clade in South America from the Paleogene to the Early Pliocene (c. 66–3.5 Ma). However, there is still no consensus on the causes of their demise. Here, we use the fossil record and Bayesian diversification models to infer the origination and extinction rates for Sparassodonta. Then, we evaluate if their demise can be attributed to global temperature changes, Andean uplift, biotic interactions with their competitor and prey clades, and body mass evolution. That is biotic aspects in the context of the Red Queen model, abiotic aspects in the context of the Court Jester model, and an intrinsic lineage attribute. Our results show that this lineage is characterized by a positive near-zero net diversification rate indicating that the clade maintained a relatively low but stable diversity until the Middle Miocene when an increase in extinction rate drove them to decline and eventual extinction. Moreover, our results support the idea that a drastic regional landscape change triggered by the Andean uplift process affected their diversification dynamics, eventually driving them to extinction. These environmental changes could explicitly affect Sparassodonta lineages due to their ever-present vulnerability to extinction by near-zero net diversification rate and their highly specialized ecology that could have constrained adaptation to new South American landscapes.
... Metatherians, and then placental mammals, were introduced into South America via immigration events from North America that likely began in the latest Cretaceous, at least for the metatherians (see, e.g., Pascual and Ortiz-Jaureguizar, 1990;Woodburne and Case, 1996;Case et al. 2005;Goin et al. in press). However, there is no positive fossil evidence that Marsupialia (crown Metatheria) and Placentalia existed in the Mesozoic of South America. ...
... The main sequence of Eocene mammal faunas in PAT was documented in the Golfo San Jorge Basin (Fig. 11). As summarized by Bond et al. (1995) and Pascual and Ortiz-Jaureguizar (2007) this continental sequences are globally significant due to their extraordinary preservation of South American fossil vertebrate faunas (e.g., Simpson, 1935aSimpson, , 1935bSimpson, , 1948Cifelli, 1985;Pascual and Ortiz-Jaureguizar, 1990;Bond et al., 1995;Flynn and Swisher, 1995;Ortiz-Jaureguizar and Cladera, 2006;Gelfo et al., 2009a;Madden et al., 2010;Woodburne et al., 2014aWoodburne et al., , 2014b, and floras (Berry, 1937;Romero, 1968;Archangelsky, 1973Archangelsky, , 1976Archangelsky, , 1976Petriella and Archangelsky, 1975;Archangelsky and Zamaloa, 1986;Zamaloa and Andreis, 1995;Brea et al., 2005Brea et al., , 2007Brea et al., , 2011Brea et al., , 2007Iglesias et al., 2007;Zucol et al., 2010). ...
The Mesozoic plate tectonic and paleogeographic history of the final break up of West Gondwana had a profound effect on the distribution of terrestrial vertebrates in South America. As the supercontinent fragmented into a series of large landmasses (South America, Antarctica, Australia, New Zealand, the Indian subcontinent, and
Madagascar), particularly during the Late Jurassic and Cretaceous, its terrestrial vertebrates became progressively isolated, evolving into unique faunal assemblages. The episodic nature of South American mammalian Cenozoic faunas became apparent in its modern formulation after George Gaylord Simpson’s seminal works on this topic. Two aspects add complexity to this generally accepted scheme: first, the fact that South America is not (and was not) a biogeographic unit, as the Neotropical Region does not include its southernmost tip (the Andean Region, including Patagonia and the southern Andes). Second, and intimately linked with the first one, that South America was not an island continent during the Late Cretaceous and the beginning of the Cenozoic, being
its southernmost portion closely linked with West Antarctica up to the late Paleocene at least. Here we stress on this second aspect; we summarize a series of recent, detailed paleogeographical analyses of the continental breakup between Patagonia (including the Magallanes Region) and the Antarctic Peninsula crustal block, beginning with the opening of the Atlantic Ocean in the Early Cretaceous and running up to the Early Paleogene
with the expansion of the Scotia Basin. In second place, we comment on the implications of these distinct paleogeographic and paleobiogeographic scenarios (before and after their geographic and faunistic isolation) for the evolution of South American terrestrial mammalian faunas. Summarizing, (1) we recognize a West Weddellian terrestrial biogeographic unit with the assemblage of the southern part of South America (Patagonia and the Magallanes Region) and the Antarctic Peninsula (and probably Thurston Island) crustal block of West Antarctica, spanning from the Late Cretaceous (Campanian) through the Early Paleogene (Paleocene); (2) we suggest that the Antarctic Peninsula acted as a double "Noah’s Ark” regarding, first, the probable migration of some non-therian lineages into southern South America; later, the migration of metatherians to Australasia.
... This precocity was first evident as early as the end of the Paleocene. Independent of body size, it was during the Late Oligocene when many families of notoungulates acquired protohypsodont to hypselodont cheek-teeth (Ortiz-Jaureguizar and Cladera, 2006;Pascual and Jaureguizar, 1990;Pascual and Odreman-Rivas, 1971), and the Tinguirirican (Early Oligocene) fauna of SA is the world's oldest fauna dominated by hypsodont herbivores (Flynn et al., 2003). Recent evidence suggests the existence of several periods of relatively intense evolutionary change in hypsodonty in South American mammals (Madden, 2014;Strömberg et al., 2013), and a general trend for an increased hypsodonty throughout the last 40 Myr has been noted in several notoungulates clades Strömberg et al., 2013). ...
... Therefore, it is also possible to hypothesize that the hypsodonty's long-term evolution was also driven by species sorting (Jablonski, 2008;McShea, 1994). Our results support that species sorting favored high-crown lineages within Toxodontia and Typotheria increase their survivorship during changes in the regional temperature or tectonic settings (Goin et al., 2010;Ortiz-Jaureguizar and Cladera, 2006;Pascual and Jaureguizar, 1990). These results are somewhat consistent with those observed in insular mammals, in which the acquisition of increased hypsodonty allowed them to delay senescence, extend reproductive lifespan, and increase fitness under environments with resource limitations (Jordana et al., 2012). ...
Members of the Order Notoungulata are among the most diverse and common mammals in South America during the Cenozoic. Several lineages within notoungulates (e.g., suborders Typotheria and Toxodontia) show a tendency for increased body sizes and hypsodonty during the last 50 Myr. However, the timing, evolutionary mode, and drivers of such tendencies are not entirely understood. In this paper, we use an extensive database of notoungulate fossil occurrences and body mass and hypsodonty estimates to characterize the evolutionary mode of these two phenotypic traits over time, test the extent to which several factors (e.g., development of open environments in the south of South America) have influenced it through time, and investigate whether large trait values were selected through elevated origination or reduced extinction rates. Our results demonstrate that most of the major notoungulate clades evolved toward larger body sizes (up 1500 kg) and higher tooth crown, from a small and low-crowned tooth ancestor, in a punctuated mode. We also show that body mass and the hypsodonty in typotherians and toxodonts had a coupled evolutionary history. Species sorting was a relevant macroevolutionary process in some notoungulate clades, as taxa with high teeth crown and body mass had lower extinction rates. Finally, the development of the hypsodonty in notoungulates must reflect repeated and quick instances of adaptive responses to the increased availability of volcanic or other terrigenous particles, within the broad context of the SSA Cenozoic Andean mountain building.
... Catena et al., 2017;Croft et al., 2016). This assessment is also supported by discoveries of fossils of herbivorous and frugivorous marsupials (Abderitidae) that were adapted to warm, humid woodlands (Ortiz Jaureguizar, 2003;Pascual & Ortiz Jaureguizar, 1990). Mammal fossils (Xenarthra) and phytoliths from the late to middle Miocene Tafna Formation in the Casira and Calahoyo areas (~22°S, 65.8°W) further support this notion (Quiñones et al., 2019;Zurita et al., 2017). ...
... During this stage in the evolution of what was later to become a plateau region, and well into Miocene time, this part of the southern Central Andes had similar structural and sedimentological characteristics to the Neogene-to-present broken foreland of the Santa Bárbara morphotectonic province farther east (Carrapa et al., 2005;Montero-López et al., 2018;del Papa et al., 2013;Strecker et al., 2007). Climatic and topographic conditions allowed for the existence of a subtropical, humid environment (Catena et al., 2017;Ortiz Jaureguizar, 2003;Pascual & Ortiz Jaureguizar, 1990) and an orographic barrier that would account for the present-day arid conditions of the orogen's interior; the wet eastern flanks of the eastern Andes did not yet exist (Ehlers & Poulsen, 2009;Mulch, Uba, Strecker, Schoenberg, & Chamberlain, 2010;Pingel et al., 2020;Rohrmann et al., 2016;Strecker et al., 2007). The Paleogene steps in the evolution of the region that was to become the Andean Plateau in northern Argentina and southern Bolivia thus generated a pre-strained broken-foreland that subsequently experienced rapid, wholesale uplift accompanied by fundamental topographic and environmental changes in South America (Anderson et al., 2018;Garzione et al., 2008;Strecker et al., 2007). ...
The structural and topographic evolution of orogenic plateaus is an important research topic because of its impact on atmospheric circulation patterns, the amount and distribution of rainfall, and resulting changes in surface processes. The Puna region in the north-western Argentina (between 13ºS and 27ºS) is part of the Andean Plateau, which is the world’s second largest orogenic plateau. In order to investigate the deformational events responsible for the initial growth of this part of the Andean plateau, we carried out structural and stratigraphic investigations within the present-day transition zone between the northern Puna and the adjacent Eastern Cordillera to the east. This transition zone is characterized by ubiquitous exposures of continental middle Eocene redbeds of the Casa Grande Formation. Our structural mapping, together with a sedimentological analysis of these units and their relationships with the adjacent mountain ranges, has revealed growth structures and unconformities that are indicative of syntectonic deposition. These findings support the notion that tectonic shortening in this part of the Central Andes was already active during the middle Paleogene, and that early Cenozoic deformation in the region that now constitutes the Puna occurred in a spatially irregular manner. The patterns of Paleogene deformation and uplift along the eastern margin of the present-day plateau correspond to an approximately north-south oriented swath of reactivated basement heterogeneities (i.e. zones of mechanical weakness) stemming from regional Paleozoic mountain building that may have led to local concentration of deformation belts.
... This interval is globally characterized by strong climatic variation from a general Bgreenhouse^period with pronounced thermal peaks (McInerney and Wing 2011; see data from northwestern Argentina in Hyland et al. 2015Hyland et al. , 2017) and a final cooling triggered at the Eocene-Oligocene boundary (Zachos et al. 2001(Zachos et al. , 2008Livermore et al. 2005). These climatic events led to several biotic changes; among others, the South American metatherians experienced their most notable relative increase in richness during the Cenozoic (Pascual and Ortiz-Jaureguizar 1990;Woodburne et al. 2014;Goin et al. 2019), reaching their highest diversity by the early Eocene (Itaboraian fauna; Oliveira and Goin 2011 and references therein), associated with the warmest global Cenozoic period (Zachos et al. 2008;Hollis et al. 2012). Subsequently, as Bicehouse^conditions became fully established, metatherians underwent a gradual decline in diversity towards the end of the Cenozoic (Goin et al. 2012). ...
... In addition to the particular taxonomic features of this assemblage, this fauna is especially interesting because it evolved in subtropical latitudes and during the Late Eocene Cooling (the interval between the Middle Eocene Climatic Optimum and the Eocene-Oligocene Boundary; see Goin et al. 2016 and references), an uncommon combination of geographical and climatic factors in the context of the evolution of South American Cenozoic mammals. Moreover, this period, included in the Prepatagonian Faunistic Cycle (sensu Pascual and Ortiz-Jaureguizar 1990), is characterized in part by a progressive ecological distinction between the Patagonian and the northern faunas. ...
We describe here a new small bunodont metatherian from Priabonian deposits of the Geste Formation exposed in the Puna of Catamarca Province (Argentina). The material, an isolated right M2?, was recovered by screen-washing techniques and allows us to erect the new species Apeirodon sorianoi. The combination of diagnostic characters includes triangular occlusal pattern, bunoid, with an equally developed stylocone and cusp D, absence of cusp C, protoconal base wide, preparacrista and postmetacrista short, well-developed paracingulum, presence of double rank postvallum-prevallid shear, and presence of small paraconule and larger metaconule that is distolingually located. The overall morphology of Apeirodon more closely resembles Glasbius (particularly G. twitchelli) than any other Cretaceous-Paleogene American metatherian, supporting the largely accepted hypothesis proposing a common origin for some North and South American metatherian lineages. Apeirodon also resembles Reigia punae (another small metatherian recovered from the same stratigraphic levels), Chulpasia, Palangania, and specimens referred to Bobbschaefferia. Tentatively, we propose the inclusion of Apeirodon and Reigia as early divergent members of Polydolopimorphia based on the presence of bunodonty, enlarged stylocone and cusp D, and a distolingually-shifted metaconule. These features, incipiently developed in these late Eocene taxa, are emphasized in later representatives of the order. The presence of a generalized putative polydolopimorphian in Priabonian deposits of northwestern Argentina highlights the key temporal and spatial position of the region in the context of the evolution of Paleogene South American mammals.
... Ameghino, , 1889F. Ameghino, , 1908Patterson, 1952;Simpson, 1940;Pascual et al., 1965;Pascual and Ortiz Jaureguizar, 1990), but also in others (Doering, 1882). Consequently, the Buenos Aires province stands out as one of the most historically researched regions from a paleontological standpoint, owing to the dedicated work of distinguished naturalists, geologists, and paleontologists; with abundant evidence of South American native groups, among others. ...
We present a detailed analysis of the craniomandibular and dental remains of Mesotherium cristatum, the qua-ternary mesotheriid typotherid notoungulate, from Corralito, Santa María Department, Cordoba Province. This population represents the final lineage of Typotheria during middle Pleistocene, Post-Ensenadan Age (>220 ± 13 ka). We compared these new craniomandibular and postcranial samples from Corralito with those from Toscas del Río de La Plata, as well as other localities in the province of Buenos Aires dating to the Ensenadan Age 1.98-0.4 Ma). Our investigation reveals a substantial decline in the size and body mass of the last known population of M. cristatum during the Bonaeran Age period, before its extinction. This occurrence, hitherto un-recorded in any prior South American Land Mammal Age leading up to extinction, might be attributed to the climatic and abiotic changes of the Pleistocene. These changes notably caused a marked reduction in the pale-obiogeographical distribution area ofM. cristatum during the Middle Pleistocene. This size and body mass reduction, possibly an outcome of compelled reproductive isolation, is situated against the context of global cooling and heightened predatory pressures. Moreover, our analysis unveiled distinctive taxonomic attributes specific to this taxon, we compare dental size and find a preliminary evidence of an accelerated tooth replacement pattern. Furthermore, we have effectively updated the faunal composition information of the Corralito deposit, elucidating previous biostratigraphic inferences that had led to the belief of Corralito being an Ense-nadan Age site. This adjustment impacts the first appearance datum (FAD) of the Neolicaphrium recens proter-otheriid litoptern, younger than previously estimated and revised Bonaerian-Lujanian. Finally, this study provides insights into the biological analysis of the iconic species M. cristatum, prevalent in the South American quaternary of the Pampean region. It unreveils new faunal features specific to the Pampean region, shedding light particularly on the lesser-explored western area. These findinngs provide crucial insight into the ever-evolving ecosystem dynamics during the Middle Pleistocene.
... 8). This trend among octodontoids is coincident with the increasing aridity and consequent development of open environments detected on both a regional and global scales (Pascual and Ortiz Jaureguizar 1990;Tripati et al. 2009;Domingo et al. 2020). The climatic change mentioned, which was accompanied by more arid conditions favoured the development of open areas in South America. ...
... The diversification model showed that a reconstructed pulse in temperature change in the mid-Miocene and protracted cooling from the late Miocene onwards led to increasing extinction rates, particularly at higher elevations, peaking in the Pleistocene. Throughout the Americas, Miocene climate change has been associated with changes in vegetation types (Latorre et al. 1997) and faunal turnover (Pascual and Jaureguizar 1990). Specifically, in the southern Andean region, the Miocene saw vast cooling associated with the gradual opening of Drake Passage; the deep ocean channel between southern South America and Antarctica (Mercer 2020). ...
Mountains are among the most biodiverse regions on the planet, and how these landforms shape diversification through the interaction of biological traits and geo-climatic dynamics is integral to understanding global biodiversity. In this study, we investigate the dual roles of climate change and mountain uplift on the evolution of a hyper-diverse radiation, Liolaemus lizards, with a spatially explicit model of diversification using a reconstruction of uplift and paleotemperature in central and southern South America. The diversification model captures a hotspot for Liolaemus around 40°S in lineages with low-dispersal ability and narrow niche breadths. Under the model, speciation rates are highest in low latitudes (<35°S) and mid elevations (~1,000 m), while extinction rates are highest at higher latitudes (>35°S) and higher elevations (>2,000 m). Temperature change through the Cenozoic explained variation in speciation and extinction rates through time and across different elevational bands. Our results point to the conditions of mid elevations being optimal for diversification (i.e., Goldilocks Zone), driven by the combination of (1) a complex topography that facilitates speciation during periods of climatic change, and (2) a relatively moderate climate that enables the persistence of ectothermic lineages and buffers species from extinction.
... The palaeontological significance of the Pampean Region that attracted the attention of Roth and other explorers, relies on its abundant record of fossil vertebrates that documents diversity dynamics and paleoenvironmental change in southern South America and serves as the basis for the South American biochronological scale of the late Neogene and Quaternary (Cione & Tonni, 1995;Cione et al., 2015;Domingo et al., 2020;Gasparini et al., 2023;Pascual & Jaureguizar, 1990;Prado et al., 2021;Prevosti et al., 2021). The Pleistocene was a period of high mammal diversity in the Pampean Region, in particular megafauna, that was affected by paleoenvironmental changes Prado et al., 2001;Prado et al., 2021). ...
The fossil collections made by early explorers in South America have been fundamental to reveal the past diversity of extinct mammals and unravel their evolutionary history. One important early explorer in South America was the Swiss-Argentine palaeontologist Kaspar Jacob Roth, known as Santiago Roth (1850, Herisau, Switzerland-1924, Buenos Aires, Argentina), who made significant collections of fossil mammals that are housed in museums in Europe and Argentina. The important collections of Roth in Switzerland include iconic Pleistocene megafauna from the Pampean Region (Argentina). The palaeontological significance of the Pampean Region relies on its abundant record of fossil vertebrates that documents diversity dynamics and paleoenvironmental change in southern South America, serving as the basis for the South American biostratigraphical scale of the late Neogene and Quaternary. The South American native ungulates (SANUs) were hoofed placental mammals that radiated in South America. The clades Notoungulata and Litopterna include, among others, the last representatives of SANUs megafauna in the continent. We revise and describe for the first time the SANUs specimens from the Pampean Region of the Roth collections in Switzerland. The collections include two species of notoungulates ( Toxodon cf. T. platensis and Mesotherium cristatum ) and one litoptern species ( Macrauchenia patachonica ). The occurrences are restricted to the early and middle Pleistocene (pre-Lujanian Stages/Ages). Although the SANUs diversity in the Roth collections is low in comparison with other groups (e.g., xenarthrans), some of the specimens are very complete, including skulls and postcranial remains. The completeness of the Ma. patachonica material allows an update and reinterpretation of some of the details of the dentition and the postcranial skeleton of this iconic species. In addition to its historical importance, the SANU specimens from the Roth collections provide important information to study the paleobiology and evolution of South American megafauna and evaluate hypotheses about their extinction in the continent.
... This period saw cooler and drier conditions, leading to the establishment of modern climatic conditions. Stable isotope data (δ 18 O and δ 13 C) and mammal assemblages support this trend and confirm an increase in aridity since 16.5-14.5 million years ago in southern Patagonia (Pascual, 1984;Pascual and Jaureguizar, 1990;Blisniuk et al., 2005). This trend is particularly noticeable in the foreland of the studied area (Neuquén Depozone). ...
The Andes offer a distinctive example of the intricate interplay among climate, tectonics, and surface processes. This is exemplified by the mountain range’s north-south orientation, which contrasts with the prevailing East-West wind direction. This interplay controls the uplift evolution of the broken foreland and thus the sediment transfer and erosion from mountain ranges to their forelands. The Neuquén Andes is a peculiar segment of the
southern Central Andes, registering dramatic North-South variabilities in elevation, climate, and tectonic intensities established during the Neogene and Quaternary. In this study, we aimed to identify the tectono-stratigraphic evidence of the Neogene to Quaternary evolution of paleo-environments and drainage networks in the intramountainous basin of Pampa de Agua Amarga in the broken foreland of the southern Neuquén Andes of Argentina.
Starting with a non-depositional and/or erosional phase during the Paleogene, the Pampa de Agua Amarga Basin underwent several phases of syn-orogenic sedimentation in the late Oligocene to early Miocene. The basin gradually shifted from a lacustrine to an alluvial depositional environment, with alluvial deposits becoming
dominant in the mid-Miocene and fluvial deposits dominating in the Pliocene. A significant event occurred during the late Pliocene to early Pleistocene when coarse fluvial deposits were deposited, marking the last aggradation phase. In the early Pleistocene, the onset of incision triggered the drainage system to cut through the
downstream topographic barrier. The excavation of the basin was abrupt, as evidenced by a mid-Pleistocene stepped fluvial terrace and alluvial fan that filled a large canyon across the southern end of the downstream topographic barrier.
The study confirms the regional trend that Miocene basin infill is related to dry climate and high tectonic uplift, which overwhelmed the erosive power of the drainage network. The lowering of tectonic uplift intensity in the southern Neuquén Basin during the Plio-Pleistocene, along with sudden fluctuations in the global colder and wetter climate, ultimately led to the excavation of the intramountainous basin. The Westerlies Wind Belts generate high precipitation rates in the southern Neuquén Andean Cordillera, feeding the Negro River catchment in the retroarc Andean broken foreland. Consequently, the erosive power of the Negro River catchment overcame the declining tectonic uplift, causing significant erosion of the entire broken foreland and Cordillera of the southern Neuquén Andes. Conversely, more intense tectonic uplifts in the northern Neuquén Andes built a more effective orographic barriers that limited precipitation rates of both the Westerlies Wind Belt and South America Summer Monsoon, and preserved the intramountainous basins and mountain interior from erosion.
... Subsequent evolutionary radiation from this generalized putative ancestor led to the occupation of several ecological niches, such as arboreal, fossorial and semi-aquatic niches . Since the late Miocene-Pliocene, the taxonomic and ecological diversification experienced by this clade (Nascimento et al., 2013;Upham et al., 2013;Fabre et al., 2016b;Olivares et al., 2017;Verzi et al., 2018;Piñero et al., 2021) would have been favoured by key geological and climatic events, such as the major uplift of the Andes Mountains, coupled with aridification, the retraction of forests to lower latitudes and the intermittent separation of the Amazon basin from the Atlantic forest owing to the establishment of the South American arid diagonal (Pascual & Ortiz Jaureguizar, 1990;Hoorn et al., 2010;Le Roux, 2012;Palazzesi & Barreda, 2012;Dunn et al., 2015;Machado et al., 2021 and references therein). ...
Brain morphological variation is analysed through virtual endocasts in a highly diversified clade of caviomorph rodents belonging to the family Echimyidae. Diversification in brain size and shape is explored through geometric morphometrics and comparative phylogenetic analyses. The results indicate that brain shape is largely independent of general size and reveal different trends in brain size and shape. Fossorial Euryzygomatominae, arboreal Echimyini and the semi-aquatic Myocastorini Myocastor show high encephalization; the former with a greater contribution from the olfactory bulb and petrosal lobe, and the latter two with a larger surface area of neocortex. The Euryzygomatomyinae and Myocastorini of terrestrial habits show low encephalization with a low contribution of the neocortex. Phylogenetic comparative analyses suggest that endocranial morphological evolution would have been influenced by both phylogeny and locomotor habits. The concurrence of the best fit of the Ornstein–Uhlenbeck model and the significant phylogenetic signal in the datasets suggests the involvement of constraints on morphological diversification within the major clades, as expected under phylogenetic conservatism. This could be explained by an early establishment of a particular endocranial morphology in each major clade, which would have been maintained with relatively little change.
... Indeed, beginning in the late Miocene, litopterns (i.e., macraucheniids and proterotheriids), and notoungulates started experiencing a steep reduction in diversity (i.e., number of genera; Marshall and Cifelli 1990;Croft et al. 2020), and therefore just by chance, the small forms of macraucheniids could have disappeared. There are currently no clear reasons for this general decline in diversity after the late Miocene and towards the Pliocene/Pleistocene, but it could be potentially related to the global cooling and climatic instability triggered by expansions of ice sheets in west-Antarctica and in the Arctic (Zachos et al. 2001) that, coupled with the uplift of the Andes creating rain shadow effects, led to an increase aridification and woodland retreat (Pascual et al. 1985;Pascual and Jaureguizar 1990;Rech et al. 2019). These environmental changes have been also argued as one of the potential causes for the sparassodont demise in the "middle" Pliocene (Chapadmalan SALMA; 3.74-3.04 ...
We describe a new macraucheniine macraucheniid, Micrauchenia saladensis gen. et sp. nov., from the late Miocene (Huayquerian SALMA). This is the first litoptern from Bahía Inglesa Formation, Chile. The specimen includes a partial mandible, cervical and thoracic vertebrae fragments, and portions of the forelimbs (a scapula fragment, an ulna-radius fragment, seven carpals, three metapodials, two proximal phalanges and four intermediate phalanges). The postcranial anatomy of Micrauchenia saladensis is consistent with terrestrial and cursorial locomotion, which suggests an allochthonous position of this specimen within the marine Bahía Inglesa Formation. The fusion of the ulna and radius and the presence of a radial aliform expansion align Micrauchenia with other macraucheniines, with which it shares these features. We interpret the fusion of the ulna and radius as a cursorial specialization and the aliform expansion as an adaptation for strong flexion movements and to resist higher transverse stresses during locomotion. In addition, Micrauchenia saladensis is the smallest member of the subfamily Macraucheniinae. To test the systematics and phylogenetics of this specimen, we expanded previous morphological matrices of macraucheniids by adding one dental and eight postcranial characters and scoring Micrauchenia saladensis . We performed maximum parsimony and Bayesian phylogenetic analyses, the latter applied for the first time to macraucheniid phylogeny. Our analyses confirm Micrauchenia saladensis as a member of the subfamily Macraucheniinae, although with uncertain affinities within this subfamily.
... This model was subsequently modified based mainly in Cenozoic fossiliferous sediments were mainly carried out in Argentina and a minority in other regions of South America (Roth, 1888;Ameghino, 1876Ameghino, , 1889Ameghino, , 1908Doering, 1882Doering, , 1907Kraglievich, 1952;Simpson, 1940b;Marshall et al., 1984). Pascual et al. (1965) modified the term "Mammalian Ages" by that of "land-mammal Ages", which is finally given a formal terminology of "South American Land-Mammal Ages (SALMAs"; see Pascual and Ortiz Jaureguizar, 1990). Cione and Tonni (1995) developed a chronostratigraphic and geochronologic model for the Pleistocene-Holocene stablished as "Ages", that differs conceptually and theoretically from that of the South American Land Mammal Ages (SALMAs). ...
We document a new Last Appearance Datum of the mesotheriine notoungulate Mesotherium cristatum in 220 ± 13 ka, Middle Pleistocene of the west Pampean Region of the Province of Cordoba, Corralito, Santa María Department, Argentina. We increase the previous LAD of this taxon into ca. 530 ka compared to its latest occurrence in Ensenadan Age (ca. 1.95–0.4 Ma; Early-Middle Pleistocene) sediments from the east Pampean Region.
Our detailed literature review of the traditional biostratigraphic support (“Mesotherium cristatum Biozone”) of the Ensenadan Age for the east Pampean Region, and our new temporal record of M. cristatum for the western region of the Pampean Region, .allows us to draw the following conclusions that affect the biostratigraphic model considered so far extensive in South America: (1) M. cristatum should no longer be considered as the guide taxon of the Ensenadan Age; (2) “M. cristatum Biozone” no longer constitutes the biostratigraphic support of the Ensenadan Age as it is also present in sediments of Bonaerian Age; (3) Distinct biostratigraphic units (“M. cristatum Biozone” and “Megatherium americanum Biozone”) overlap in their temporal ranges. In application of the International Stratography Code, we proclaim that the models of chronostratigraphic and biostratigraphic units, established for the Pampean Region, need a strong and consolidated biostratigraphic support, whose temporal limits must be defined by the presence of fossils and not by the temporal limits of the chronostratigraphic units.
This study proclaims the biostratigraphic importance of the western Pampean Region near the Sierras Pampeanas (Córdoba Province) which due to its differential paleoecological conditions and its altitudinal diferenciation with respect to the eastern regions of the Pampean Region could have acted as a faunal reservoir during the Pleistocene.
... According to Scillato-Yané (1975, 1977, 1982, these taxa would be closely related to the extant Euphractus, currently distributed in savanna and forest-edge environments of tropical-subtropical areas (Redford and Wetzel, 1985;de Andrade et al., 2006). In this context, some authors suggested a Chaco-like environment (including partially forested areas, with a marked seasonality) for northwestern Argentina during the Late Miocene-Early Pliocene (Scillato-Yané, 1975, 1977Pascual and Jaureguizar, 1990). This is relevant because the greatest diversity of living armadillos is currently found within the Chaqueño Domain (Vizcaíno et al., 2006, and references therein). ...
The deposits of the Neogene Salicas Formation crop out along the north area and western flanks of the Velasco range, in the northern area of La Rioja Province, Argentina. Previous known remains from the formation include Notoungulata, Litopterna, and Rodentia, in addition to several Xenarthra, including Pilosa (sloths) and Cingulata Glyptodontidae and Dasypodidae. In this contribution, new remains recovered from the Salicas Formation at the area of El Degolladito are described and referred to distinct species of Dasypodidae: Vetelia ghandii Esteban and Nasif 1996, Chasicotatus peiranoi Esteban and Nasif 1996, Chorobates villosissimus (Reig, 1958), Macrochorobates scalabrinii (Moreno and Mercerat, 1891), Paleuphractus argentinus (Moreno and Mercerat, 1891), and Prozaedyus sp. This association of dasypodids increases their diversity for this formation and suggests a Late Miocene age for the bearing levels. Additionally, this association shows great affinities with those reported for other Late Miocene localities along northwestern Argentina, including several species that represent endemic taxa not shared with the Pampean Region. In this context, the differences of Dasypodidae taxa between these regions may be related to both orogenic and paleoambiental features.
... We have to note, though, that there is also evidence for increased aridity over Africa (Retallack 1992;Levin et al. 2006;Eronen et al. 2012;Morales-García et al. 2020), Australia (Stein and Robert 1985;Byrne et al. 2008;Wu et al. 2018), South America (Pascual and Jaureguizar 1990), and some regions of North America (Wolfe 1985;Chamberlain et al. 2014) and Asia (Jiang and Ding 2010;Liu et al. 2009). In the latter, there was an expansion of the arid region from the western to the eastern coast of China, whereas the humid areas were limited to the northern and southern parts (Steininger 1999;Wan et al. 2007;Clift et al. 2014). ...
The relationship between the hydrological cycle and the temperature is rather complex and of great importance to human socioeconomic activities. The prevailing theory suggests that as temperature increases the hydrological cycle is intensified. Practically, this means more and heavier precipitation. However, the exact magnitude of hydrological cycle response and its spatio-temporal characteristics is still under investigation. Looking back in Earth’s hydroclimatic history, it is easy to find some periods where global temperature was substantially different than present. Here, we examine some of these periods to present the current knowledge about past hydrological cycle variability (specifically precipitation), and its relationship to temperature. The periods under investigation are the Mid-Miocene Climate Optimum, the Eemian Interglacial Stage, the Last Glacial Maximum, the Heinrich and Dansgaard–Oeschger Events, the Bølling–Allerød, the Younger Dryas, the 8.2 ka event, the Medieval Climate Anomaly, and the Little Ice Age. We report that the hypothesis that a warmer climate is a wetter climate could be an oversimplification, because the response of water cycle appears to be spatio-temporally heterogeneous.
... 45 million years ago; Goin et al. 2016;Abello et al. 2020Abello et al. , 2021. Evidence from fossils show the evolution of American marsupials was mostly shaped by the paleoclimatic events that occurred during the Cenozoic of South America (Pascual and Ortiz-Jaureguizar 1990;Flynn et al. 2012;Goin et al. 2012Goin et al. , 2016Goin and Martin in press). ...
This is the first study analyzing the distribution of New World marsupials and their relationship to climatic zones on a continental scale. We describe the distribution at different taxonomic categories (order, subfamily, tribe, genus) and their presence within climates, and discuss these patterns considering two different processes: serendipity or adaptation (i.e., a serendipitous process affects a taxon older than the climate it inhabits, or affects a taxon younger than the climate it inhabits but without the evolution of new traits; an adaptation process affects a taxon in a climate with the evolution of new traits). Living Didelphimorphia included the highest richness and least functional redundancy in Tropical climates at the four taxonomic categories studied; living Paucituberculata was mostly represented in Temperate climates, and living Microbiotheria was exclusively represented in Temperate climates. The most restrictive climates grouped generalized forms (e.g., scansorial animalivores) with a high order richness, but high functional redundancy and low richness for all the other taxonomic categories (i.e., subfamily, tribe, genus). Also, climates which favor complex habitats (e.g., tropical, subtropical and temperate forests) have a higher richness and functional redundancy, while simple habitats resulting from drier and/or colder climates have less specialized forms, albeit taxonomically singular (e.g., Lestodelphys, Chacodelphys, Caenolestes). Highly seasonal climates grouped generalized taxa with high functional redundancy, and convergent adaptations (e.g., caudal fat storage, torpor or hibernation), while stable climates over long periods of time, acted as diversification centers for New World marsupials, especially Didelphimorphia.
... In a global perspective, the late Miocene was characterized by important geological and climatic changes that clearly affected terrestrial ecosystems (Zachos 2001;Herbert et al. 2016). This period evidenced a progressive aridification, with the replacement of forested areas by more open biomes with more xerophytic vegetation (Pascual and Ortiz Jaureguizar 1990;Barreda and Palazzesi 2007;Hoorn et al. 2010;Domingo et al. 2020). These events mark the beginning of the "Edad de las planicies australes" (Age of the Southern Plains), which is coincident with the Chasicoan Stage/Age (Ortiz-Jaureguizar 1998; Ortiz-Jaureguizar and Cladera 2006). ...
Glyptodonts (Xenarthra, Cingulata) are one of the most amazing Cenozoic South American mammals, with some terminal forms reaching ca. two tons. The Paleogene record of glyptodonts is still poorly known, although some of their diversification is observable in Patagonian Argentina. Since the early and middle Miocene (ca. 19–13 Ma), two large clades can be recognized in South America. One probably has a northern origin (Glyptodontinae), while the other one, called the “austral clade”, is interpreted to have had an austral origin, with the oldest records represented by the “Propalaehoplophorinae” from the late early Miocene of Patagonian Argentina. In this scenario, the extra-Patagonian radiations are still poorly known, despite their importance for understanding the late Miocene and Pliocene diversity. Here, we carry out a comprehensive revision of late Miocene (Chasicoan Stage/Age) glyptodonts of central Argentina (Buenos Aires and San Juan provinces). Our results show that, contrary to what is traditionally assumed, it was a period of very low diversity, with only one species recognized in this region, Kelenkura castroi gen et sp. nov. Our phylogenetic analysis shows that this species represents the sister taxon of the remaining species of the “austral clade”, representing the first branch of the extra-Patagonian radiation. Additionally, K. castroi is the first taxon showing a “fully modern” morphology of the caudal tube.
... From the late Miocene on, southern fossil echimyids belong to lineages of terrestrial and fossorial Euryzygomatomyinae and Myocastorini (sensu Fabre et al. 2017) that currently inhabit open, shrubby to grassland environments, and dry forests (Reig 1986;Verzi et al. 1994Verzi et al. , 1995Verzi et al. , 2014Verzi et al. , 2016Verzi et al. , 2019Vucetich 1995;Vucetich et al. 1997;Cartelle 1999;Hadler et al. 2008;Olivares et al. 2012bOlivares et al. , 2017Olivares et al. , 2020Sostillo et al. 2015;Candela et al. 2020). This taxonomic composition of the fossil record of echimyids is concurrent with Cenozoic palaeoclimatic changes (Pascual & Ortiz Jaureguizar 1990;Janis 1993;Denton 1999; the forest-adapted lineages and following with the open-adapted ones except for Myocastor (Pascual 1967;Verzi et al. 2018). ...
Echimyidae is the most widely diversified family among hystricognath rodents, both in the number of species and variety of lifestyles. In the Patagonian Subregion of southern South America, extinct echimyids related to living arboreal species (Echimyini) are recorded up to the middle Miocene, whereas all the known southern fossils since the late Miocene are linked to terrestrial and fossorial lineages currently inhabiting the Chacoan open biome in eastern South America. In this work, we describe a new genus of echimyid rodent, Paralonchothrix gen. nov., from the late Miocene of northwestern Argentina and western Brazil. Its single recognised species, Paralonchothrix ponderosus comb. nov., is represented by two hemimandibles. One of them comes from a level of Loma de Las Tapias Formation, underlying a tuff dated at 7.0 ± 0.9 Ma (Huayquerian age, late Miocene); the other specimen comes from the 'Araucanense' of Valle de Santa María (type locality, Huayquerian age, late Miocene). A phylogenetic analysis linked Paralonchothrix to Lonchothrix, both being the sister group to Mesomys. Thereby, for the first time, an echimyid linked to living Amazonian arboreal clades is recognised for the late Miocene of southern South America. Paralonchothrix gen. nov. thus represents an exceptional record that raises the need to review the postulated evolutionary pattern for echimyids recorded at high latitudes since the late Miocene. The new genus provides a minimum age (ca.7 Ma) in the fossil record for the divergence between Mesomys and Lonchothrix. The palaeoenvironmental conditions inferred for the late Miocene in western and northwestern Argentina suggest savanna-type environments, with areas with more closed woodlands in peri-Andean valleys. The record of Paralonchothrix gen. nov. supports the hypothesis that this area would have maintained connections with tropical biomes of northern South America during the late Miocene.
... It is also possible to observe changes in the types of enamel microstructure within toxodonts, with more derived features in protohypsodont and euhypsodont forms (Lindenau 2005;Madden 2015;Fillippo et. al 2019), indicating functional adaptation and the provision of greater resistance to abrasion related to the consumption of more abrasive vegetation (e.g., Simpson 1967;Janis and Fortelius 1988;Pascual and Ortiz-Jaureguizar 1990;Strömberg et al. 2013;Cassini et al. 2017). ...
Enamel microstructure is studied here in Toxodon sp., a notoungulate from the Pleistocene of South America. The material includes 13 specimens from outcrops in São Paulo and Rio Grande do Sul states, Brazil. Analyses of ground sections of upper and lower incisors, premolars, molars, and deciduous premolars by scanning electron microscopy reveal Schmelzmuster with three enamel types: modified radial enamel (MRE), associated with the enamel-dentine junction (EDJ); Hunter-Schreger bands (HSB), an intermediary layer with decussating prisms; and radial enamel (RE), a layer placed next to the outer enamel surface. Microstructural features vary in each tooth category, on the buccal and lingual sides, as well as in the different regions of each tooth. The proportion of RE increases in the occlusal area of I2, which commonly exhibits intense wear, and may be related to abrasion resistance. HSB thickness ranges from 6 to 20 prisms, with the thickest portions placed in areas with intense masticatory loads. The most concentrated packing densities of HSB in the upper incisors and lower premolars suggest these teeth bore the greatest biomechanical demands. Incisors and cheek teeth show differentiation of Schmelzmuster, suggesting dental antagonistic contact areas, as well as leading and trailing edges. Deciduous premolars exhibit enamel in the early stages of development, and a neonatal line is observed almost parallel to the EDJ, possibly related to biological stress during birth. The EDJ is scalloped in all dental categories, with varying sizes and shapes. Larger and more pronounced scallops are observed in I2, i3, p4, and in the enamel folds of the upper and lower cheek teeth, associated with microstructural features indicative of greater biomechanical demands. Microstructural enamel findings presented here corroborate morphological trends in the dentition of Notoungulata related to hypsodonty, providing greater resistance to the consumption of abrasive diets in these euhypsodont-toothed herbivores.
Key words: Mammalia, Toxodontidae, euhypsodont teeth, enamel-dentine junction, Hunter-Schreger bands, neonatal line, Pleistocene, Brazil.
... The studies of fossil vertebrates also suggest a warm climate during the early − middle Miocene of Patagonia due to the presence of Platyrrhini primates and other warm climate-sensitive vertebrates in the Santa Cruz Formation (18-16 Ma, Pascual and Odreman Rivas, 1971;Pascual and Ortiz-Jaureguizar, 1990;Kay et al., 2012), a unit only a few Ma younger than the Río Leona Formation. Hinojosa (2005) estimated MATs of 15.6 (±2.4) and 16.9 (±2.4)°C based on leaf physiognomy for the Cerro Las Águilas and Navidad-Goterones-Matanzas (late Oligocene−early Miocene of central Chile). ...
Patagonia has a rich record of fossil woods that are a unique data store of paleoclimatic information. We studied the wood flora recovered from the Río Leona Formation (early Miocene) of southern Patagonia near El Calafate and Río Turbio localities, Santa Cruz Province, Argentina. The fossil wood assemblage was analyzed using various methodologies (anatomy analysis, Vulnerability and Mesomorphic indices, and the Coexistence Approach) to determine paleoclimate variables including mean annual temperature (MAT) and mean annual precipitation (MAP). The anatomy analysis developed by Wiemann et al. (1998, 1999) is based mostly on woods from the Northern Hemisphere. We applied those equations to extant woods from the southernmost region of South America to test their functionality and to compare them with the results obtained from the fossils. These equations gave limited results. Climate signals from fossil woods suggest a microthermal climate for the region with MAT of 8–12 °C and MAP of 80–170 cm/year. In addition, part of the results points towards an environment with water in abundance (i.e., Coexistence Approach and some wood characters influenced by the environment) and other results suggest wood tolerance to hydric stress (i.e., Vulnerability Index, Mesomorphy Index, and wood characters influenced by the environment). These suggest an environment with rainy and dry seasons, which is also supported by the presence of well-marked growth ring boundaries and false rings. These conditions can be found today in central Chile, a region that shares some vegetation elements with the Río Leona Formation and has a Mediterranean climate.
... Australes' (Age of the Austral Plains; see Ortiz Jaureguizar, 1998;Ortiz Jaureguizar & Cladera, 2006), marked by aridity and open environments (e.g. Pascual & Ortiz Jaureguizar, 1990). It is noteworthy that the aridization and the emergence of grasslands were not coincident with the development of euhypsodonty in the clade, given that hypsodonty is not related with grasses but with grit consumption in the diet (e.g. ...
Rodents are the most diverse order of extant mammals, and caviomorph rodents, or New World hystricognaths, have a remarkable morphological disparity and a long fossil record that begins in the Eocene. Chinchilloidea is a poorly understood clade within Caviomorpha, from an evolutionary and phylogenetic perspective. It includes the extant families Chinchillidae and Dinomyidae, the extinct Neoepiblemidae and Cephalomyidae, and several extinct chinchilloids without a clear phylogenetic position, like Eoincamys, Borikenomys, Chambiramys, Ucayalimys, Incamys, Saremmys, Garridomys and Scotamys. The family Chinchillidae includes the extant Chinchilla and Lagidium, grouped in Chinchillinae, and the only living Lagostominae, Lagostomus maximus. Among extinct chinchillids, Eoviscaccia (early Oligocene‐early Miocene of Argentina, Bolivia and Chile), Prolagostomus (early‐middle Miocene of Argentina, Bolivia and Chile) and Pliolagostomus (early‐middle Miocene of Argentina) are the only genera originally described as members of the family. Based on the study of specimens with unworn or little‐worn cheek teeth, belonging to extinct and extant taxa, we propose homologies of the cheek teeth structures and perform a combined molecular and morphological phylogenetic analysis including extinct and extant taxa of all families of Chinchilloidea and all genera of Chinchillidae. Our phylogenetic analysis recovered three major lineages in the evolutionary history of Chinchilloidea. The first major lineage is composed of the extant taxa Chinchilla, Lagidium and Lagostomus, and the extinct genera Eoviscaccia, Prolagostomus, Pliolagostomus, Garridomys, Incamys, Loncolicu and Saremmys. Cephalomyid (Banderomys, Cephalomys, Litodontomys, Soriamys) and neoepiblemid (Neoepiblema, Perimys, Phoberomys, Scotamys) genera are part of the second major lineage, while dinomyids such as Dinomys, Drytomomys, Scleromys, ‘Scleromys’ and Tetrastylus constitute the third major lineage within Chinchilloidea. The phylogenetic position of some taxa previously considered as incertae sedis chinchilloids or without a clear suprageneric group (i.e. Incamys, Saremmys, Garridomys and Loncolicu) show that they belong to pan‐Chinchillidae and conform the stem Chinchillidae along with Eoviscaccia. The euhypsodont crown Chinchillidae includes the living subfamilies Chinchillinae and Lagostominae. Dinomyidae and Eoincamys pascuali are recovered as the sisters of a major clade composed by ‘Cephalomyidae’+Neopiblemidae and pan‐Chinchillidae, and Chambiramys sylvaticus occupies a basal position to the same clade. Four major radiation events are identified in the evolutionary history of Chinchilloidea. The analysis of new morphological characters linked with molecular evidence as well as the addition of taxa of uncertain or unstable phylogenetic position or not considered in previous studies allowed us resolve part of the relationships within Chinchilloidea, particularly that of Chinchillidae, supporting preceding morphological hypotheses. We studied extinct and extant Chinchilloidea (Rodentia, Caviomorpha), proposing homologies of the cheek teeth structures. A combined molecular and morphological phylogenetic analysis show that some taxa previously considered as chinchilloids without clear affinities belong to pan‐Chinchillidae and conform the stem Chinchillidae along with Eoviscaccia. Crown Chinchillidae includes the living subfamilies Chinchillinae and Lagostominae.
... Accordingly, the uplifting of the ice mantle in the Antarctic Peninsula is well recorded in~9 Ma (Davies et al. 2012) and it can be also inferred that the colder period may have started~14 Ma ago (Blisniuk et al. 2005, Hayllwood et al. 2009). South American fossil faunal evidence also confirms the decrease in temperatures for the Late Miocene (Pascual and Jaureguizar 1990). ...
... These ages were established through the evolutionary degree of the faunas, in part following the same way as Ameghino. Although these units have not been recognized by any stratigraphic code, they have proved to be very useful as an organizational method in the development of concepts about the stratigraphy and evolution of mammals (Simpson 1971;Pascual & Ortiz Jaureguizar 1990). Pascual et al. (1996) suggested that SALMA has proved to be useful for intra-and intercontinental correlations and subdividing Cenozoic time. ...
... Due to notable floristic similarities (Sarmiento, 1975) among the northern Andes, Caatinga and the Caribbean coast in Venezuela and Colombia, in addition to their similar climates, a hypothesis of a historical northern route has been raised (Queiroz & al., 2017). Quaternary climatic fluctuations affected sea level, and when the climate was drier and cooler, the sea level was much lower (Pascual & Jaureguizar, 1990), possibly exposing lands along the northeastern and northern coasts of South America, thus possibly promoting suitable habitats connecting dry areas on the north side of the continent that are separated inland by humid forest (Queiroz & al., 2017). Moreover, edaphic and climatic conditions are prominent forces in the evolutionary histories and biogeographic patterns of SDTF lineages . ...
Seasonally Dry Tropical Forests (SDTFs) are found scattered throughout the Neotropics, from northwestern Mexico to northern Argentina, and southwestern and eastern Brazil, with eastern Brazil having the largest and most isolated fragment of SDTF, known as Caatinga. Growing knowledge from dated phylogenies and ancestral reconstruction studies suggests that SDTF lineages are nested in geographically structured phylogenies with clades highly restricted to each disjunct patch. To address these hypotheses, we investigated the biogeographic history of Euphorbia sect. Brasilienses, a group of succulent spurges from eastern Brazil's SDTF. To this aim, we assembled a concatenated matrix from 126 accessions with four markers (302 sequences from previous studies and 19 newly generated): one nuclear (ITS1) and three plastid (matK, ndhF, trnL‐trnF) loci. Our results showed that clade Brasilienses and its sister group Stachydium diverged from a common ancestor during the Miocene around 16.5 Ma. Clade Stachydium was recovered with a mean crown age of 7.7 Ma, while clade Brasilienses was recovered as a relatively young group that started diversifying about 3.1 Ma. Biogeographic results showed that the ancestral range of the clade Stachydium + Brasilienses comprised the Andes and eastern Brazil's SDTF, therefore suggesting past connections between western and eastern South America. The ancestral range of clade Brasilienses was restricted to eastern Brazil SDTF, which contrasts with clade Stachydium, which was recovered with a broader ancestral range around Late Miocene. Our results suggest limited dispersal abilities, niche conservatisms and an origin for E. sect. Brasilienses pre‐dating the Pleistocene. By contributing to the understanding of the origin and diversification of this group of endemic spurges, our study provides insights into the history of this SDTF in eastern South America.
... This second event was linked to the global climatic drying and the expansion of open habitats (Denton, 1999;Zachos et al., 2001;Barreda & Palazzesi, 2007;Palazzesi & Barreda, 2007;Tripati et al., 2009;Pound et al., 2012;Dunn et al., 2015). In South America, the Andean uplift was also an important factor contributing to this drying trend (Pascual & Ortiz Jaureguizar, 1990;Le Roux, 2012; but see Palazzesi et al., 2014). Interestingly, the optimization of the Oligocene common ancestor of Octodontidae and Ctenomyidae (node 120; Fig. 2; Supporting Information, Figs S2, S3) and of the Late Miocene common ancestors of Ctenomys (node 158) and most of the fossorial octodontids (e.g. ...
Caviomorph rodents constitute a highly diverse clade of Neotropical mammals. They are recorded since at least the late Middle Eocene and have a long and complex evolutionary history. Using geometric morphometric data, we analysed the variation in mandibular shape of this clade through integration analyses, allometry and shape optimizations onto a phylogenetic tree of 104 extant and extinct species. The analyses of shape variation revealed a strong influence of phylogenetic structure and life habits. A remarkable allometric effect was observed for specific mandibular traits. Morphological changes occurring in the alveolar and muscular functional units were moderately associated. Interestingly, the coordinated evolution of these two functional units was decoupled in the clade of extant abrocomids. A sequential and nearly synchronic acquisition of convergent traits has occurred in chinchillids and derived cavioids since at least the early Middle Oligocene, probably derived from grass-feeding habits or similar adaptations to other abrasive items. Convergences between fossorial taxa evolved in two main events through the Oligocene and middle Late Miocene. Morphological analysis of the fossil representatives allowed a better understanding of the timing of trait acquisitions during the evolutionary history of caviomorphs and its relationship with global and regional palaeoenvironmental changes.
... Previously published data indicate that the Miocene climate of Patagonia was characterized by warm and moist conditions. Tropical mammals diversified and expanded south during the Early Miocene (Pascual & Ortiz Jaureguizar, 1990). Patagonia, which had been dominated by a mixture of drier lowlands interspersed with forested riparian areas, saw a southward expansion of megathermal forests reliant on high temperatures (MAT > 24°C; Barreda & Palazzesi, 2007;Dunn et al., 2015;Strömberg et al., 2013). ...
Fossil‐rich sediments of the Santa Cruz Formation, Patagonia, Argentina, span the initiation of the Miocene Climatic Optimum (MCO), the most recent period of warm and wet conditions in the Cenozoic. These conditions drove the expansion of tropical and subtropical ecosystems to much higher latitudes, with the fossiliferous Santa Cruz Formation recording one of the southernmost examples. We collected new carbon and oxygen isotope compositions of herbivore tooth enamel from fossils ~17.4 to 16.4 Ma in age to investigate ecological and climatic changes across the initiation of the MCO. Enamel δ¹³C values are consistent with a C3‐dominated ecosystem with moderate precipitation and a mix of wooded and more open areas. Serially sampled teeth reveal little zoning in δ¹³C and δ¹⁸O values, suggesting little seasonal variation in water and plant isotope compositions or seasonal changes in diet. Carbon isotope‐based estimates of mean annual precipitation (MAP) are consistent with aridification, with MAP decreasing from ~1,000 ± 235 mm/yr at 17.4 Ma to ~525 ± 105 mm/yr at the start of the climatic optimum (~16.9 Ma). This decrease corresponds to increasing global temperatures, as indicated by marine proxy records, and was followed by a rebound to ~840 ± 270 mm/yr by ~16.4 Ma. In comparison to a modern mean annual temperature (MAT) in the region of ~8°C, oxygen isotopes indicate high MAT (at least 20°C) at the onset of the MCO at 16.9 Ma and a significant increase in MAT to ~25°C by 16.4 Ma.
... Abbreviations: Plio., Pliocene; Ple., Pleistocene. turnover at the Oligocene-Miocene boundary (which, notably, marked the end of all non-thylacosmiline proborhyaenids; Bond and Pascual, 1983), the Middle Miocene Climatic Optimum and subsequent climatic deterioration (Croft et al., 2016), and the expansion of grasslands during the late Miocene (Pascual and Ortiz Jaureguizar, 1990). The shorter stratigraphic ranges of placental sabertooths relative to thylacosmilines do not appear to be attributable to competitive interactions between placental sabertooth clades in North America, Eurasia, and Africa compared to the relative isolation of thylacosmilines in South America, as placental sabertooth clades mostly do not overlap in space and time (e.g., North America's "cat gap" of Hunt and Joeckel, 1988). ...
Thylacosmiline sparassodonts (previously recognized as thylacosmilids) are among the most iconic groups of endemic South American Cenozoic mammals due to their distinctive morphology and convergent resemblance to saber-toothed placental carnivores. However, the early evolution of this group and its relationship to other sparassodonts remains poorly understood, primarily because only highly specialized Neogene taxa such as Thylacosmilus, Anachlysictis, and Patagosmilus are well known. Here, we describe a new Paleogene sparassodont, Eomakhaira molossus, from the Cachapoal locality of central Chile, the first sparassodont reported from early Oligocene strata of the Abanico Formation. Eomakhaira shares features with both Neogene thylacosmilines and Paleogene “proborhyaenids,” and phylogenetic analyses recover this taxon as sister to the clade of Patagosmilus + Thylacosmilus. This broader clade, in turn, is nested within the group conventionally termed Proborhyaenidae. Our analyses support prior hypotheses of a close relationship between thylacosmilines and traditionally recognized proborhyaenids and provide the strongest evidence to date that thylacosmilines are proborhyaenids (i.e, the latter name as conventionally used refers to a paraphyletic group). To reflect the internestedness of these taxa, we propose use of Riggs' (1933) original name Thylacosmilinae for the less inclusive grouping and Proborhyaenidae for the more inclusive one. Saber teeth arose just once among metatherians (among thylacosmilines), perhaps reflecting a developmental constraint related to nonreplacement of canines in metatherians; hypselodonty may have relaxed this potential constraint in thylacosmilines. The occurrence of Eomakhaira in strata of early Oligocene age from the Chilean Andes demonstrates that the stratigraphic range of thylacosmilines spanned almost 30 million years, far surpassing those of saber-toothed placental lineages.
... Muitas informações são provenientes do registro da Patagônia argentina, onde depósitos sedimentares marinhos e continentais representam o maior componente da sucessão estratigráfica do Neógeno (Pascual & Ortiz-Jaureguizar 1990. No Mioceno são registradas importantes mudanças climáticas e ambientais associadas ao aumento da temperatura global (Zachos et al. 2008), a flutuações eustáticas dos níveis oceânicos (Miller et al. 2005) Barreda & Palazzesi 2007. ...
The notoungulates are native South American ungulates recorded from the Paleocene to the Pleistocene, and whose diversity declined dramatically during the Pliocene, reaching Central America and North America during the Pleistocene. Notoungulates evolved under the climatic and environmental influence, from archaic lineages, with generalized masticatory apparatus, with complete dentition, without
diastema, and with brachydont premolars and molars, to specialized forms with hypertrophied incisors, simplified occlusal crown patterns and protohypsodont and euhypsodont forms. These communities lived first in warm and humid forest habitats, and later, in relatively temperate grasslands in open habitats with a strong tendency
towards aridization and cooling, throughout the Cenozoic. Besides the evolution of dental macroscopic morphology observed in Notoungulata, it is also possible to observe the evolution of the types of enamel microstructure, by the presence of more derived characteristics in euhypsodont forms, indicating functional adaptation and providing greater resistance to consumption of more abrasive vegetation.
... Despite the wide geographic range of interatheriids, the vast majority of their fossil record derives from the southern third of the continent (i.e., south of ~30° S). This primarily reflects a geographic bias in terrestrial mammal sites in South America, most of which are located in southern Argentina and Chile (Patterson & Pascual, 1968;Pascual & Ortiz-Jaureguizar, 1990). However, this does not entirely explain the known distribution of interatheres. ...
We describe a new interatheriid notoungulate, Juchuysillu arenalesensis gen. et sp. nov., based on six partial upper and lower dentitions from the early to middle Miocene Nazareno Formation of southern Bolivia. A specimen is also referred to J. arenalesensis from the early middle Miocene (Langhian) locality of Cerdas, Bolivia (ca. 100 km to the northwest). The new species is distinguished by its very small size (ca. 15% smaller than Protypotherium minutum) and the unique combination of shallow ectoloph sulci on P3-4, length of M1 > M2 > M3, trapezoidal upper molars, and absence of a buccal talonid sulcus on m3. A second, larger interatheriid species is present at Nazareno but is not represented by remains sufficiently complete for a more precise identification. A phylogenetic analysis indicates that J. arenalesensis represents a unique lineage within Interatheriinae that diverged after Protypotherium sinclairi but before Miocochilius anomopodus, Caenophilus tripartitus, Miocochilius federicoi, and several species of Protypotherium, including Protypotherium australe. Juchuysillu arenalesensis is one of two small (< ca. 3 kg) typotheres at Nazareno; its body mass is estimated at 1.1 kg. An updated faunal list for the Nazareno Formation includes 19 species of mammals pertaining to seven orders and 15 families; fragmentary turtle (Testudinidae?) and bird (Phorusrhacidae) remains are also present. The precise age of Nazareno Formation vertebrates is unknown, but the presence of at least three notoungulate species shared with Cerdas suggests a similar (∼16–15 Ma) age for the fossil-bearing levels.
... In contrast, there are few data for Paleocene climates in the Southern Hemisphere (Woodburne et al., 2013). Early Paleocene climatic considerations with focus on Patagonia come from plant remains (Petriella, 1972;Petriella and Archangelsky, 1975;Brea et al., 2005aBrea et al., , 2005b, 2011Barreda and Palazzesi, 2007;Iglesias et al., 2007;Raigemborn et al., 2009Raigemborn et al., , 2018aScafati et al., 2009), paleofauna (Pascual and Ortiz-Jaureguizar, 1990;Pascual et al., 1996;Gelfo et al., 2009;Bona et al., 2018), and sedimentological evidences (Andreis et al., 1975;Andreis, 1977). Biotic proxies indicate humid and warm conditions, which are consistent with the warm off-shore seawater temperatures inferred from abiotic proxies. ...
Las Violetas Fossil Forest of the Salamanca Formation was a mixed forest of Paleocene age located in the Golfo
San Jorge Basin, central Patagonia of Argentina, which includes conifers (previously studied), dicots and palms.
In the present work, the dicot fossil woods outcropping in one of the fossiliferous levels (L3) of the Salamanca
Formation are described, taxonomically assigned, and their affinities are discussed. They are three new species,
including a new genus related to the Myrtaceae and Laurales. The complete fossiliferous assemblage is used to
infer the climate and environment of the fossil forest. This assemblage represents a parautochtonous fossil plant
association that lived either on the margins of channels or exposed bars in well-drained soils, probably tropical
red-soils, close to their depositional setting (tidal channels and bars of an estuary). Warm and humid conditions
and porous host-rocks favored the silicification of woods and pigmentation with Fe, resulting in yellow-orange
and green fossil woods. We apply growth ring analysis to the conifer woods. For the dicots, wood anatomical
characters influenced by the environment were analyzed, and the Vulnerability and Mesomorphy indices were
used. These methods, comparisons with extant forests and the sedimentology, suggest that the Las Violetas Fossil
Forest was an evergreen forest that developed under uniform growing seasons that ended abruptly, with an abundant
water supply and high mean annual temperatures.
... This second event was linked to the global climatic drying and the expansion of open habitats (Denton, 1999;Zachos et al., 2001;Barreda & Palazzesi, 2007;Palazzesi & Barreda, 2007;Tripati et al., 2009;Pound et al., 2012;Dunn et al., 2015). In South America, the Andean uplift was also an important factor contributing to this drying trend (Pascual & Ortiz Jaureguizar, 1990;Le Roux, 2012; but see Palazzesi et al., 2014). Interestingly, the optimization of the Oligocene common ancestor of Octodontidae and Ctenomyidae (node 120; Fig. 2; Supporting Information, Figs S2, S3) and of the Late Miocene common ancestors of Ctenomys (node 158) and most of the fossorial octodontids (e.g. ...
Caviomorph rodents constitute a highly diverse clade of Neotropical mammals. They are recorded since at least the late Middle Eocene and have a long and complex evolutionary history. Using geometric morphometric data, we analysed the variation in mandibular shape of this clade through integration analyses, allometry and shape optimizations onto a phylogenetic tree of 104 extant and extinct species. The analyses of shape variation revealed a strong influence of phylogenetic structure and life habits. A remarkable allometric effect was observed for specific mandibular traits. Morphological changes occurring in the alveolar and muscular functional units were moderately associated. Interestingly, the coordinated evolution of these two functional units was decoupled in the clade of extant abrocomids. A sequential and nearly synchronic acquisition of convergent traits has occurred in chinchillids and derived cavioids since at least the early Middle Oligocene, probably derived from grass-feeding habits or similar adaptations to other abrasive items. Convergences between fossorial taxa evolved in two main events through the Oligocene and middle Late Miocene. Morphological analysis of the fossil representatives allowed a better understanding of the timing of trait acquisitions during the evolutionary history of caviomorphs and its relationship with global and regional palaeoenvironmental changes.
... Thus, late Miocene could represent a strict minimum age for the origin of the semifossorial genera of echimyids (Galewski et al., 2005;Fabre et al., 2013). The early origin of the semifossorial ecomorphotype within echimyids may have been triggered by the expansion of relatively open and arid environments that arose near the Miocene-Pliocene boundary (Pascual and Ortiz Jaureguizar, 1990;Galewski et al., 2005;Candela and Bonini, 2017). Our results agree with the last resolved phylogeny of the family (Courcelle et al., 2019), where Carterodon is the deep-branching sister group of Capromyinae, in which the most plausible hypothesis related to the semifossorial adaptation likely evolved at least twice within Echimyidae, once along the branch leading to the Proclinodontomys n. gen.-Clyomys-Euryzygomatomys clade, and once along the branch of Carterodontinae. ...
We describe a new extinct spiny rat, Proclinodontomys dondasi n. gen. n. sp. (Rodentia, Caviomorpha, Echimyidae), represented by a noteworthy preserved skull and mandible from the early-middle Pleistocene outcrops at the coastal cliffs of SE Buenos Aires Province (Central Argentina). Phylogenetic analyses allow us to propose that the new species described here and the already known Eurzygomatomys mordax (Winge) represent a new genus closely related to the living Euryzygomatomys spinosus and Clyomys laticeps . The new genus differs from Euryzygomatomys and Clyomys by having much more procumbent upper incisors, a more developed fossa for the M. temporalis, more flared and laterally expanded zygomatic arches, frontal less markedly expanded posteriorly, jugals much deeper anteriorly than posteriorly, with the dorsal border descending more abruptly posteriorly, smaller orbital cavity, and external auditory meatus relatively smaller and slanted upward and backward. Several features of the new species reflect a higher degree of adaptation to semifossorial habits than those of E . spinosus . The origin of the semifossorial ecomorphotype within echimyids may have been triggered by the expansion of relatively open and arid environments that arose near the Miocene-Pliocene boundary. The record of this new echimyid in Central Argentina indicates that during the early-middle Pleistocene, the southern limit of the geographic range of extinct representatives of the Brazilian lineage of semifossorial echimyids extended farther south than that of their living members.
UUID: http://zoobank.org/c30ec1fe-4352-4867-a02f-e0d45c884bfe
... The strong form-function relationship of the dentition of living mammals has allowed paleontologists to make inferences of diet in fossil species (e.g., Van Valkenburgh, 1989;Goin et al., 1992;Prevosti et al., 2013;Zimicz, 2014a;Croft et al., 2018b). Within a historical framework, diet reconstructions are crucial for constructing trophic webs, examining evolutionary changes in lineages, and inferring ancient climates and habitats (Pascual and Jaureguizar, 1990;Van Valkenburgh et al., 2004;Dalerum and Angerbjörn, 2005;Prevosti et al., 2013;Echarri et al., 2017). However, in a recent study, we demonstrated the need to take certain precautions before making inferences, because the morphology of the molar not only correlates with diet but also is influenced by the phylogenetic position of each taxa (Tarquini et al., 2018). ...
Molar morphology is one of the most used proxies for paleoecological inferences in mammals. Since the 19th century, several authors associated some dental morphological traits with the diet of the animal by means of qualitative and descriptive analyses. Later on, since the last century, different studies of tooth function have associated various quantitative traits of tooth shape (i.e., morphometric ratios or angles) with the degree of vertebrate flesh consumed by the animal. However, because different inferences of diet for the same species can be found in the literature, it becomes crucial to carry on studies comparing the power of different proxies. In this work, we compared the utility of classic morphometric indices (RGA, AI and angle α) and three-dimensional landmarks configuration regarding diet inferences. Based on a previously published dataset from our working group, we calculated the classic morphometric indices and performed three classification methods. Our results demonstrate that when using the scores of the landmarks configuration, the diet of species is better reclassified than when using morphometric indices. Furthermore, considering the intraspecific variation when making paleoecological inferences appears fundamental. In the perspective of inferring ecological characteristics to extinct animals, the consideration of the morphological variation in extant organisms is a safeguard to prevent from any misinterpretation in the recontruction of past ecologies.
... Los Xenarthra son un grupo de mamíferos muy particulares y endémicos de la fauna de la Región Neotropical; experimentaron una gran radiación evolutiva, promovida por el aislamiento de América del Sur que dio lugar a una gran diversidad de formas hoy extintas (PASCUAL, 1984;PASCUAL et al., 1984;PASCUAL & ORTIZ-JAUREGUIZAR, 1990;PASCUAL et al., 1996). El primer registro corresponde al Paleoceno tardío de Itaboraí (Rio de Janeiro, Brasil) (SCILLATO- YANÉ, 1976;OLIVEIRA & BERGQVIST, 1998;BERGQVIST et al., 2004). ...
Los Pampatheriidae son una de las familias de mamíferos xenartros nativos de América del Sur. Estos cingulados tuvieron tallas medianas a grandes; los taxones terminales llegaron a pesar más de 250 kg (VIZCAÍNO et al., 1998), cinco veces más que el mayor armadillo actual, Priodontes maximus. Se registran desde el Mustersense (Eoceno tardío) hasta el Holoceno temprano en América del Sur; en América Central solo están representados en el Pleistoceno tardío y en América del Norte desde el Plioceno tardío hasta el Holoceno temprano. Al igual que los gliptodóntidos, son esencialmente herbívoros (WINGE, 1915; VIZCAÍNO et al., 1998). El objetivo de la presente Tesis Doctoral es realizar un estudio sistemático, anatómico y filogenético de los Pampatheriidae, evaluando sus afinidades con otros Cingulata. Tradicionalmente se reconocen seis géneros de Pampatheriidae (sensu SCILLATO-YANÉ, 1980, 1982; EDMUND, 1996; EDMUND & THEODOR, 1997; SCILLATOYANÉ et al., 2005; GÓIS et al., 2012b), considerados válidos por el autor de esta Tesis: Scirrotherium, Kraglievichia, Vassallia, Plaina, Pampatherium y Holmesina. Asimismo, se agregan dos nuevos géneros: Gen. nov. A y Gen. nov. B. Previamente a esta contribución, se reconocían 15 especies, de las cuales 14 resultan válidas. Estas son: 1) Scirrotherium hondaense Edmund, 1997; 2) Kraglievichia paranensis (Ameghino, 1883); 3) Vassallia minuta (Moreno & Mercerat, 1891) 4) Plaina intermedia (Ameghino, 1888); 5) Pl. subintermedia (Rovereto, 1914); 6) Pl. brocherense Castellanos, 1956; 7) Pampatherium humboldtii (Lund, 1839); 8) P. typum Gervais & Ameghino, 1880; 9) P. mexicanum Edmund, 1996; 10) Holmesina major (Lund, 1842); 11) H. septentrionalis (Leidy, 1889); 12) H. occidentalis (Hoffstetter, 1952); 13) H. floridana (Robertson, 1976); y 14) H. paulacoutoi (Cartelle & Bohórquez, 1985). En esta Tesis no se considera válida la especie V. maxima Castellanos, 1946, que pasa ser un sinónimo junior de Pl. intermedia. Además, en el curso del trabajo de Tesis, se reconocieron cuatro nuevas especies (una de las cuales ya fue publicada), a saber: 1) S. carinatum Góis, Scillato-Yané, Carlini & Guilherme (GÓIS et al., en prensa); 2) H. rondoniensis Góis, Scillato-Yané, Carlini & Ubilla (GÓIS et al., 2012b); 3) Gen. nov., sp. nov. A Góis, González Ruiz, Ciancio & Scillato-Yané (en desarrollo); y 4) Gen. nov., sp. nov. B Góis, Scillato-Yané, Ciancio, Gónzalez Ruiz & Soibelzon (en desarrollo). Cabe resaltar que de las cuatro especies nuevas mencionadas anteriormente, dos corresponden a géneros nuevos. De ellos, el Gen. nov., sp. nov. A es hasta el momento el taxón más antiguo conocido para la familia; previamente, los registros más antiguos eran los del Mioceno medio de La Venta, Colombia. El Gen. nov., sp. nov. B es el tercer género que se reconoce para el Pleistoceno de Argentina. Estos dos nuevos géneros y especies, así como las otras dos especies nuevas, incrementan la diversidad de los Pampatheriidae de América del Sur. Probablemente, Argentina fue uno de los centros de diversificación para el citado grupo. Otro resultado obtenido en esta Tesis Doctoral fue la identificación de tres nuevos registros para la Argentina de especies ya conocidas en otros ámbitos, a saber: P. humboldtii, para la provincia de Buenos Aires, y H. majus y H. occidentalis para la provincia de Santa Fe. Dado que la gran mayoría de las especies estaban pobremente descriptas, se procedió a un nuevo tratamiento de ellas: nuevas diagnosis, descripciones e ilustraciones. Como consecuencia, se mejoró notablemente la caracterización morfológica de los géneros y especies que se reconocieron como válidos. Esta situación lleva a cuestionar la validez de algunas especies nominales presentes en la bibliografía. Con los estudios que se están llevando a cabo se ha logrado avanzar en el conocimiento de la anatomía de este grupo. De tal manera, se corrigen, completan y renuevan las descripciones para estos taxones, estudiando la totalidad accesible de los caracteres anatómicos: coraza con sus osteodermos, cráneo, dentición y postcráneo. En síntesis, se ha logrado un conocimiento actualizado de la nomenclatura, anatomía y sistemática de las especies de Pampatheriidae. Uno de los resultados más importantes de esta Tesis, fue el desarrollo de una nueva nomenclatura estándar de los osteodermos para la familia. En tal sentido, los nombres de las estructuras empleados antiguamente resultaban erróneos y confusos desde una perspectiva conceptual. El análisis filogenético realizado evidencia que los Pampatheriidae son un grupo monofilético y están relacionados con los Glyptodontidae, conformando el clado Glyptodontoidea. Además, se confirma la monofilia de Dasypodidae, siendo Peltephilus el grupo hermano de Dasypodidae, ubicándose Peltephilus y Dasypodidae en un clado mayor, los Dasypodoidea. En este análisis se obtiene como otro resultado interesante la exclusión de Proeutatus y Eutatus como el grupo hermano de los GlyptodontoideaLa familia Pampatheriidae queda definida por siete sinapormofías, de las cuales cinco son exclusivas. Vassallia, Plaina y Pampatherium comparten una única sinapomorfía: la elevación central longitudinal de los osteodermos es aplanada. En esta Tesis, se confirman algunas propuestas previas, i.e. la relación Vassallia–Pampatherium (SCILLATO-YANÉ, 1980; SCILLATO-YANÉ et al., 2005), pero con una nueva interpretación: Vassallia es el grupo hermano del clado Plaina–Pampatherium. El clado Pampatherium se encuentra bien soportado, dado que cuenta con seis sinapomorfías. El clado Kraglievichia–Holmesina (excepto H. floridanus) se sostiene a base de tres sinapomorfías. La ubicación de H. floridanus en este clado determina que el género Holmesina sea polifilético.
Sparassodonts were the apex mammalian predators of South America throughout most of the Cenozoic, diversifying into a wide array of niches including fox-like and even saber-toothed forms. Their extinction is still controversial, with different authors suggesting competition with other predators (placental carnivorans, terror birds, and carnivorous opossums), extinction of prey, and climate change as causal explanations. Here, we analyse these hypotheses using a novel approach implicating Bayesian analyses. We find that speciation and extinction rates of sparassodonts can be correlated with (i) intrinsic biotic factors such as changes in body mass and diversity of sparassodonts, (ii) extrinsic biotic factors such as potential prey diversity, and iii) extrinsic abiotic factors like the atmospheric CO 2 , sea level, temperature, and uplift of the Andes. Thus, sparassodonts are a good example of a multilevel mixed model of evolution, where various factors drove the evolutionary history of this clade in a pluralistic way. There is no evidence for competition between Sparassodonta and others predators, and the effect of competition in the face of extinctions of fossil species should be tested and not assumed. Furthermore, we propose a novel approach for evaluating the fossil record when performing macroevolutionary analyses.
Esta breve nota describe el hallazgo de la localidad fosilífera Cañadón del Tordillo, portadora de vertebrados del Friasense, última expresión en Patagonia de una rica fauna subtropical que caracterizó el Mioceno. La localidad, abundante en equímidos, ofidios, armadillos y hasta algún primate, fue luego fuertemente explotada por personal del Museo de La Plata y los materiales obtenidos derivaron en no pocas publicaciones que cambiaron nuestra percepción faunística y ambiental del Friasense.
Read-only version: https://onlinelibrary.wiley.com/share/author/J39BSPUMDFDQAGW3XQPP?target=10.1002/spp2.1368 ------------ Abstract. We analyse the taxonomic status and diversity of the late Miocene Octodontoidea (Hystricognathi) Cercomys primitiva and related samples, a taxon previously known only from the holotype specimen. New findings associated with an extensive review of late Miocene and early Pliocene rodents have allowed us to recognize the occurrence of this and other related species in several localities of central and western Argentina, and in south‐central Bolivia. We discuss the invalidity of Cercomys and propose the new genus Metacaremys, which includes the type species Metacaremys primitiva comb. nov. and two new species, Metacaremys calfucalel sp. nov. and Metacaremys dimi sp. nov. Osteological, brain and dental morphology show that the new genus is not related to Brazilian Echimyidae, as previously considered, but to the southern family Octodontidae. Although the molar morphology of this genus is quite conservative, comparison of the samples shows a variation in size. We discuss the plausible evolutionary pattern explaining this variation and the implied biochronological and biostratigraphical information. It is recognized as an anagenetic lineage in which an increase in size occurs from the oldest species, M. primitiva comb. nov. (early late Miocene, c. 9.23 Ma), to the youngest species, M. dimi sp. nov. (Miocene–Pliocene boundary, c. 5.28 Ma). Metacaremys calfucalel is intermediate in size and age between these two species. The polarity of this pattern of change is consistent with that shown by other partially synchronous independent lineages of octodontoids, thus providing new evidence for the biochronological and biostratigraphic scheme of the late Miocene and early Pliocene of southern South America.
Taxonomic disparity between close clades is one of the most amazing feature of
biodiversity. A clear example is the rodent subfamily Sigmodontinae (near of 400 species)
and its sister subfamily Tylomyinae (10 species). Tylomyinae is composed by exclusively
arboreal rodents, while Sigmodontinae comprises species with different locomotion types.
For the latter, the most diverse clades are also the richest in cursorial species, that is runner
species associated to open vegetation habitats, environments that covered the major part
of South America during the Upper Miocene. This geological epoch signs the begin of
sigmodontine radiation. Thus, in this research I propose that the cursoriality in
Sigmodontinae acted as a innovación clave triggering the fast generation of new lineages.
This hypothesis predicts that the ancestral lineage inhabited open areas; the temporal
origin of cursoriality is between the Tylomyinae-Sigmodontinae divergence and the
sigmodontine MRCA; and that there is a significant association between cursoriality and
diversification. To assess these predictions, a time-calibrated phylogeny was reconstructed
to infer the diversification pattern for this subfamily allowing to estimate the ancestral
states of the ecomorphological traits and the habitat type, and to evaluate the association
between the cursoriality and diversification. The results obtained reject the hypothesis
proposed due to the non-temporal correspondence of the events, since the cursoriality has
a previous origin to the Tylomyinae-Sigmdontinae diversification (11.6 M.y.). Additionally,
there is not relationship between cursoriality and the Sigmodontinae diversification. Even
so, I propose that cursoriality could have an indirect effect, from the Middle Miocene,
allowing the macroevolutionary success of the sigmodontinae rodents once the open
environments in South America emerged. In this scenario there would be a direct relation
of the diversification with the geographical context rather than with the intrinsic trait
evaluated.
A new assemblage of large insect trace fossils is recognized in paleosols of the middle Miocene pyroclastic deposits from extra-Andean north Patagonia. This assemblage includes Racemusichnus jacobacciensis igen. isp. nov., the largest trace fossil in paleosols attributed to solitary insects. R. jacobacciensis is represented by clusters of two to seven thickly walled cylinders horizontally orientated in the paleosol. The cluster arrangement, its orientation, the large size and wall of the cylinders suggest a dung beetle, probably a representative of the Geotrupidae as the possible trace maker. The new ichnoassemblage, also comprising large-sized specimens of Coprinisphaera ispp., Teisseirei barattinia and Feoichnus challa, belongs to the Rosellichnus assemblage-SAPIA of the Coprinisphaera Ichnofacies. Mollic paleosols along with the trace fossils, mammal remains and previous data for this unit suggest an open grassy habitat compatible with high productive grass savannas, under a temperate-warm and seasonal subhumid climate. This assemblage of large-sized trace fossils is attributed to highly productive ecosystems related to the rise of temperature occurred during the Middle Miocene Climatic Optimum.
Historical processes may result in patterns of differentiation among extant populations, which may lead to diversification and speciation. This is often expressed, and measured, as genetic and behavioral variation among populations. Suboscine birds acquire songs by innate mechanisms and are typically poorly studied relative to oscine birds, which may learn songs and thus develop unique dialects among populations. Behavioral features, including song, are extensively used to describe the structure and geographical variation in bird populations. In turn, this knowledge may shed light onto patterns of species diversification across ecoregions, which is particularly relevant in endemic species. Here we investigate for the first time song structure and variation in the Silvery-cheeked Antshrike, an endemic bird of a poorly studied South American dry forest, the Caatinga. We evaluate hypotheses for song diversification, correlating vocal acoustic parameters with geographic patterns and environmental variables. We measured temporal and spectral variables in the song of Sakesphorus cristatus across 14 localities spanning almost the entire range of the species’ distribution. The song presents a clear geographic pattern, and vocal variation was congruent with a barrier by the São Francisco River superimposed to a latitudinal clinal variation that was uncorrelated to climate variables. We argue that these regional differences may have a genetic basis since S. cristatus is a suboscine antbird that should not show song learning (social adaptation) and, apparently, does not have the song correlated to habitat features (acoustic adaptation). More detailed studies are required to test further hypotheses about the drivers of this potential genetic variation underlying the geographical variation in this suboscine bird song.
The Kibenikhoria and Ernestokokenia local faunas were described in the 1930s by George G. Simpson, who defined them as two chronologically consecutive faunas based on a comparison with the Casamayoran South American Land Mammal Age (SALMA). Later, in the 1980?s, both faunas were respectively the basis of the Itaboraian and Riochican SALMAs, a scheme broadly accepted since more than eight decades. However, a systematic revision of their native ungulates is still lacking. In this contribution, we study several collections performed in the classic localities of Cañadón Hondo and Bajo Palangana (southeastern South America), and discuss the systematic status of the mammals listed in their faunas. Our results allow to: (1) assert that the beds containing the mammal associations in Cañadón Hondo and Bajo Palangana locate in the the upper Las Flores Formation and are essentially contemporaneous, (2) improve the knowledge for Kibenikhoria get and Henricosbornia lophodonta, (3) propose H. waitehor and?Peripantostylops orehor are synonymous names of H. lophodonta, and (4) recognize Shecenia ctirneru, Seudenius cteronc, and Pospithecus as Trigonostylopidae aff. Trigonostylops. The Kibenikhoria and Ernestokokenia faunas have six genera in common; five of them are shared with the lower levels of the Sarmiento Formation, whereas K. get, Isotemnus ctalego, Pliodolops winecage, and Gasternia ctalehor are exclusive taxa. Here, the Riochican sensu stricto from Marshall is used to include both local faunas, which represents a distinct and more derived fauna than that from the Itaboraí Formation, but witha less advanced evolutive stage than the lower Sarmiento Formation.
Echimyidae is a species‐rich clade of Neotropical rodents, which diversified in association with forested biomes. Since the late Miocene, a few lineages from southern South America have been adapted to open environments. Eumysops is one of these southern echimyids, and its peculiar craniomandibular morphology has been assumed to be a result of adaptation to open environments. We performed a geometric morphometric analysis of craniomandibular shape variation to explore whether, as suspected, Eumysops is divergent from other echimyids and octodontoids. In addition, we explored whether deterministic factors driven by different ecological dimensions can explain the diversification of shape among octodontoids. We found that craniomandibular shape variation in octodontoids was related to ecological variables. Comparing competing evolutionary models suggested that the input of selective factors play a key role in octodontoid craniomandibular shape diversification; habitat and habits were found to be the most influential factors. In the analysed morphospaces, Eumysops was located distant from other echimyids due to its distinctive traits, especially wide and posteriorly displaced orbits, and related low craniomandibular joint. Divergent orbits and resulting wider panoramic vision support the interpretation of Eumysops as an open‐habitat specialist echimyid. But what is more relevant, is that Eumysops occupied a sector of the octodontoid cranial morphospace not filled by living representatives; this highlights the contribution of fossils in providing key information on the specialization boundaries explored by a clade throughout its history.
Describes a rare thanatocenosis belonging to the marine Las Escobas Fm (Holocene). The sediments correspond to an intertidal environment. The rodents and the amphisbenid are allochthonous, probably carried by continental waters. -from Authors
