No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Miocene Marine Transgressions: Paleoenvironments and Paleobiodiversity
Abstract
Two major marine transgressions covered part of Patagonia during the Miocene and both are recorded in the Península Valdés region. The older (early Miocene) is represented by the volumetrically scarce outcrops of the Gaiman Formation, composed by shelf mudstones and fine sandstones. The late Miocene transgression is represented by the Puerto Madryn Formation, widely distributed in Península Valdés and composed of mudstones, sandstones and shell beds, being the focus of this work. Sediments of this unit were deposited in inner shelf, nearshore, tidal channel and tidal flat environments. Fossil content is abundant and diverse, including palynomorphs, foraminifers, marine invertebrates (dominated by molluscs), cetaceans, pinnipeds, marine fishes and birds, as well as continental mammals, birds, and fishes. Isotopic and biostratigraphical data suggest a late Miocene age for the Puerto Madryn Formation, although some middle Miocene biostratigraphical indicators are present. Paleoenvironmental information suggests oceanic and continental temperatures warmer than present day, evidenced by the Caribbean molluscan association and the continental vertebrate and palinological associations, respectively. Instead, cetaceans, dinoflagellates, and some marine fishes, suggest colder oceanic temperatures. Precipitations were also higher than present, evidenced by the presence of freshwater mammals, birds, fishes, and plants. This work highlighted some gaps in the geological and paleontological knowledge including geochronology, stratigraphic control of paleontological studies and the knowledge of poorly known fossil groups, which should be the focus of future investigations.
... Miocene marine rocks are widespread and well-exposed along coastal cliffs of the Península Valdés and are included in two lithostratigraphic units: the Lower Miocene Gaiman Formation and the Upper Miocene PMF. Both units were deposited during two regional marine sedimentation phases that flooded the study area and many other parts of Patagonia: the early Miocene "Patagoniense" (Parras and Cuitiño 2021) and the Late Miocene "Paranense" (¼ "Entrerriense") (Malumián and Náñez 2011;Cuitiño et al. 2017;del Río et al. 2018). In addition, a recent work confirms an important hiatus of about 4 Myr of duration occurred in the Middle Miocene. ...
... ciconiiform birds, and xenarthrans lithoptern and rodent mammals), trace fossils (belonging to the Cruziana and Skolithos ichnofacies) and palynomorphs (spores, pollen and dinoflagellates) (Cuitiño et al. 2017 and references therein;Viglino et al. 2021). Cuitiño et al. (2017) proposed a three-fold division of the PMF, including, from base to top, a transgressive phase, a maximum-flooding phase, and a regressive phase. Additionally, lower hierarchy stratigraphic cycles are recognized throughout the succession, and interpreted as lower hierarchy sea-level fluctuations. ...
... According to sedimentological observations and lateral correlation with other nearby localities (e.g., Punta Quiroga; Fig. 2B), the horizons studied here correspond to the lower part of the PMF, during the Transgressive and/or Maximum Flooding phases. This part of the succession has been interpreted as a storm-influenced mid-to inner shelf, while the overlying regressive phase has been interpreted to represent shoreface and estuarine settings, with tidal flat, tidal channel, and subtidal bar sub-environments (Scasso and del Río 1987;del Río et al. 2001;Cuitiño et al. 2017). ...
Fieldwork at Península Valdés (Chubut, Argentina) in the Puerto Madryn Formation (Late Miocene) resulted in the discovery of a well-preserved, almost fully articulated, baleen whale (Cetacea, Mysticeti). This specimen, one of the most complete balaenid skeletons known from the Neogene of Argentina and worldwide, was the focus of a taphonomic analysis employing a multidisciplinary approach, integrating taxonomic, sedimentological, stratigraphic, and ichnological analyses, with the aim of reconstructing the taphonomic processes and the paleoenvironmental conditions that controlled preservation of the specimen. The skeleton belongs to the family Balaenidae (right whales). It displays a high degree of articulation, moderate pre-burial fragmentation, and relatively high completeness. Our results suggest that after death, the balaenid suffered a brief biostratinomic phase that can be summarized in four stages: (1) death at sea, with initial decomposition and positive buoyancy of the carcass; (2) internal accumulation of putrefaction gases, re-orientation, then gas loss; (3) sinking and deposition in a ventral-up position on the sea floor of the inner shelf; and (4) lateral re-orientation of the postcranial region due to physical and biological processes. The high degree of articulation and association of the skeletal elements, and the presence of both mandibles, indicate no lateral transport on the seabed and excludes refloating of the carcass at any stage. Finally, the data indicate a low-energy shelf environment with normal marine benthic oxygenation and salinity conditions, characterized by a soft bottom and a moderate sedimentation rate. The last, combined with high bioturbation, plus scour-induced self-burial, resulted in rapid burial of the carcass.
... Some of these units can be correlated with other well-known formations outcropping on the northern Patagonian coast (e.g. Cuitiño et al. 2017). On the other hand, the formations that crop out in the Pen ınsula Vald es region as small isolated exposures are difficult to date. ...
... penguins, cetaceans) ). There is a lack of chronologic calibration and detailed biostratigraphic analysis for the Gaiman Formation; thus, the age of this unit is based on stratigraphic correlation with other regions of Patagonia, which might indicate an approximate Early Miocene age, probably Burdigalian (Parras et al. 2012;Cuitiño et al. 2015bCuitiño et al. , 2017Cuitiño et al. , 2019Parras and Cuitiño 2021). ...
... It is characterized by a highly diversified and abundant macrofossil content, dominated by marine invertebrates, predominantly mollusks (e.g. del R ıo 1990; del Based on the study of diverse fossil groups (mollusks, ostracods, foraminifera, calcareous nannofossils, pollen grains, dinoflagellate cysts, mammals, birds, and fishes), the Puerto Madryn Formation was assigned to the Middle Miocene (del R ıo 1988, 1990Cozzuol 1993;Riva Rossi and Cozzuol 1996;Riva Rossi 1997) and the Upper Miocene (Malumi an and Masiuk 1973;Masiuk et al. 1976;Malumi an 1978;Cione and Tonni 1981;del R ıo 2000;Dozo et al. 2002;Palazzesi and Barreda 2004;Marengo 2015;Fuentes et al. 2016Fuentes et al. , 2018Cuitiño et al. 2017). The strontium ( 87 Sr/ 86 Sr) isotope values of pectinid shells indicated an age of 10.0 ± 0.3 Ma (early Late Miocene) (Scasso et al. 1999. ...
The present work documents the stratigraphic distribution of dinoflagellate cysts from the upper part (60-585 m) of the YPF.Ch. PV. es-1 borehole, Península Valdés, Argentina. The assemblages exhibit a relatively moderate to low diversity. Most samples are characterized by frequent to abundant taxa of the order Gonyaulacales, such as Spiniferites/Achomosphaera spp., Reticulatosphaera actinocoronata, Operculodinium centrocarpum, and Melitasphaeridium choanophorum. Furthermore, a continuous succession of Lower Miocene-Upper Miocene diagnostic dinoflagellate cyst events was recorded for the first time from the Península Valdés region. Eight diagnostic events of highest occurrences (HOs) of dinoflagellate taxa are identified. These bioevents allowed a subdivision of the sedimentary succession into two well-defined stratigraphic sections: Lower to Middle Miocene (Burdigalian-Langhian/probably Serravalian, 430/425–330/325 m) based on the HOs of Emmetrocysta urnaformis, Cannosphaeropsis quattrocchiae, Cousteadinium auybriae, and Cleistosphaeridium ancyreum, and Upper Miocene (Tortonian-Messinian, between 175-170 and 80/85m) based on the HOs of Labyrinthodinium truncatum subsp. truncatum, Operculodinium piaseckii, and Reticulatosphaera actinocoronata. The range of these taxa is compared with well-documented information on Neogene dinoflagellate cysts recorded from different sites across the North and South Atlantic Oceans and adjacent seas. In general, the dinoflagellate cyst assemblages, as well as the selected diagnostic taxa, exhibits a clear similarity with those of the Northern Hemisphere. The only exception is Hystrichokolpoma rigaudiae, which is asynchronous, possibly indicating local paleoenvironmental conditions.
... An Early Miocene age was also estimated based on stratigraphic correlation to better-dated equivalent units (Cuitiño et al., 2015), as well as from palynological assemblage (Palazzesi et al., 2006). The paleontological content of the GF includes poorly-preserved macroinvertebrates, trace fossils, and marine vertebrates, especially cetaceans (Scasso & Castro, 1999;Cuitiño et al., 2017Cuitiño et al., , 2019. ...
... The PMF (Haller, 1979) is composed of mudstones, sandstones, tuffs, and shell beds, interpreted as accumulated in a marine inner shelf to an estuarine environment with a strong tidal influence (Scasso & del Río, 1987;Cuitiño et al., 2017;Fuentes et al., 2019). A latest Serravalian to Tortonian age was assigned for the PMF based on biostratigraphy (Fuentes et al., 2019) and Sr 87 /Sr 86 datings (Scasso et al., 2001;del Río et al., 2018). ...
... A latest Serravalian to Tortonian age was assigned for the PMF based on biostratigraphy (Fuentes et al., 2019) and Sr 87 /Sr 86 datings (Scasso et al., 2001;del Río et al., 2018). The paleontological content of PMF includes an abundant and well-preserved invertebrate macrofauna (del Río, 2000;Cuitiño et al., 2017) and also palynomorphs (Palazzesi & Barreda, 2004), foraminifers (Marengo, 2015), dinoflagellates (Fuentes et al., 2019), and some marine and continental vertebrates (Dozo et al., 2010;Cuitiño et al., 2017), showing a large variety of paleoenvironmental conditions. The GF and PMF are part of the stratigraphic record of the western part of the Valdés Basin, the depocenter of which is located on the Argentinian continental shelf (Continanzia et al., 2011). ...
A 209 m-thick sedimentary succession exposed at Estancia Redonda Chica locality (northeastern Patagonia, Argentina) includes both the Gaiman Formation (Early Miocene) and the Puerto Madryn Formation (Late Miocene). Based on the sedimentologic analysis, the Gaiman Formation is interpreted as accumulated in a marine inner shelf to shoreline environment, whereas an estuarine to terrestrial environment is interpreted for the Puerto Madryn Formation. Fifteen samples were processed and analyzed for diatoms, providing for the first time a micropaleontological record for these units, allowing us to go deeper into the paleoenvironmental interpretations. Fourteen diatom species, two diatom genera, and chrysophyte stomatocysts were identified. The dominant diatom elements among the samples are Paralia sulcata, Lemnicola hungarica, Cocconeis placentula, and Pseudopodosira sp., together with chrysophyte stomatocysts. Paleoecological information drawn from diatom assemblages is consistent with paleoenvironmental interpretations based on sedimentological analysis for both units. However, diatom analysis for the Gaiman Formation suggests a strong freshwater influence in an inner shelf environment, which went unnoticed by utilizing other proxies. We suggest a high-productivity marine zone may have developed as a consequence of nutrient supply from rivers favoring diatom growth. This could explain the unique great abundance of macroinvertebrates and marine vertebrates preserved in the sedimentary succession.
Se estudió una sucesión sedimentaria de 209 metros de espesor, la cual aflora en la localidad de Estancia Redonda Chica (noreste de Patagonia, Argentina). Dicha sucesión expone los depósitos de la Formación Gaiman (Mioceno Temprano) y de la Formación Puerto Madryn (Mioceno Tardío). La Formación Gaiman corresponde a depósitos de plataforma marina interna hasta un ambiente más cercano a la costa. Por otro lado, la Formación Puerto Madryn es interpretada como depósitos de ambientes estuarinos a terrestres. Quince muestras fueron procesadas y analizadas con el objetivo de constatar la presencia de diatomeas y proporcionar, por primera vez, un registro micropaleontológico para la localidad, y a su vez, profundizar la interpretación paleoambiental de los depósitos neógenos de Patagonia. Se pudieron reconocer 14 especies y dos géneros de diatomeas, y estomatoquistes de crisofitas. Las especies Paralia sulcata, Lemnicola hungarica y Cocconeis placentula, y Pseudopodosira sp., junto con los estomatoquistes de crisofitas son dominantes. La información paleoecológica extraída de los ensambles de diatomeas es consistente con la interpretación paleoambiental previamente realizada a partir del análisis sedimentológico para ambas unidades. Sin embargo, la fuerte influencia de agua dulce observada para la Formación Gaiman a partir del análisis diatomológico, aparece como una nueva evidencia para dicha unidad. Se sugiere el posible desarrollo de una zona marina de alta productividad como consecuencia del aporte de nutrientes desde los ríos, favoreciendo el crecimiento de diatomeas lo cual, a su vez, podría explicar la gran abundancia de macroinvertebrados y vertebrados marinos presentes en los depósitos analizados.
... The Puerto Madryn Formation unconformably overlies the Gaiman Formation (Scasso and del Río, 1987). It is composed of a variety of lithologies, such as bioclastic sandstones, bioturbated muddy sandstones, cross-bedded sandstones, heterolithic beds, laminated mudstones, and minor tuffs (Scasso and del Río, 1987;Cuitiño et al., 2017). The age of this unit in the Península Valdés area is relatively wellconstrained based on Sr isotope analyses, suggesting a late Miocene, mostly Tortonian age (11.4-9.4 ...
... The Puerto Madryn Formation is composed of a complex succession of well-stratified lithologies including bioturbated or laminated mudstones, bioturbated or cross-stratified sandstones, bioturbated tuffa- ceous muddy sandstones, massive tuffs, and bioturbated or crossstratified shell beds. Gray sandstones with parallel or ripple lamination or cross-stratification are one of the characteristic features of this unit, and appear as a common element in the upper, regressive part of the unit (Scasso and del Río, 1987;Scasso et al., 2012;Cuitiño et al., 2017;Scasso and Cuitiño, 2017). They are dominated by lithic particles and plagioclase, with subordinated quartz. ...
... Hornblende and pyroxene may compose up to 10% of this sediment, or appear as accessories together with opaque minerals (Marengo, 2015). The Puerto Madryn Formation accumulated in inner shelf, shoreface, and estuarine depositional settings, showing a transgressive-regressive stratigraphic trend (Scasso and del Río, 1987;Scasso et al., 2012;Cuitiño et al., 2017;Scasso and Cuitiño, 2017;Fuentes et al., 2019). ...
... The Cenozoic marine deposits in the area surrounding Puerto San Julián (Santa Cruz Province) were first described by Darwin (1846) and are composed mostly of volcanically derived and poorly indurated rocks including tuffaceous sandstones, siltstones, and massive tuff layers. The siltstones and sandstones are intercalated with calcareous, fossil-rich layers Casadío, 2005, 2006;Crawford et al., 2008;Malumián and Náñez, 2011;Parras et al., 2012;Cuitiño et al., 2018). ...
... The Monte León Formation (early Miocene) is about 180-200 m thick and consists of siltstone and fine-grained sandstone with a high proportion of pyroclastic material arising from contemporaneous volcanism in the Andean volcanic arc (Crawford et al., 2008). The Monte León Formation contains numerous accumulations of fossil invertebrates (del Río, 2004;Parras and Griffin, 2009;Casadio and Griffin, 2009;Parras et al., 2012;Cuitiño et al., 2018;Pineda-Salgado et al., 2018), and different depositional paleoenvironments were postulated for the unit, including a coastal environment (Echevarría, 2002) and hyposaline marsh and prodelta deposit (Olivera et al., 1994). ...
... The iron-oxide between cement crystals could be associated to bacterial activity in early fossilization stages, as stated by Maguire et al. (2016). The presence of volcanic glass in the early Miocene of Patagonia has been widely reported and has been associated with very well preserved infaunal taxa (Bertels, 1970;Di Paola and Marchese, 1973;Riggi, 1978;Casadio et al., 2005;Crawford et al., 2008, Cuitiño, 2011Parras et al., 2012;Maguire et al., 2016;Cuitiño et al., 2018). Also, high content of volcanic ash has been considered an important factor in fossil preservation, together with high sedimentation rates and poor sediment reworking (Rodríguez et al., 2008;Cuitiño, 2011;Maguire et al., 2016). ...
A single 27 m² spatangoid-dominated bed yielding 65 specimens from the Punta Entrada Member of the Monte León Formation was studied. Most of the fossils were preserved oral side down, with clusters of spines attached to the tests, showing no evidence of preburial transport. The deposit is interpreted as the result of sedimentation in a subtidal environment coeval with strong and continuous explosive volcanic activity, indicated by the significant amount of volcanic ash within the sediment. Echinoids assigned to Brisaster aff. B. iheringi De Loriol, 1902 colonized a distal part of the subtidal environment dominated by large-scale migrant bedforms. During dormant periods, it was characterized by low energy and low sedimentation rate, allowing colonization by several groups of infaunal organisms. Upon reactivation of sediment migration, a high sedimentary influx trapped the echinoids and prevented them from escaping.
... America was flooded by the shallow ''Entrerriense'' sea (Martínez and del Río, 2002;Marengo, 2015;Cuitiño et al., 2017;del Río et al., 2018). A southern branch of this "Entrerriense" sea occupied what is now the Península Valdés and the surrounding area of the Puerto Madryn city (Chubut Province), in northeastern Patagonia (Fig. 1). ...
... A southern branch of this "Entrerriense" sea occupied what is now the Península Valdés and the surrounding area of the Puerto Madryn city (Chubut Province), in northeastern Patagonia (Fig. 1). In this region, the late Miocene marine deposits are represented by the Puerto Madryn Formation (Haller, 1979), which is composed of heterolithic and cross-bedded sandstones, muddy sandstones, and sandy mudstones, interbedded with white tuffs and distinctive shell beds, reaching a maximum exposed thickness of 80 m (Haller et al., 2001).This unit preserves one of the best late Miocene fossil record of southern South America, and is characterised by highly diversified and abundant macrofossil content, dominated by marine invertebrates, predominantly molluscs (del Río, 1990;del Río, 2002, 2008;Casadío et al., 2005; among others), pinnipeds (Cozzuol, 2001), cetaceans (Cione et al., 2011;Buono et al., 2016;Cuitiño et al., 2017), marine fishes and birds (Riva Rossi et al., 2000;Acosta Hospitaleche et al., 2007) as well as continental mammals, birds and fishes (Dozo et al., 2010;Góis et al., 2013). Micropalaeontological studies are less abundant, including foraminifers (Caramés et al., 2004;Marengo, 2015) and palynomorphs (Palazzesi and Barreda, 2004;Palazzesi et al., 2014;Fuentes et al., 2016). ...
... The stratigraphic analysis of shell-beds allowed del to subdivide the unit in three phases, which from base to top are the Transgressive Phase, the Maximum Highstand Phase and the Regressive Phase. This scheme was held with little modifications in several other studies (e.g., Scasso et al., 2015;Cuitiño et al., 2017). Fossil rich, highly bioturbated beds are usually found at the Transgressive Phase and at the Maximum Highstand (Flooding) ...
The present work documents the stratigraphic distribution of dinoflagellate cysts from the upper part (60–585 m) of the YPF.Ch. PV. es-1 borehole, Península Valdés, Argentina. The assemblages exhibit a relatively moderate to low diversity. Most samples are characterized by frequent to abundant taxa of
the order Gonyaulacales, such as Spiniferites/Achomosphaera spp., Reticulatosphaera actinocoronata, Operculodinium centrocarpum, and Melitasphaeridium choanophorum. Furthermore, a continuous succession of Early Miocene–Late Miocene diagnostic dinoflagellate cyst events was recorded for the first time from the Península Valdés region. Eight diagnostic events of highest occurrences (HOs) of dinoflagellate cyst taxa are identified. These bioevents allowed a subdivision of the sedimentary succession into two well-defined stratigraphic sections: Early to Middle Miocene (Burdigalian–Langhian/probably
Serravalian, 430/425–330/325 m) based on the HOs of Emmetrocysta urnaformis, Cannosphaeropsis quattrocchiae, Cousteaudinium auybriae, and Cleistosphaeridium ancyreum, and Late Miocene (Tortonian–Messinian, between 175–170 and 80/85 m) based on the HOs of Labyrinthodinium truncatum subsp. truncatum, Operculodinium piaseckii, and Reticulatosphaera actinocoronata. The ranges of these taxa are compared with well-documented information on Neogene dinoflagellate cysts recorded from different sites across the North and South Atlantic Ocean and adjacent seas. In general, the dinoflagellate cyst assemblages, as well as the selected diagnostic taxa, exhibit a clear similarity to those of the Northern Hemisphere. The only exception is Hystrichokolpoma rigaudiae, which is asynchronous,
possibly indicating local paleoenvironmental conditions.
... Based on recent stratigraphic studies (e.g., Cuitiño et al., 2012Cuitiño et al., , 2017Parras and Cuitiño, 2018) we define the term Patagoniense as a succession of marine sediments displaying different thicknesses, sedimentary facies and stratigraphic architectures, accumulated at variable times and rates within the late Oligocene-early Miocene interval. They display a large geographic distribution throughout different basins of Patagonia. ...
... The Gaiman Formation is up to 130 m thick and consists of a succession of mudstones, fine tuffs, tuffaceous sandstones (Fig. 4C) and sparse shell beds, deposited in an inner shelf to shoreline environment (Scasso and Castro, 1999;Cuitiño et al., 2019b). Marine vertebrate remains are common, from which sharks, cetaceans and penguins are the most abundant (Cione et al., 2011;Cuitiño et al., 2017Cuitiño et al., , 2019b. A poorly preserved marine invertebrate fauna including large oysters and other bivalves, gastropods, echinoids, bryozoan, decapods, corals, and barnacles has also been mentioned (Cuitiño et al., 2019b). ...
Richly fossiliferous upper Oligocene to lower Miocene Patagoniense marine deposits constitute a conspicuous feature of the sedimentary record of most basins in Patagonia. Patagoniense meaning and subdivisions have been confusing, and correlation and elucidation of factors controlling sedimentation in a region as extensive as Patagonia are still highly debated. Our revision of the distribution, correlation, stratigraphic arrangement, and timing of deposition, allows redefining the Patagoniense as a succession of widely distributed marine sediments accumulated in Patagonia from ∼25 to 15 Ma, showing different timing of accumulation for each basin. It can also be conceived as a higher rank stratigraphic cycle of relative sea-level fluctuation, which comprises two medium rank stratigraphic cycles spanning 2–4 Myr each, in turn enclosing several lower rank cycles of less than 1 Myr. The late Oligocene (∼25-23 Ma) medium rank cycle shows deposits restricted mostly to the coastal area of Tierra del Fuego and Santa Cruz provinces in the Austral-Magallanes Basin, which respond to a combination of global sea-level fluctuations and flexural subsidence. The overlying early Miocene (∼22-15 Ma) medium rank cycle comprises sediments deposited over extensive areas of Patagonia with a maximum flooding at 20-19 Ma suggesting, in addition to tectonic subsidence in the Austral-Magallanes Basin, regional long-wavelength subsidence, and a global sea level component for this episode. The timing and thickness of the regressive part of this cycle show differences for each basin, suggesting the action of local sedimentary controls such as differential rates of sediment supply. Further geochronological and stratigraphic studies are necessary, especially for the northern exposures, which will allow improving time-constrained paleogeographic reconstructions.
... The latter corresponds to an informal unit also known as Patagoniense, rooted in the literature since the nineteenth century (Ameghino, 1906;Frenguelli, 1935;Simpson, 1935;Feruglio, 1949). Currently it comprises several lithostratigraphic units in Patagonia, ranging in age from the late Oligocene to the early Miocene (Cuitiño et al., 2017). These units were all deposited in shallow marine to estuarine environments, during a major marine transgression that flooded a large part of Patagonia (Scasso & Castro, 1999;Malumián & Náñez, 2011;Cuitiño et al., 2017). ...
... Currently it comprises several lithostratigraphic units in Patagonia, ranging in age from the late Oligocene to the early Miocene (Cuitiño et al., 2017). These units were all deposited in shallow marine to estuarine environments, during a major marine transgression that flooded a large part of Patagonia (Scasso & Castro, 1999;Malumián & Náñez, 2011;Cuitiño et al., 2017). The Patagoniense beds that crop out in the Lower Valley of the Chubut River and along the coastal cliffs of eastern Chubut Province were assigned to the Gaiman Formation (Mendía & Bayarsky, 1981). ...
Balaenidae (right and bowhead whales) are a key group in understanding baleen whale evolution, because they are the oldest surviving lineage of crown Mysticeti, with a fossil record that dates back ∼20 million years. However, this record is mostly Pliocene and younger, with most of the Miocene history of the clade remaining practically unknown. The earliest recognized balaenid is the early Miocene Morenocetus parvus Cabrera, 1926 from Argentina. M. parvus was originally briefly described from two incomplete crania, a mandible and some cervical vertebrae collected from the lower Miocene Gaiman Formation of Patagonia. Since then it has not been revised, thus remaining a frequently cited yet enigmatic fossil cetacean with great potential for shedding light on the early history of crown Mysticeti. Here we provide a detailed morphological description of this taxon and revisit its phylogenetic position. The phylogenetic analysis recovered the middle Miocene Peripolocetus as the earliest diverging balaenid, and Morenocetus as the sister taxon of all other balaenids. The analysis of cranial and periotic morphology of Morenocetus suggest that some of the specialized morphological traits of modern balaenids were acquired by the early Miocene and have remained essentially unchanged up to the present. Throughout balaenid evolution, morphological changes in skull arching and ventral displacement of the orbits appear to be coupled and functionally linked to mitigating a reduction of the field of vision. The body length of Morenocetus and other extinct balaenids was estimated and the evolution of body size in Balaenidae was reconstructed. Optimization of body length on our phylogeny of Balaenidae suggests that the primitive condition was a relatively small body length represented by Morenocetus, and that gigantism has been acquired independently at least twice (in Balaena mysticetus and Eubalaena spp.), with the earliest occurrence of this trait in the late Miocene–early Pliocene as represented by Eubalaena shinshuensis.
... The GF was deposited as a consequence of a regional transgression that flooded a large area of Patagonia, including the studied area, informally known as the Patagoniense transgression (Parras and Cuitiño 2021). The GF consists of a succession of bioturbated and tuffaceous mudstones and sandstones, and interspersed shellbeds, deposited in a marine inner shelf to shoreline paleoenvironment (Scasso and Castro 1999;Cuitiño et al. 2017;2019 and references therein). Important localities where the GF is well exposed (i.e. ...
... Evidence from extinct fishes, penguins (Cione et al. 2011), cetaceans Viglino et al. 2018a, b;Paolucci et al. 2020) and a palynological assemblage recovered from the study area (Palazzesi et al. 2006) also indicates a lower Miocene age. The minimum age is constrained by the overlying late Miocene Puerto Madryn Formation (Scasso & Castro 1999;Cuitiño et al. 2017). ...
Platanistoidea remains one of the most evolutionarily intriguing lineages of toothed whales (Odontoceti). The clade comprises mostly extinct species from the late Oligocene–early Miocene onward and a single extant riverine genus (Platanista). There is an ongoing debate as to the membership of Platanistoidea and the causes of their near extinction. In Patagonia (Argentina), the most abundant platanistoid recorded in the lower Miocene Gaiman Formation is Notocetus vanbenedeni, first described by Moreno in 1892 based on two individuals. The goal of the present contribution is to conduct an updated anatomical, palaeobiological and phylogenetic analyses of Notocetus vanbenedeni and hence contribute to an understanding of the evolutionary history of the Platanistoidea. Our analyses, including at least 26 individuals (12 undescribed), show that Notocetus vanbenedeni is a valid platanistoid taxon, recovered as part of a new clade. Among its most outstanding features, this taxon has an elevated dorsal tubercular supraorbital crest formed mainly by the frontal, the precursor of the pneumatized crest of the extant Platanista. Notocetus vanbenedeni also shows initial stages of the plesiomorphic bony connection between the earbones and skull as in Platanista, although the functional implications for hearing remain elusive. The nasal sac system, pterygoid sinus system and morphology of the earbones suggest that this species was able to hear high-frequency sounds and echolocate underwater, similar to extant odontocetes. Thus, Notocetus vanbenedeni presents a mosaic of features that suggest an intermediate platanistoid morphotype. Anatomical differences and phylogenetic analyses suggest that Peruvian specimens could not be referred to this species. The feeding apparatus of Notocetus vanbenedeni makes it the only combination suction-feeder recorded in the early Miocene of Patagonia and among the smallest odontocetes. Finally, the abundant records of Notocetus vanbenedeni in an inner shelf environment with freshwater influence suggest a possible early preference for such protected habitats.
... Turtles in this member proceed from a grayish tuffaceous siltstone the lowermost part, a bed containing abundant fossil mammals (Fleagle & Bown, 1983). The Gaiman and Puerto Madryn formations are constituted by tuffs, sandstones, mudstones, and coquines, deposited within inner shelf (Gaiman and Puerto Madryn formations) to estuarine, tidal or lagoonal (Puerto Madryn Formation) systems (Scasso & del Río, 1987;Scasso & Castro, 1999;Scasso & Bellosi, 2004;dozo et al., 2010;Scasso et al., 2012b;Cuitiño et al., 2017;. Specimens from the Gaiman Formation proceeds from a terrestrial bed in the lower section, in the transition to the underlying Sarmiento Formation (Trelew Member) (Simpson, 1942;de la Fuente & Vucetich, 1998). ...
In this work we focus on the fossil record of turtles and tortoises from the Chubut Province, in Patagonia, Argentina. This record is the richest, most diverse, the longest and continuous in the country and one of the most important in the continent. In this work, we present and study new fossils from all known clades of turtles from the province, coming from targeted field campaigns, as well as from past investigations, placed in a comprehensive and detailed chronostratigraphic context. In Chubut, more than 241 occurrences of turtles from at least 223 collection points are known, spanning from the Toarcian (Jurassic) to the Tortonian (Miocene). we manage to fill some of the gaps in the fossil record, complete the anatomical knowledge of many taxa, explore new geographical areas, and present some important highlights. Among these, the record of the oldest pan-chelid turtles indicates the significant potential of the sedimentary deposits of Chubut. Furthermore, we discuss the changes in the diversity and faunal turnovers of the various turtle clades in this region during the last 180 Ma and across important events during the Cretaceous/Paleocene and Oligocene/Miocene boundaries.
... It is formed by 50 meters of sandstones, tuffaceous sandstones, and limestones, with cross-bedded stratification and ondulites.These deposits correspond to a closed marine environment dominated by tidal regimes in normal marine conditions. Fossil vertebrate remains are wellpreserved and usually disarticulated, and they are mainly cetacean fragments, such as balaenids, neobalaenines, balaenopterids, and ziphiids(Cuitiño et al., 2017). Fossil invertebrates include significant accumulations of the echinoid Monophoraster darwini(Desor, 1847)Geographic and stratigraphic provenance of MACN-Pv 20064. ...
... This fact enhances C. quattrocchiae as key taxa for regional correlation of the Burdigalian to earliest Langhian maximum flooding interval in the subsurface across the Valdés and Colorado basins (Fig. 4). Besides, dinocyst assemblages from the maximum flooding interval at the PV borehole suggest correlation with the lower Miocene marine strata along the east coast of Patagonia, i.e. the ´Patagoniense´ successions of the Chenque Formation in the Golfo San Jorge Basin (Palamarczuk and Barreda, 1998;Barreda and Palamarczuk 2000a) and the Monte León Formation in the Austral Basin (Parras et al., 2012;2020;Barreda and Palamarczuk 2000b) and probably the Gaiman Formation west of the PV borehole (Cuitiño et al., 2017;. ...
Key information for regional biostratigraphic, climatic and environmental reconstructions for the Miocene of the southwestern Atlantic margin can be obtained by qualitative and quantitative palynological analysis at the onshore YPF-CH-PV.es-1 borehole (PV borehole) in the Valdés Basin, combined with previously documented organic-walled dinoflagellate cyst data from the Colorado Basin and well-dated outcropping sections on the east coast of Patagonia. A sequence of eleven significant dinocyst bioevents (highest occurrence, HO; highest common occurrence, HCOs) is recognized across the Valdés and Colorado basins. The bioevents occur in the same stratigraphic order and seem to be synchronous across both basins. From the oldest to the youngest, these are: HO of Emmetrocysta urnaformis, HO of Cannosphaeropsis quattrocchiae, HCO and HO of Hystrichokolpoma rigaudiae, HO of Cousteaudinium auybriae, HCO and HO of Dapsilidinium pseudocolligerum, HO of Cleistosphaeridium ancyreum, HO of Labyrinthodinium truncatum, HO of Operculodinium piaseckii and HO of Reticulatosphaera actinocoronata. The presumed climatically-driven extinctions of Dapsilidinum pseudocolligerum and Hystrichokolpoma rigaudiae around the Burdigalian to earliest Langhian, may be linked to global cooling and the re-establishments of the Antarctic ice-sheets since ∼14 Ma. Two maximum flooding episodes, characterized by warm, outer (distal) neritic environmental conditions were identified at the PV borehole, presumably related to glacio-eustatic sea level rise. The older occurred in the Burdigalian – earliest Langhian and the younger, in the Tortonian. The latter maximum flooding is followed by environmental and/or climatically-driven change, implying abrupt shifting from neritic to nearshore conditions, the extinction of the warm-water taxa, and dinocysts being largely replaced by acritarchs.
... Prior to this Neogene uplift, the Andean and extra-Andean areas of Patagonia were largely covered by marine deposits with Pacific and Atlantic affinities, respectively (e.g., Malumián and Yañez, 2011;Encinas et al., 2013;Bechis et al., 2014;Encinas et al., 2016a;Cuitiño et al., 2017), in some areas possibly with transient oceanic connection (see below). These Eocene-early Miocene marine strata ( Fig.1) represent the climax and final stage of an extensional episode that started during the early Cenozoic (Aragón et al., 2011;Hervé et al., 2017;Encinas et al., 2019), following Lower and Upper Cretaceous orogenic phases (Gianni et al., 2018 and references therein). ...
Previously undated low-grade metamorphic rocks from the Puerto Cisnes-Queulat area (44°30’ S) contain detrital zircons of mid-Oligocene age (ca. 28 Ma). Their outcrops represent the easternmost occurrence of the late Oligocene to early Miocene marine volcano-sedimentary Traiguén Formation; previous correlation with the Paleozoic metamorphic basement of this sector of the North Patagonian Andes is thus refuted. A similar age and provenance were obtained for a paraconglomerate bed of the La Junta Formation ca. 80 km to the north, which is thought to represent a high-energy lateral facies variation of the Traiguén Formation. Miocene plutonic rocks of the North Patagonian Batholith intruded these metasedimentary rocks, generating a contact metamorphic aureole that reaches biotite grade and overprints a previous metamorphic fabric probably formed during closure of the Traiguén Basin. Similar young ages for metamorphic rocks located immediately west of the Liquiñe-Ofqui Fault Zone 300 km north, near Ayacara, suggest a regional pattern of earliest Neogene metamorphism and rapid exhumation in this segment of the Patagonian Andes.
... The Gaiman Formation is composed of shallow marine sediments that are well exposed at Bryn Gwyn. The depositional settings, age, and fossil cetacean content of this unit are discussed in Cuitiño et al. (2017Cuitiño et al. ( , 2019. ...
Sperm whales (Physeteroidea) include today only two genera of morphologically disparate odontocetes: the largest
toothed whale known (Physeter macrocephalus) and small sized forms (Kogia spp.). In contrast, their fossil record indicates
a high diversity for the group during the Miocene, with over 20 species recognized. Miocene marine sediments from
Patagonia (Argentina) record this diversity, including at least five species. Among them, Preaulophyseter gualichensis,
from the Miocene of Gran Bajo del Gualicho Formation, has been one of the most enigmatic. Despite the fragmentary
nature of the type and referred materials (isolated teeth and periotics), which casts some doubts on its validity, this species
has not been revised since its original description. In this contribution, we re-describe the materials referred to P. gualichensis,
revise the taxonomic status of the species and evaluate the phylogenetic signal of ear bones among Physeteroidea.
Our results indicate that the physeteroid tympano-periotic complex morphology is poorly diagnostic at the species level.
Intraspecific variation (including ontogeny and sexual dimorphism) and/or taphonomic processes cannot be ruled out as
the causes of the minor differences observed among specimens. We suggest that sperm whale tympano-periotics
retain
many plesiomorphic characters and are diagnostic only between kogiids and non-kogiid physeteroids. Based on the fragmentary
and isolated state of the studied specimens, and the lack of diagnostic characters in both teeth and periotics, we
consider P. gualichensis as nomen dubium and we re-assign the referred specimens as Physeteroidea indet. A conservative
morphology of the tympano-periotic and, to a lesser extent, the nasal complex in sperm whales, might result from the
morpho-functional constraints imposed by a highly specialized but successful echolocation system.
... Prior to this Neogene uplift, the Andean and extra-Andean areas of Patagonia were largely covered by marine deposits with Pacific and Atlantic affinities, respectively (e.g., Malumián and Yañez, 2011;Encinas et al., 2013;Bechis et al., 2014;Encinas et al., 2016a;Cuitiño et al., 2017), in some areas possibly with transient oceanic connection (see below). These Eocene-early Miocene marine strata ( Fig.1) represent the climax and final stage of an extensional episode that started during the early Cenozoic (Aragón et al., 2011;Hervé et al., 2017;Encinas et al., 2019), following Lower and Upper Cretaceous orogenic phases (Gianni et al., 2018 and references therein). ...
Previously undated low-grade metamorphic rocks from the Puerto Cisnes-Queulat area (44°30'S) contain detrital zircons of mid-Oligocene age (c. 28 Ma). Their outcrops represent the easternmost occurrence of the late Oligocene to early Miocene marine volcano-sedimentary Traiguén Formation; previous correlation with the Paleozoic metamorphic basement of this sector of the North Patagonian Andes is thus refuted. A similar age and provenance were obtained for a paraconglomerate bed of the La Junta Formation c. 80 km to the north, which is thought to represent a high-energy lateral facies variation of the Traiguén Formation. Miocene plutonic rocks of the North Patagonian Batholith intruded these metasedimentary rocks, generating a contact metamorphic aureole that reaches biotite grade and overprints a previous metamorphic fabric probably formed during closure of the Traiguén Basin. Similar young ages for metamorphic rocks located immediately west of the Liquiñe-Ofqui Fault Zone 300 km north, near Ayacara, suggest a regional pattern of earliest Neogene metamorphism and rapid exhumation in this segment of the Patagonian Andes. I N P R E S S 2 Resumen Rocas metamórficas de bajo grado presentes en el área Puerto Cisnes-Queulat (44°30'S) contienen circones detríticos de edad Oligoceno medio (c. 28 Ma). Estos afloramientos corresponden a la ocurrencia más oriental de las rocas volcano-sedimentarias de la Formación Traiguén, de edad Oligoceno tardío a Mioceno temprano; correlaciones previas con el basamento metamórfico de edad Paleozoica de esta porción de los Andes Norpatagónicos son descartadas. Una edad máxima y fuentes de procedencia similares se obtuvieron en un paraconglomerado de la Formación La Junta, unos 80 km al norte, la cual se interpreta como una variación lateral de alta energía de la Formación Traiguén. Rocas plutónicas del Mioceno pertenecientes al Batolito Norpatagónico intruyen a las rocas metasedimentarias, generando una aureola de contacto que alcanza el grado metamórfico de la biotita, y se sobrepone a una fábrica metamórfica anterior probablemente relacionada con el tectonismo producto del cierre de la cuenca Traiguén. Edades Cenozoicas similares han sido obtenidas para rocas metamórficas ubicadas inmediatamente al oeste de la Zona de Falla Liquiñe-Ofqui 300 km al norte, cerca de Ayacara, lo cual sugiere un patrón regional de metamorfismo y exhumación en una rápida sucesión durante el Neógeno más temprano en este segmento de los Andes Patagónicos. Palabras claves: Formación Traiguén, Zona de Falla Liquiñe-Ofqui.
... Both units are composed of medium to fine sandstones and limestones assigned to a marine transgression. Both were deposited in a marine and littoral environment with an important input of fine pyroclastic materials from the west (Cuitiño et al., 2017;Haller et al., 2005). They also present a significant paleontological content of marine fauna. ...
Bunicontro, M.P.; Marcomini, S.C., and López, R.A., 2020. Coastal morphology and human intervention in Golfo Nuevo, Patagonia Argentina. Journal of Coastal Research, 36(4), 780–794. Coconut Creek (Florida), ISSN 0749-0208.The Patagonian coastal zone is a complex and dynamic macrotidal environment that is sparsely urbanized, except locally where large cities are located. This human occupation has affected the natural beach dynamics and induced drastic coastal changes in the past 40 years that demand a redirection of initiatives to provide a basis for management efforts. This study analyzes the coastal morphology and beach characteristics of Golfo Nuevo (Chubut, Argentina) for modelling coastal behaviour through field measurements along 17 beach profiles. Beaches were classified into four types according to their sediment grain size, morphology, and morphometric parameters (beach width and gradient). Also, the coast was divided into five categories according to the coastline morphologies and environmental quality: (1) littoral pediments, (2) cliff-top dunes and aeolian ramps, (3) active cliffs, (4) beach ridge terraces, and (5) dunes. Additionally, different human interventions were analyzed to determine how they have affected the natural coastal equilibrium. The coast was divided into low, moderate, and high levels of intervention according to the status of the landscape modification. The most shocking activities were identified as mining (gravel and sand extraction), coastal armouring with hard defences, and urban building. Indeed, the most affected and vulnerable coastal areas have been beach ridge terraces and coastal dunes. It was determined that the coastal extension affected by these human activities reaches at least 37% of the study zone, increasing beach and coastal erosion susceptibility. The coastal classification and the evaluation of human intervention were combined and used to perform an accurate zoning map of the coastal environment. This map represents an essential tool for decision makers of Puerto Madryn city, showing clearly the most vulnerable places where coastal planning strategies urgently need to be applied for a sustainable use of resources.
... The fossil-bearing marine deposits of the Gaiman Formation are exposed in the northeast of the Chubut Province (Argentina), around the localities of Trelew, Gaiman, Rawson and Cañadón Iglesias (Tonni, 1979;Scasso and Castro, 1999;Noriega et al., 2008;Cione et al., 2010). Its sediments are the result of the older of the two major marine transgressions that covered part of Patagonia during the Miocene (Cuitiño et al., 2017;Fuentes et al., 2019). This for- (Scasso and Castro, 1999). ...
... The eastern Atlantic coast of South America has promising outcrops to expand the Miocene record of platanistoids, as it possesses one of the few early Miocene marine beds globally (i.e., Gaiman Formation; Scasso and Castro 1999;Cuitiño et al. 2017). For this epoch, the Gaiman Formation holds a remarkably rich and well-preserved assemblage of cetaceans (e.g., Cuitiño et al. 2017 and references therein). ...
The contents of the superfamily Platanistoidea, an early-diverging lineage comprising extinct species and a single extant representative of South Asian river dolphin (Platanista gangetica), remain controversial. We describe here a partial skull and associated tympano-periotic bones identified as a new genus and species, Aondelphis talen gen. et sp. nov., collected in the lower levels of the Gaiman Formation (early Miocene), in Patagonia (Chubut Province, Argentina). Aondelphis is the first Patagonian platanistoid species named in almost a century. Phylogenetic analyses suggest Aondelphis talen gen. et sp. nov. and a taxon from New Zealand (cf. Papahu ZMT-73) are basal Platanistoidea sensu lato. Unambiguous synapomorphies related to the ear bones allowed us to determine its phylogenetic position. Aondelphis talen markedly differs from the other well-known early Miocene Patagonian platanistoid Notocetus, suggesting the coexistence of at least two different morphotypes that may have occupied different ecological niches at that time. The putative close relationship with a species from New Zealand indicates there was a rapid diversification and widespread distribution of the group in the Southern Hemisphere during the early Miocene. The description of new species and revision of historical records of Patagonian platanistoids can help shedding light on cetacean assemblages of the Patagonian sea during this epoch.
Abstract. Recent fieldwork on Neogene deposits of northern Chile led to the discovery of new material, including three new species of the echinoid genus Arbacia: Arbacia quyllur sp. nov. from the Miocene, Arbacia terraeignotae sp. nov., and Arbacia larraini sp. nov. from the Pliocene. In the Pleistocene, the new material includes the first fossil occurrence of the extant species Arbacia spatuligera and new specimens of the extant species Tetrapygyus niger. The specimens and new species described here reveal the significant past diversity of the genus Arbacia and increase our knowledge of the overall diversity of the genus in South America, showing an older origin (upper Miocene) and higher species richness of the genus Arbacia along the Chilean coasts than previously thought.
Key words. Paleobiogeography. Fossils. Echinoid. Arbacia. Chile.
Resumen. Recientes trabajos de campo en el Neógeno del norte de Chile han permitido descubrir nuevos materiales, entre ellos tres nuevas especies del género de equinoideo Arbacia: Arbacia quyllur sp. nov. (Mioceno), Arbacia terraeignotae sp. nov. y Arbacia larraini sp. nov. (Plioceno), pero también la primera aparición de Arbacia spatuligera y nuevo material de Tetrapygyus niger (Pleistoceno). Los especímenes y las nuevas especies aquí descritas revelan la diversidad pasada del género Arbacia. Estos descubrimientos muestran la existencia de una mayor riqueza de Arbacia a lo largo de las costas chilenas y un origen más antiguo del género en la costa del Pacífico Sureste (Mioceno superior).
Palabras clave. Paleobiogeografía. Fósiles. Equinoideo. Arbacia. Chile.
A right carpometacarpus (MLP 10-XII-11-1) from the early Miocene Gaiman Formation was collected in the fossiliferous locality Bryn Gwyn (Chubut Province, Argentina). After extensive comparisons with extinct and extant species, and geometric morphometric analyses, we concluded that it belongs to Procellariidae. It is supported by the presence of sulcus tendineus restricted to the distal half, a small crest belonging to the m. ulnometacarpalis dorsalis scar, notch and tubercle on the ventral rim of trochlea carpalis, a wide fovea carpalis caudalis not proximally delimited, a rounded, shallow, and proximo-cranial fossa supratrochlearis, and pneumatic foramina within the small fovea carpalis caudalis. The geometric morphometric analyses show clear similarities with Procellariidae, and locate MLP-10-XII-11-1 close to Procellaria aequinoctialis, Daption capense and Pterodroma incerta in the dorsal configuration, and to P. incerta and Macronectes giganteus in the ventral one. Also, the dorsal configuration is more conservative within families than the ventral one. Although this carpometacarpus does not present any exclusive character, the combination of characters found in the new fossil is unique, suggesting that MLP 10-XII-11-1 might represent a new genus and species. However, the proposal of a new species must wait until more complete specimens are found.
Lower Miocene outcrops from Patagonia (Gaiman Formation, Burdigalian) may reveal more clues for the yet unknown aspects for this period in the evolution of odontocetes. Here, we present the first toothless platanistoid dolphin from the lower Miocene of Patagonia, Dolgopolis kinchikafiforo, gen. et sp. nov. The specimen includes an incomplete skull, with no mandibles or earbones, but sufficiently different from other named odontocetes to propose a new genus and species. Phylogenetic analyses indicate it is a platanistoid of uncertain position within the group, and that it shares some homoplastic characters with physeteroids and ziphioids. Given the absence of defined alveoli and teeth and an inferred moderately short and wide rostrum, we interpreted this new species as most likely a capture suction feeder. Based on our phylogenetic hypothesis, the optimization of feeding strategies recovered raptorial feeding as the plesiomorphic method, and convergent evolution of capture suction feeders in at least four lineages. Platanistoids recorded all feeding strategies during the late Oligocene-early Miocene, although raptorial is the predominant method. This suggests a partitioning of the ecological niches in the early phases of platanistoid evolution, as well as a high diversification of feeding methods previously underestimated for this period. Thus, ecological adaptations have a strong evolutionary pressure in odontocete communities and should be further explored.
Sperm whales (Physeteroidea) are the basal-most surviving lineage of odontocetes, represented today by just three highly specialized, deep-diving suction feeders. By contrast, extinct sperm whales were relatively diverse, reflecting a major Miocene diversification into various suction feeding and macroraptorial forms. The beginnings of this diversification, however, remain poorly understood. The Atlantic coast of South America provides a crucial window into early physeteroid evolution and has yielded some of the oldest species known from cranial material, Idiorophus patagonicus and Diaphorocetus poucheti – both of which are in need of re-description and phylogenetic reappraisal. Here, we re-examine Diaphorocetus in detail and, in light of its complex taxonomic history, declare it a nomen protectum. Phylogenetically, the species forms part of a polytomy including ‘Aulophyseter’ rionegresis and the two crown lineages (Physeteridae and Kogiidae) and demonstrates that facial asymmetry and a clearly defined supracranial basin have characterized this lineage for at least 20 Ma. With a total body length of 3.5–4 m, Diaphorocetus is one of the smallest physeteroids yet known. Its cranial morphology hints at an intermediate raptorial/suction feeding strategy and it has a moderately developed spermaceti organ and junk.
Biofacies and taphonomic analysis has allowed for the reconstruction of the paleoenvironmental history of accumulation of a series of spectacular mollusk-dominated shell-concentrations from the Puerto Madryn Formation and the benthic assemblages that inhabited the Miocene sea in northern Patagonia, Argentina. An upward-shallowing from open mid-shelf to more restricted shoreface-foreshore environments has been recognized. Transgressive, Maximum Highstand and Regressive phases are recognized based on the integrated approach of assemblages and lithofacies arrangement. Eleven mollusk-dominated fossil assemblages were defined and grouped into Associations A,B, and C. Transgressive and Maximum Highstand phases preserve three main shell beds that record an upwards change from dynamic to complete bypassing conditions. These were deposited in tidal current-dominated mid- and inner-shelf environments and belong within Association A. The top bedding surface records the maximum depth attained by the sea. The Regressive Phase is characterized by three upward-deepening cycles comprised of foreshore-shoreface sandbar deposits containing Association C. Sandbars are capped by environmentally condensed shell-beds of Association B and record deposition from the shoreface (wavebreaking zone) to mid-shelf environments, all above stormwave base. Based on these fossil assemblages, seven benthic life associations can be identified. The deepest ones inhabited the mid-to-inner shelf and were represented by suspensionfeeders from gravel-substrata swept by strong tidal currents and by suspension-feeders from lower energy firm bottoms. Lower shoreface sandy bottoms, close to fairweather wave base and affected by weak tidal currents, were inhabited by epifaunal suspension-feeders, whereas sandy bottoms close to the fairweather wave-breaking zone were characterized by semi-infaunal deposit feeders and suspension feeders. The shallowest living assemblages inhabited intertidal and foreshore settings and were represented by soft-bottom infaunal suspension feeders, as well as by firm bottom, vagile carnivorous and suspension-feeding epifauna.
A new species of Ophioderma Müller and Troschel, 1842 is described. The new species is the first fossil one of the genus, and the third ophiuroid described for the Tertiary of South America. It is characterized by its large size, proximal dorsal arm plates arched, entire or irregularly fragmented in two or three parts and lateral arm plates with four or five short, flat spines of similar length with a finger-like outline.
The age and stratigraphic subdivisions for the late Oligocene-Miocene, marine deposits of Patagonia (Patagoniense succession) have been largely debated. Most studies for the Comodoro Rivadavia region were focused on its biostratigraphy and stratigraphic relations with the underlying and overlying mammal-bearing terrestrial strata. We report here thirteen new 86 Sr/ 87 Sr ages obtained from well-preserved oyster valves of the Chenque Formation in the classical Patagoniense outcrops around the city of Comodoro Rivadavia (Golfo San Jorge Basin, Argentina). According to these ages, the deposition of the unit in the region occurred between 19.69 and 15.37 Ma (Burdigalian-early Langhian). A lower interval of normal sedimentation rate (Sequences 1 and 2) and an upper interval of high sedimentation rate (Sequence 3) are defined according to these new ages of the Chenque Formation. Subsequently, the depositional age of the Chenque Formation is compared with other well-dated marine successions of southern Patagonia located within the Austral Basin. This analysis suggests that the Austral and Golfo San Jorge basins were flooded by the Atlantic sea at about the same time (~21-20 Ma), inundating what was before a vast continental region of southern Patagonia. A renewed phase of continentalization occurred at about 18 Ma in the Austral Basin and at about 15 Ma in the study region of the Golfo San Jorge Basin. This 3 my difference combined with the elevated sedimentation rate estimated for the upper part of the study interval, suggest that the Golfo San Jorge Basin may have locally experienced relatively high subsidence rates during the early Miocene, allowing prolonged marine sedimentation in the Comodoro Rivadavia area. Consequently, the accumulation of the terrestrial deposits assigned to the Santa Cruz Formation started at about 15 Ma in the study region, later than in other localities of southern Patagonia. This results clearly indicate a remarkable interdigitation between the Santa Cruz and Chenque formations in a west-east transect across central Patagonia.
La Cuenca de Gastre ubicada a centenares de kilómetros del margen de subducción, constituye una de las mayores cuencas intermontanas desarrolladas dentro del antepaís fragmentado patagónico. Su origen en el Mioceno medio se encuentra estrechamentevinculado a estructuras contraccionales las cuales exhumaron bloques de basamento pre-mioceno y configuraron el
espacio necesario para la acumulación y preservación de un registro sedimentario continuo desde el Mioceno a la actualidad.El presente estudio analiza el relleno neógeno de la Cuenca de Gastre evaluando la relación entre los principales factores que intervinieron en la evolución dinámica de la cuenca y el registro estratigráfico/sedimentario. Sobre la base de un análisis estratigráfico,sedimentológico y estructural se pudo dividir el relleno en etapas pretectónica, sintectónica y postectónica, acotadastemporalmente con edades preexistentes. La etapa pretectónica (Mioceno inferior tardío) se corresponde con un evento de subsidencia regional asociado a la flexión del antepaís, con influencia de volcanismo explosivo en ambientes sedimentarios de bajo gradiente. La etapa sintectónica (Mioceno medio) coincide con la estructuración de la Cuenca de Gastre donde se conformaron depocentros aislados en los cuales se desarrollaron sistemas lacustres efímeros. La etapa postectónica (Mioceno medio-Plioceno) abarca el periodo depositacional caracterizado por grandes lagos bajo influencia de volcanismo explosivo hasta el desarrollo de ambientes aluviales y sistemas fluviales entrelazados. Esta última etapa marcó la merma abrupta del aporte volcaniclástico que caracterizó a las sucesiones miocenas del ámbito nordpatagónico y el pasaje del óptimo climático mioceno al periodo de aridización, producto del levantamiento de los andes.
La Cuenca de Gastre ubicada a centenares de kilómetros del margen de subducción, constituye una de las mayores cuencas intermontanas desarrolladas dentro del antepaís fragmentado patagónico. Su origen en el Mioceno medio se encuentra estre-chamente vinculado a estructuras contraccionales las cuales exhumaron bloques de basamento pre-mioceno y configuraron el espacio necesario para la acumulación y preservación de un registro sedimentario continuo desde el Mioceno a la actualidad. El presente estudio analiza el relleno neógeno de la Cuenca de Gastre evaluando la relación entre los principales factores que intervinieron en la evolución dinámica de la cuenca y el registro estratigráfico/sedimentario. Sobre la base de un análisis estra-tigráfico, sedimentológico y estructural se pudo dividir el relleno en etapas pretectónica, sintectónica y postectónica, acotadas temporalmente con edades preexistentes. La etapa pretectónica (Mioceno inferior tardío) se corresponde con un evento de subsidencia regional asociado a la flexión del antepaís, con influencia de volcanismo explosivo en ambientes sedimentarios de bajo gradiente. La etapa sintectónica (Mioceno medio) coincide con la estructuración de la Cuenca de Gastre donde se confor-maron depocentros aislados en los cuales se desarrollaron sistemas lacustres efímeros. La etapa postectónica (Mioceno medio-Plioceno) abarca el periodo depositacional caracterizado por grandes lagos bajo influencia de volcanismo explosivo hasta el desarrollo de ambientes aluviales y sistemas fluviales entrelazados. Esta última etapa marcó la merma abrupta del aporte vol-caniclástico que caracterizó a las sucesiones miocenas del ámbito nordpatagónico y el pasaje del óptimo climático mioceno al periodo de aridización, producto del levantamiento de los andes. palabras clave: Cuenca intermontana, intraplaca, Mioceno, Formación Collón Curá, factores alocíclicos aBstRact Intermontane infill in the Patagonian broken foreland: Neogene evolution of the Gastre Basin The Gastre Basin is one of the largest intermontane basins of the Patagonian Broken Foreland. It is oblique to the Andean chain and located more than 550 km east of the Andean trench. It was originated by reverse faulting and inversion of pre-existing normal faults during the Middle-Miocene, allowing the preservation of a continuous sedimentary record up to the present. Stratigraphic, sedimentologic and structural observations indicate a pre-tectonic, syn-tectonic and post-tectonic evolution stage. The pre-tectonic stage (late Lower Miocene) was related to a combination of a flexural subsidence event in the foreland in response to the tectonic activity in the fold and thrust belts, and the influence of explosive volcanism over low-gradient sedimentary environments. The syn-tectonic stage (Middle Miocene,) is marked by the contractional deformation event in which the Gastre Basin was structurally configured. During this stage, basin compartmentalization associated with shallow lacustrine systems occurred. The post-tectonic stage (Middle Miocene-Pliocene) involves the post-deformational deposits characterized by deep lacustrine systems under explosive volcanism influence as well as the alluvial and braided fluvial system. During this stage an abrupt decreasing of the volcaniclastic supply, which characterized the Miocene Northpatagonian successions, occurred. This was combined with a major climatic change developed in the Middle Miocene that corresponds with the change from the optimal climate to the aridity period in response to the Andean uplift.
Early Miocene shallow marine deposits in the region of Lago Posadas-Meseta Belgrano (Argentina)
represent part of the “Patagoniense” transgression, an Atlantic marine incursion that flooded large part of Patagonia, including the Austral (foreland) Basin (southern Patagonia). These deposits, referred as El Chacay (Argentina) or Guadal (Chile) formations, and the transition to the overlying Santa Cruz Formation were divided into six facies: subtidal sand-bars, shallow marine sandy deposits, muddy shelf deposits, estuarine complex deposits, fluvial channels and fluvial floodplains. These are arranged in a general transgressive-regressive cycle, subdivided into two stratigraphic sequences, separated by a major erosional surface. 87Sr/86Sr ages from shell carbonate in eight oysters yielded an age range of 20.3 to
18.1 Ma for these “Patagoniense” deposits. Correlation with other dated “Patagoniense” sections in southern Patagonia, like those at Lago Argentino or Comodoro Rivadavia, indicates that they belong to a single transgression that flooded several Patagonian basins approximately at the same time. Eustasy, flexural subsidence created by tectonic loading in the adjacent fold-and-thrust belt, and basin floor paleo-topography controlled the duration of the depositional event and the sedimentation style of these shallow marine deposits.
A diverse and well preserved palynological assemblage is described for the first time from Puerto Madryn Formation, Puerto Pirámide outcrops, Valdés Peninsula. A Middle Miocene or Late Miocene age was suggested based on fossil remains or radiometric records. The recovered palynologic assemblage has palynomorphs of marine and continental origins, present in similar frequencies. Freshwater algae are abundant. The spore-pollen assemblage is dominated by herbaceous and shrubby elements, which suggest a halophytic and xerophytic vegetation. Chenopodiaceae [Chenopodipollis chenopodiaceoides (Martin) Truswell], Ephedraceae (Equisetosporites spp.), Convolvulaceae (Tricolpites trioblatus Mildenhall and Pocknall), and Asteraceae (Tubulifloridites spp.) are the dominant families, with subordinate Poaceae (Graminidites sp.), Malvaceae (Baumannipollis spp.) and Anacardiaceae (Striatricolporites spp.). The presence of Restionaceae (Milfordia sp.), Sparganiaceae/Typhaceae (Sparganiaceaepollenites barungensis Harris), Azollaceae (Azolla sp.) and Cyperaceae (Cyperaceaepollis neogenicus Krutzsch) indicates the development of a hydrophytic community. Arboreal components are poorly represented by Podocarpaceae, Araucariaceae and Nothofagaceae, bryophytes and pteridophytes are also very scarce. The palynological assemblage suggests a shallow coastal marine environment, with high continental input. The spore-pollen assemblage indicates salt marsh vegetation with littoral ponds of brackish to fresh water setting. A Late Miocene age is indicated by the presence of the key species Tubulifloridites pleistocenicus Martin and T. simplis Martin. No evidence of warm to warm-temperate climatic conditions were recognized from the palynological assemblage, however dry environments would have prevailed as was pointed out by the dominance of shrubby and xerophytic elements.
The capybaras (Hydrochoeridae) are outstanding rodents for their large size and euhypsodont and multilaminated cheek teeth. Although today they are represented by a single species, it was generally thought that their past diversity was much higher, especially during the late Miocene-early Pliocene. Such diversity is here analyzed taking into account the ontogenetic variation of the p4-m3 in different populations. Numerous isolated teeth of different size found in the upper levels of the Puerto Madryn Formation (late Miocene, Peninsula Valdés, Argentina) were interpreted as members of an ontogenetic series of a new species here described, Cardiatherium patagonicum. They provided clues to evaluate ontogenetic variation and a new framework to analyze the family diversity. In this context, it is proposed that multiple species described from the Ituzaingó Formation (late Miocene, Entre Ríos, Argentina) based on lower teeth, may actually represent specimens of different stages of the ontogenetic trajectory of a single species. Likewise, we found that several nominal taxa from other localities were based on juvenile specimens. According to these results, the diversity of the Hydrochoeridae during the late Miocene and early Pliocene was drastically reduced. The validity of the subfamily Cardiatheriinae is debated. Finally, it is suggested that the whole family should be revised taking into account the ontogenetic variation.
The lower Miocene Chenque Formation of Patagonia contains superbly preserved and diverse ichnofaunas, including the ichnogenera Asterosoma, Balanoglossites, Chondrites, Gastrochaenolites, Gyrolithes, Helicodromites, Macaronichnus, Nereites, Ophiomorpha, Palaeophycus, Phycosiphon, Planolites, Protovirgularia, Rhizocorallium, Rosselia, Schaubcylindrichnus, Scolicia, Siphonichnus, Skolithos, Spongeliomorpha, Taenidium, Teichichnus, and Thalassinoides. Wave-influenced open-marine deposits are characterized by intense bioturbation, complex tiering structures and a very high diversity. Restricted, brackish-water, tide-dominated deposits display lesser degrees of bioturbation, less complex tiering structures and lower ichnodiversity. Both marginal- and open-marine deposits are commonly punctuated by discontinuity surfaces delineated by firmground ichnofaunas. The complex tiering structure of open marine ichnofaunas shows the development of a finely partitioned infaunal niche and an increment in bioturbation by the Neogene, which is consistent with trends revealed by body fossils. However, further expansion of the Cenozoic ichnologic database is necessary in order to evaluate the role of evolutionary and latitudinal controls.
Fossil capybaras are morphologically extremely varied, but previous studies have disagreed on whether this diversity reflects intraspecific variation or the existence of multiple species. Here, we review the capybaras from the classic Argentinian Late Miocene localities of Parana River cliffs ("conglomerado osifero" of the Ituzaingo Formation, Entre Rios), and Chillhue and Guatrache shallow lakes (Cerro Azul Formation, La Pampa), and perform a morphometric analysis of their upper cheek teeth and the posterior portion of the rostrum. Our results confirm that all of the specimens from the "conglomerado osifero" belong to the single species Cardiatherium paranense. In addition, we refer a specimen from Tupungato (Rio de los Pozos Formation, Mendoza) to C. paranense, thus expanding its geographical range. The material from La Pampa represents a different taxon, and is here preliminary referred to Cardiatherium aff. oriental is. Our systematic interpretation of Late Miocene capybaras suggests that the early radiation of this group was not as explosive as previously thought, and was likely constrained by the early acquisition of large size, increasing complexity of the cheek teeth, and probably semi-aquatic habits.
The origins and evolutionary relationships of the pygmy right whale (Caperea marginata), the only living member of the Neobalaeninae, have been the subject of a long-standing debate. This phylogenetic uncertainty is compounded by a limited neobalaenine fossil record. Here, we report a Late Miocene mysticete mandible from Patagonia, Argentina, and provisionally refer it to Neobalaeninae, gen. et sp. indet. The new material represents only the third report of a fossil neobalaenine, and the first fossil occurrence of this lineage in the southwestern Atlantic. It is also the oldest specimen so far reported, thus corroborating the idea of an early divergence time for neobalaenines.
Abstract. PALEOGENE FORAMINIFERA FROM THE PENÍNSULA VALDÉS BOREHOLE (PV.ES-1), NORTHERN PATAGONIA,
ARGENTINA. The PV. es-1 well bored the most complete Cenozoic marine sequence known from the northeastern
Patagonian area. In order to clarify the stratigraphic position of calcareous Paleogene formations
cropping out in the area, the study is focused on the biostratigraphy of the Paleogene foraminiferal assemblages,
which are of very shallow environments and mostly devoid of planktic foraminifera. In the
PV.es-1 borehole between 835-350 meters below surface the following succession of Paleogene assemblages
is recognized: a) three assemblages in the Danian: a cosmopolitan, Midway-type assemblage, and
two assemblages characterized, respectively, by Buliminella isabelleana and Boltovskoyella paleocenica,
both endemic species. b) In the Oligocene, a lower assemblage dominated by Angulogerina, and an upper
assemblage dominated by miliolids, both related to those known from the Elvira Formation (Colorado
Basin), and the San Julián Formation (Austral Basin). c) The Spirosigmoilinella-Martinottiella assemblage,
containing Transversigerina tenua, a guide species of the base of the patagonian transgression, and the
Cribrorotalia hornibrooki assemblage; both assemblages are correlatable with the Gaiman and Monte
León Formations, deposited by the patagonian transgression, of latest Oligocene to early Miocene age. The
inexistence of Eocene assemblages suggests that the Valdes Basin was not covered by the middle Eocene
transgression, as well as onshore San Jorge Basin.
A new genus and species of Ziphiidae, Notoziphius bruneti, gen. et sp. nov., from the late Miocene of Patagonia, is described on the basis of a well-preserved skull and partial left and right dentaries. It can be diagnosed by large, triangular, and markedly asymmetric nasals that strongly point anteroventrally, the ascending process of the maxilla not expanded posteriorly, supraoccipital strongly sloped posteroventrally; elliptical fossa on the nasal process of the premaxilla, small and anterolaterally directed premaxillary crest, and the presence of well-defined alveoli in the maxilla. A phylogenetic analysis including 25 ziphiid genera and 31 characters shows Notoziphius as nested within Ziphiidae in a basal clade with Aporotus, Beneziphius, Messapicetus, and Ziphirostrum. This clade is diagnosed by medial fusion of the premaxillae that closes the mesorostral groove, lateral margin of prenarial basin formed by a thick strip of maxilla, premaxillary crest anterolaterally directed, and reduced contact between nasal and premaxillary crest. The presence of Notoziphius in the Miocene of Patagonia increases our knowledge of ziphiid diversity in South America. Notoziphius bruneti and other Miocene records of ziphiids reinforce the idea that during the Miocene ziphiids were widely distributed and diverse.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline/UJVP
Gois, F., Scillato-Yane, G.J., Carlini, A.A. & Guilherme, E. 2013. A new species of Scirrotherium Edmund & Theodor, 1997 (Xenarthra, Cingulata, Pampatheriidae) from the late Miocene of South America. Alcheringa 37, 175-186. ISSN 0311-5518. A new species of Scirrotherium Edmund & Theodor (Pampatheriidae) is described: S. carinatum. This genus was previously represented by a single species, S. hondaensis Edmund & Theodor, 1997, recorded from the middle Miocene (Laventan) of Colombia. Pampathere remains are common in the Conglomerado osifero' (late Miocene) of the Ituzaingo Formation in the Parana River cliffs of Entre Rios, Chubut (Argentina) and Acre (Brazil). All of them were referred to Kraglievichia paranense, and they are mostly osteoderms. However, only a few of these specimens are strictly consistent with that species. The new species described herein differs from S. hondaensis in having very thin osteoderms with more elaborate ornamentation. The movable band (or imbricate) osteoderms have a sculptured exposed surface and a single transverse row of anterior foramina; the lateral margins are wider and also bear foramina, and the longitudinal central elevation is long and proximally wide, and forms a posteriorly raised crest. This elevation is delimited by a fairly broad and shallow depression on each side, separating the marginal elevation from the longitudinal central one. The exposed surfaces of fixed (or fused) osteoderms bear large and deep anterior foramina, the longitudinal central elevation and delimiting depressions are very pronounced. This new species increases the known diversity of the pampatheres from the Conglomerado osifero'. Additionally, a new nomenclatural scheme for Pampatheriidae osteoderms is proposed.
The Patagonian steppe-a massive rain-shadow on the lee side of the southern Andes-is assumed to have evolved ~15-12 Myr as a consequence of the southern Andean uplift. However, fossil evidence supporting this assumption is limited. Here we quantitatively estimate climatic conditions and plant richness for the interval ~10-6 Myr based on the study and bioclimatic analysis of terrestrially derived spore-pollen assemblages preserved in well-constrained Patagonian marine deposits. Our analyses indicate a mesothermal climate, with mean temperatures of the coldest quarter between 11.4 °C and 16.9 °C (presently ~3.5 °C) and annual precipitation rarely below 661 mm (presently ~200 mm). Rarefied richness reveals a significantly more diverse flora during the late Miocene than today at the same latitude but comparable with that approximately 2,000 km further northeast at mid-latitudes on the Brazilian coast. We infer that the Patagonian desertification was not solely a consequence of the Andean uplift as previously insinuated.
Coastal exposures of the Santa Cruz Formation in southern Patagonia have been a fertile ground for recovery of Early Miocene vertebrates for more than 100 years. This volume presents a comprehensive compilation of important mammalian groups which continue to thrive today. It includes the most recent fossil finds as well as important new interpretations based on 10 years of fieldwork by the authors. A key focus is placed on the paleoclimate and paleoenvironment during the time of deposition in the Middle Miocene Climatic Optimum (MMCO) between 20 and 15 million years ago. The authors present the first reconstruction of what climatic conditions were like and present important new evidence of the geochronological age, habits and community structures of fossil bird and mammal species. Academic researchers and graduate students in paleontology, paleobiology, paleoecology, stratigraphy, climatology and geochronology will find this a valuable source of information about this fascinating geological formation.
Modern pinnipeds distributed along the coasts of continental South America consist almost entirely of otariids (sea lions and fur seals). In contrast, phocids (true seals) are present only on the southernmost extreme of Chile. This recent biogeographic pattern is consistent with the zooarchaeological record (∼8—2 ka), but it is incompatible with the pinniped fossil record during the Neogene. From the middle Miocene to the Pliocene, true seals exclusively dominated pinniped assemblages, and they were only replaced by the fur seals and sea lions sometime after the early Pliocene. Here, we describe pinniped material collected from two new localities in the Atacama Desert, northern Chile, that clarifies this marine mammal faunal turnover. Specifically, these finds provide records of the first occurrence of Otariidae (late Pleistocene) and the last occurrence of Phocidae (early Pliocene) in Chile, which in turn constrain the timing of this turnover to between the early Pliocene and late Pleistocene. The stratigraphic context of these findings provides new insights into hypotheses that explain this faunal turnover in South America, and we briefly discuss them in the context of turnover events involving other marine vertebrates throughout the Southern Hemisphere.
Pectinids are the most abundant and widely distributed taxa in the Tertiary marine beds of Patagonia. Along with other very common molluscan species, they characterize five assemblages, from oldest to youngest: 1) the Oligocene Panopea sierrana-Parinomya patagonensis Assemblage; 2) the Late Oligocene–Early Miocene Jorgechlamys centralis–Reticulochlamys borjasensis Assemblage; 3) the Early Miocene Reticulochlamys zinsmeisteri–Struthiolarella patagoniensis–Pleuromeris cruzensis Assemblage; 4) the Early Miocene Pseudoportlandia glabra–Antimelatoma quemadensis Assemblage; and 5) the latest Early Miocene–earliest Middle Miocene Nodipecten sp.– Venericor abasolensis–Glycymerita camaronesia Assemblage. A brief analysis of the origin and composition of these Tertiary Patagonian molluscan faunas is provided. Striking compositional changes occurred through time, recorded mainly in the Late Paleocene, Late Eocene, Late Oligocene–Early Miocene, and Late Miocene.
The second part of this work contains the descriptions and systematics of gastropods obtained from the upper levels of the Entrerriense Formation (Late Miocene), outcropping at various localities in the Valdes Peninsula, Chubut Province, Argentina. Herein are treated 62 species, of which 37 are new to science, the remainder are either previously described or closely related to described species. Forty-two species are new to the fauna, which consolidates the affinities with the Panamanian, Caribbean, and Neozelandic Bioprovinces.
Fossil seabirds from Early Pliocene (5Ma ago) deposits in SW Cape Province indicate there was a colder, more sub-Antarctic marine environment in this region in the Late Tertiary than at present, thus augmenting similar evidence from molluscs and pinnipeds. The Pliocene seabird fauna included at least 4 species of penguins (Spheniscidae), an albatross (Diomedeidae), two storm-petrels (Oceanitidae), 3 species of prions (Pachyptila), one of which was much larger than any existing member of the genus, several shearwaters (Puffinus and relatives), a diving petrel (Pelecanoides), a booby (Sula) and at least 2 species of cormorants (Phalacrocoracidae). Gulls and terns (Laridae) were present. With the possible exception of the cormorants and larids, all of the elements of the early Pliocene marine avifauna have either become extinct or have retreated from the Cape region. Relatively few other seabirds, such as the gannet Sula (=Morus) capensis and the cormorant Phalacrocorax carbo lucidus have probably established themselves as breeding species in the region subsequently.-from Author
Neoceti is the taxonomic group comprising the two living clades of Cetacea but excluding the extinct Archaeoceti. The two living groups are quite disparate, each distinguished by a unique combination of anatomical and ecological features. The Odontoceti are echolocating macro-predators, whereas Mysticeti are filter-feeders. Ancient cetaceans from Oligocene times (25 to 30 Ma) show skull structures indicative of echolocation in odontocetes and of filter-feeding in mysticetes, emphasizing the early divergence of feeding habits. Apart from the feeding apparatus, however, basal odontocetes and mysticetes are much more similar to one another than are their modern descendants. Similarities include some evolutionary novelties of the skull which are not seen in archaeocetes. Basal odontocetes and mysticetes also show marked similarities with archaic cetaceans, indicating an origin within the archaeocete family Basilosauridae. Odontocetes include 74-75 living species in the families Physeteridae, Kogiidae, Ziphiidae, Platanistidae, Delphinidae, Phocoenidae, Monodontidae, Iniidae, Pontoporiidae, and Lipotidae. Phylogenetic analyses based on molecules, anatomy, and fossils indicate that the Odontoceti is monophyletic. Mysticetes include 13-14 living species in the families Balaenidae, Neobalaenidae, Balaenopteridae, and Eschrichtiidae. Phylogenetic analyses based on molecules, anatomy, and fossils indicate that the Mysticeti is monophyletic. Unlike living species, fossil mysticetes are not recognized by the presence of baleen because, though this probably occurred in most extinct species, it rarely preserves. Some early fossil odontocetes and mysticetes have features similar or even identical to those seen in some basilosaurid archaeocetes.
Nuevo aporte al conocimiento de la edad de la Formación Paraná, Mioceno de la provincia de Entre Ríos, Argentina
We describe a new large species of marabou stork, Leptoptilus patagonicus (Ciconiiformes, Ciconiidae, Leptoptilini), from the late Miocene Puerto Madryn Formation, Chubut Province, Argentina. The specimen consists mainly of wing and leg bones, pelvis, sternum, cervical vertebrae, and a few fragments of the skull. We provisionally adopt the traditional systematic scheme of ciconiid tribes. The specimen is referred to the Leptoptilini on the basis of similarities in morphology and intramembral proportions with the extant genera Ephippiorhynchus, Jabiru, and Leptoptilos. The fossil specimen resembles in overall morphology and size the species of Leptoptilos, but also exhibits several exclusive characters of the sternum, humerus, carpometacarpus, tibiotarsus, and pelvis. Additionally, its wing proportions differ from those of any, living taxon, providing support to erect a new species. This is the first record of the tribe Leptoptilini in the Tertiary of South America.
Collon Cura Formation has been identified in this area by the presence of Pilcaniyeu Ignimbrite (Middle Member). The Upper and Lower Members of this formation, where fossils were found, are mainly reworked pyroclastic rocks, probably deposited simultaneously with the ignimbrite. The following taxa are described: Neosteiromys? tordillense gen. et sp. nov. Erethizontidae); Maruchito trilofodonte gen. et sp. nov., Protacaremys denisae sp. nov., Acarechimys sp. (Echimydae) and Dasyproctidae indet. Based on the rodents, the following sequence of faunas is proposed: Santacrucian, Frisian s.s., Colloncuran s.s. and Mayoan. The Mayoan rodents have affinities with those of the Chasicoan, while the rodents of the other faunas are more related to each other. The study suggests a hiatus within the Friasean Land-Mammal Age. -from English summary
A penguin humerus constitutes the most recent record of the widely distributed genus Palaeospheniscus in the Atlantic Ocean. Penguins are unknown in late Miocene and Plicene beds in the region, whereas they have been reported from the occidental coasts of the continent. The gap in the record is occasioned mainly by the dearth of beds of this age. The present finding confirms that a high diversity still existed in the middle Miocene. © 2012 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.
Portheus patagonicus Ameghino, 1901, described on the basis of an isolated tooth from the Leonian Stage (Upper Oligocene–Lower Miocene) of Patagonia, was interpreted as belonging to an ichthyodectiform fish. Recently, the holotype was relocated and an additional tooth was found. Comparison of both specimens and some additional information permit the identification of the teeth as belonging to a delphinoid cetacean of the family Kentriodontidae. This is the first report of this family in the southern Atlantic region.
The Paleogene to Neogene San Julián and Monte León formations underlie the central and eastern parts of the Austral Basin (Patagonia, Argentina), and represent coastal plain to shallow shelf systems within a retroarc foreland basin east of the Andes. The formations are characterized by prominent occurrences of thin (<1 m) densely compacted fossil concentrations, including the large oyster Crassostrea? hatcheri. Formation ages have been problematic given macrofaunal provincialism effectively precluding precise extrabasinal correlations. A Sr-isotope chronostratigraphy based on fossil shell calcite from oysters, pectinids and brachiopods is presented for a regional NE–SW-oriented transect extending ∼200 km along strike of the Austral Basin. The Paleogene–Neogene boundary (∼23 Ma) may occur within the uppermost San Julián Formation (22.68 Ma, with a range between 22.22 and 23.22 Ma), coincident with a prominent glauconitic interval, or in a meteorically altered erosional paleosurface that caps this formation and may correlate with an eustatic sea level fall coincident with the global boundary. The younger Monte León Formation is entirely of early Neogene (Aquitanian to early Burdigalian) age, with ages of 22.12 Ma (21.68–22.58) at the base to 17.91 Ma (17.51–18.29) at the top. The proposed new chronostratigraphic framework forms a foundation for future differentiation of local, regional, and global sedimentary patterns in the Austral Basin during the Paleogene/Neogene transition; in particular, with contemporaneous basins and tectonic blocks across the southern polar region, such as in Australia, New Zealand, and Antarctica.