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Episodes in South American Land Mammal Evolution and Sedimentation: Testing Their Apparent Concurrence in a Paleocene Succession from Central Patagonia
... Paleogene continental sequences from the San Jorge Basin, central Patagonia, Argentina, are globally significant due to their extraordinary preservation of South American fossil faunas (e.g.,Simpson, 1935aSimpson, , 1935bSimpson, , 1948Cifelli, 1985;Pascual and Ortiz-Jaureguizar, 1990;Bonaparte et al., 1993;Bond et al., 1995;Flynn and Swisher, 1995;Ortiz-Jaureguizar and Cladera, 2006;Gelfo et al., 2009;Madden et al., 2010;Woodburne et al., 2014aWoodburne et al., , 2014b) and floras (Berry, 1937;Romero, 1968;Archangelsky, 1973Archangelsky, , 1976Petriella and Archangelsky, 1975;Archangelsky and Zamaloa, 1986;Zamaloa and Andreis, 1995;Brea et al., 2005Brea et al., , 2007Brea et al., , 2008Brea et al., , 2011Iglesias et al., 2007;Zucol et al., 2010). These sequences also provide rec ords of regional biotic responses to global climatic events (e.g.,Raigemborn et al., 2009Raigemborn et al., , 2014Bellosi and González, 2010;Krause et al., 2010;Dunn et al., 2015;Selkin et al., 2015). ...
... The rocks composing the Peñas Coloradas Formation are mainly medium-dark reddish, cross-bedded sandstones, related to sinuous channel filling, and subordinate mudstones and tuffs deposited in floodplain settings (e.g.,Raigemborn et al., 2009Raigemborn et al., , 2010Comer et al., 2015). According toBond et al. (1995) and Woodburne et al. (2014a, 2014b), among others, the Peñas Coloradas Formation contains vertebrate remains from the " Carodnia faunal zone, " originally described bySimpson (1935aSimpson ( , 1935b) from Bajo Palangana and Cerro Redondo (Fig. 1B); however, this fauna is probably contained within the Las Flores Formation (see Discussion). Fossil wood has also been described from the Peñas Coloradas Formation in the area around the town of Sarmiento and at Punta Peligro along the coast (Brea et al., 2004;Brea and Zucol, 2006;Raigemborn et al., 2009). ...
... The muddy facies contain evidence of pedogenic processes, such as mottles and rhizo liths. Fossils in the study area include vertebrate remains that are attributed to the Itaboraian SALMA (Bond et al., 1995;Goin et al., 2009;Woodburne et al., 2014b) and phyto lith remains (Brea et al., 2008;Raigemborn et al., 2009). Crocodilian coprolites were also described from the Las Flores Formation in the coastal area of Pico Salamanca, 4–5 km to the east of Bajo Palangana (Krause and Piña, 2012). ...
The Río Chico Group in the San Jorge Basin of central Patagonia (Argentina) preserves some of South America’s most significant Paleogene records of biotic and climatic change. Three of its constituent formations, the Peñas Coloradas, Las Flores, and Koluel-Kaike, host vertebrate faunas referred to the “Carodnia faunal zone,” the Itaboraian South American Land Mammal Age (SALMA), and the Riochican SALMA. However, the precise absolute ages of these units, and thus their associated faunas and paleoclimate records, are poorly resolved. Herein, we report new paleomagnetic and geochronologic results from these formations in south-central Chubut Province, Argentina. U-Pb dating of four volcanic ashes, using both laser ablation–multicollector–inductively coupled plasma–mass spectrometry and high-resolution chemical abrasion–isotope dilution–thermal ionization mass spectrometry, indicates ages of igneous crystallization of 51.403 ± 0.037 (0.045) [0.071] Ma for a level within the middle Las Flores Formation and 46.714 ± 0.012 (0.026) [0.057] Ma, 44.579 ± 0.013 (0.026) [0.054] Ma, and 42.856 ± 0.017 (0.027) [0.054] Ma for levels in the lower, middle, and upper Koluel-Kaike Formation, respectively. Combining these with previous isotopic ages in our new magnetostratigraphic framework, we correlate the Peñas Coloradas Formation to chrons C27n-26r (ca. 62.5 to ca. 61.6 Ma; late Danian) and the section from the middle Las Flores to the uppermost Koluel-Kaike to chrons C23n to C19r (ca. 51.4–42.2 Ma; mid Ypresian–late Lutetian). We combine these data with other recently published chronostratigraphic results from Paleogene units in Patagonia to better constrain the ages of noteworthy Paleogene plant and mammal fossil sites in Patagonia and to develop a revised temporal calibration of the Las Flores, Vacan, and “Sapoan” faunas.
... The seven therians comprise four marsupials and three placentals. Punta Peligro marsupials are represented by two Didelphimorphia?, Derorhynchus and Didelphopsis and two new genera of Polydolopidae and Bonapartheriidae (Bond et al., 1995; Pascual and Ortiz-Jaureguizar, 2007). Eutherians are represented by the notonychopid Requisia vidmari, the oldest known litoptern (Bonaparte and Morales, 1997). ...
... Simpson (1935a) suggests that " Carodnia zone " could be approximately equivalent or probably somewhat older than the lower level from Cerro Redondo. No common taxa were found in this last locality, which contains an undetermined ?borhyaenid, the proterotheriid litoptern Wainka tshotse (Bond et al., 1995) and Amphidolops yapa, a polydolopid marsupial (see Chornogubsky, 2010). The " Carodnian " fauna is the oldest from Patagonia that was known to Simpson (1935a,b). ...
... The " Carodnian " fauna is the oldest from Patagonia that was known to Simpson (1935a,b). Vertebrates from these horizons are apparently restricted to the Peñas Coloradas Formation in the San Jorge Basin, but there is no clear evidence that they could represent a new biochronologic unit (Bond et al., 1995; Gelfo et al., 2009a). Near Laguna del Hunco and the town of Paso del Sapo in the Chubut province, Argentina (Fig. 6) there are local mammalian faunas dated as Early–Middle Eocene (∼49–47 m.y.), filling the temporal gap between the faunas of the Río Chico Group and those of the Sarmiento Formation in Patagonia and providing a record of probable rainforest vertebrates (Gosses, 2006; Tejedor et al., 2009). ...
The biogeographic hypothesis more accepted today is that Antarctica (West Antarctica) and southern South
America (Magellan region, Patagonia)were connected by a long and narrow causeway(Weddellian Isthmus) between the Antarctic Peninsula and South America since the Late Cretaceous (Campanian) until the Early Paleogene allowing terrestrial vertebrates to colonize new frontiers using this land bridge. Stratigraphically
calibrated phylogenies including large, terrestrial native ungulates Litopterna and Astrapotheria taxa reveal
long ghost lineages that extended into the Late Paleocene and provide evidence for the minimum times at
which these “native ungulates” were present both on Antarctica and South America. Based on these results we
estimate that the Weddellian Isthmus was functional as a land bridge until the Late Paleocene. Our data place
the disconnection between Antarctica and South America in the Late Paleocene, indicating that the terrestrial faunistic isolation (Simpson's “splendid isolation”) in South America begun at the end of the Paleocene (~56 to
57 m.y.). This faunistic isolation is documented to have occurred at least 25 Ma before the existence of deepwater circulation conditions in Drake Passage (~30 m.y.) based on the onset of seafloor spreading in the west Scotia Sea region.Wehypothesize that in the early stages of extension (Late Paleocene, ~55 m.y.) awide and relatively shallow epicontinental sea developed between the Antarctic Peninsula and South America drowning the Weddellian Isthmus and preventing the faunal interchange for obligate cursorial terrestrial forms.
... More recently, Ladevèze and de Muizon (2010) suggested a sister-group relationship of Minusculodelphis and Monodelphopsis plus dasyurids, as representatives of the Australasian Eometatheria. Besides the Itaboraí fauna, the genus Minusculodelphis has also been recorded in the Itaboraianaged locality of Las Flores, in central Patagonia, Argentina (Bond et al. 1995; Goin et al. 1997; Woodburne et al. 2014). Here, we describe a new species of Minusculodelphis and discuss its affinities, dental morphology, and paleobiological features; among the latter, aspects of its inferred diet and body size are considered. ...
With less than 3 g of estimated body mass, the early Eocene Minusculodelphis minimus Paula Couto (Mammalia, Metatheria, Jaskhadelphyidae) is one of the smallest mammals, living or extinct. It has alternatively been regarded as a didelphid or a derorhynchid Bameridelphian,^ or even as an eometatherian marsupial. Here, we describe a new species of Minusculodelphis coming from the same locality (Itaboraí Quarry, Brazil) and age (Itaboraian age) of the type species of the genus. It differs from M. minimus in its larger size and several dental characters. The new species offers data on the upper dentition and femur, which are unknown in the type species. Compared to other Paleogene metatherians, Minusculodelphis shows closer relationships with Jaskhadelphys, from the early Paleocene of Tiupampa, Bolivia, as well as with Kiruwamaq, from the late Eocene early Oligocene of Perú. A cladistic analysis places all three genera within the family Jaskhadelphyidae (Metatheria, Order indet.), which includes small to tiny, insectivorous-like
metatherians. We argue that insectivory (soft insects) is the best-supported diet for both species of Minusculodelphis, and that the most probable microhabitat for them was the understorey or leaf litter of tropical, rain forested environments.
The Santa Bárbara Subgroup of the Salta Group in northwestern Argentina represents a key sedimentary record to understand the geological, biological, and climatological changes that occurred in South America during the Paleogene. However, the lack of absolute ages in these non-marine successions have prevented conclusive interpretations and correlations at a regional-scale. In this contribution, we present an integrative study based on sedimentological and stratigraphic approaches, a paleontological review, and, for the first time, an absolute age from a tuff level in the upper section of the Mealla Formation. We propose the following scenario: 1) Cycles of low and high accommodation stages that can be tracked at basin-scale providing a criterion to regional correlations; 2) An U–Pb zircon age of 58 Ma, which combined with previously estimated ages for Santa Bárbara Subgroup indicate that this unit is constrained between 61 and 49? Ma; 3) On view of this new age the fossil-bearing levels of the Mealla Formation fill a hiatus of more than 4 Myr in the South American vertebrate record for the middle to late Paleocene, reshaping our understanding of the early evolutionary stages of this fauna. Our results represent a robust first step to achieve reliable regional correlations and an integrative comprehension of the evolution of the Salta Basin and its fossil biota.
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.
Here we present an update of the fossil record the Crocodylia of Argentina, which is represented by Caimaninae alligatorids and Gavialoidea. Less diverse, gavialoids are recorded by a single species, Gryposuchus neogaeus, from the late Miocene of Northeast Argentina. On the other hand, alligatoroids recorded two important moments in its natural history, one at the beginning of the Paleogene (Late Paleocene–Middle Eocene) and the other in the Neogene (Late Miocene). The most ancient record of alligatoroids in South America comes from the Early Paleocene of Patagonia. It includes basal forms of caimanines such as Necrosuchus ionensis, Eocaiman palaeocenicus, Eocaiman cavernensis, and probably a new species of alligatoroid, which provide key morphological information on the evolutionary and biogeographic history of these crocodylians. Another important moment of the evolutionary history of caimanines is the diversification of the lineage, observed during the Miocene. Although there is some isolated cranial material of this group from the Late Miocene of northwestern Argentina, the most abundant and diverse fossil material comes from the northeast, from a level called “Conglomerado Osífero”. Two genera of caimanines are known from this stratigraphic level (Caiman and Mourasuchus) with at least five valid species.
We summarize the configuration of plates, geographical barriers, and possible dispersal events during the Late Cretaceous–Cenozoic between North and South America, the Caribbean, Antarctica, and Australia. The arrival of metatherians in South America was a Late Cretaceous event, and probably a Maastrichtian one. There are few doubts that the first metatherians in this continent arrived from North America. We suggest that not only eutherian mammals but also metatherians may have reached South America from the north in a series of successive dispersal waifs. This FABI (First American Biotic Interchange) may have replicated the successive waif dispersal mood of the late Cenozoic GABI (Great American Biotic Interchange). The initial radiation of basal South American metatherian lineages (“Ameridelphia”) may have already occurred by Late Campanian-Maastrichtian times. We also suggest that a cooling pulse happening by the Latest Cretaceous (Late Maastrichtian, ca. 68–67 Ma) may have been involved in the origin of the Australidelphia, as part of the southern (Austral Kingdom) Nothofagus biota. Four out of six faunal phases were involved in the evolution of South American metatherians: (1) Early South American (Late Cretaceous to the Late Eocene), Late South American (Early Oligocene to late Miocene), Interamerican (Plio–Pleistocene), and Hypoamerican (Holocene). The first of these phases involved the arrival and expansion of many lineages and adaptive types. The global cooling by the Eocene–Oligocene Boundary implied the extinction of many (mostly tropical) lineages, as well as the diversification of several specialized ones. The third of these faunal phases transpired during a time lapse of ecological imbalance and global cooling, while the last phase saw already much impoverished metatherian associations throughout the continent.
The fossil record of Alligatoroidea in Argentina is mainly represented by Caimaninae alligatorids. This lineage recorded two important
moments in its natural history, one at the beginning of the Paleogene (Late Paleocene–Middle Eocene) and the other in the Neogene (Late
Miocene). The most ancient record of alligatoroids in South America comes from the Early Paleocene of Patagonia. It includes basal forms of
caimanines such as Necrosuchus ionensis, Eocaiman palaeocenicus, Eocaiman cavernensis, and probably a new species of alligatoroid, which
provide key morphological information on the evolutionary and biogeographic history of these crocodylians. Another important moment of the
evolutionary history of caimanines is the diversification of the lineage observed during the Miocene. Although there is some isolated cranial
material of caimanines from the Late Miocene of northwestern Argentina, the most abundant and diverse fossil Miocene material comes from
the northeast, from a level informally called “Conglomerado Osífero”. Two genera of caimanines are known from this stratigraphic level
(Caiman and Mourasuchus) with at least five valid species. Here we present an update of the knowledge of Cenozoic alligatorids of Argentina,
as a tribute to Zulma Gasparini for her invaluable contribution to the understanding of the crocodilian evolution in South America.
Ferugliotherium windhauseni Bonaparte 1986a, the only known species of the Ferugliotheriidae, is the first multituberculate recognized from South America. It is known from the previously described holotype ml and 12 additional isolated teeth (m1, M1, and, tentatively, three lower incisors, one lower premolar, four upper incisors, and two upper premolars), which we describe here. All of the specimens were discovered in the Campanian Los Alamitos Formation of Argentina at one locality, Estancia Los Alamitos. Two other teeth, a purported lower premolar and a large lower incisor, both from the same locality and both previously referred to F. windhauseni, probably do not belong to that taxon. The lower premolar is unidentifiable and the lower incisor is probably referable to Gondwanatherium patagonicum. We regard two worn specimens previously identified as upper molars and comprising the hypodigm of Vucetichia gracilis Bonaparte, 1990 as probable mis of F. windhauseni. Vucetichia, previously assigned to the Gondwanatheriidae, is therefore probably a junior synonym of Ferugliotherium but formal synonymy is deferred pending the recovery of more nearly complete m1s of Ferugliotherium and/or less worn molars of Vucetichia.The gross dental morphology of the new specimens and the inferred pattern of jaw movement help to confirm the multituberculate affinities of F. windhauseni. The Ferugliotheriidae is more derived than the Haramiyoidea and Paulchoffatoidea but probably still retained more than two lower premolars and generally low cusp formulae on m 1 and M 1; these characteristics indicate that a cimolodont grade of organization had not been attained. The family, tentatively assigned to the Plagiaulacoidea, is considered a derived member of that group, possibly most closely related to an undescribed genus from the Upper Jurassic Morrison Formation. In other characters (e.g., presence of fully restricted band of enamel on central incisors, development of lingual row of cusps on M1, large size of m1 relative to m2), ferugliotheriids resemble either taeniolabidoids or ptilodontoids, or both. The Ferugliotheriidae differ from all other known multituberculates in possessing prominent transverse ridges and furrows on the molars. This unique mosaic of attributes indicates a significant interval of isolation from Laurasian populations.
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