The record of Paleogene ungulates and the demise of the South America-Antarctica land connection (original) (raw)
Related papers
Global and Planetary Change, 2014
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 places 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 (~56-57 m.y.). This faunistic isolation is documented to have occurred at least 25 Ma before the existence of deep-water circulation conditions in Drake Passage (~30 m.y.) based on the onset of seafloor spreading in the west Scotia Sea region. We hypothesize that in the early stages of extension (Late Paleocene, ~55 m.y.) a wide 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.
A new 'South American ungulate' (Mammalia: Litopterna) from the Eocene of the Antarctic Peninsula
Geological Society, London, Special Publications, 2006
Notolophus arquinotiensis, a new genus and species of the family Sparnotheriodontidae (Mammalia, Litopterna), is represented by several isolated teeth from the shallow-marine sediments of the La Meseta Formation (late Early-Late Eocene) of Seymour Island, Antarctic Peninsula, which have also yielded the youngest known sudamericids and marsupials. The new taxon belongs to the extinct order of 'South American native ungulate' Litopterna characterized by the convergence of the later forms with the equids and camelids. Notolophus arquinotiensis shows closest relationships with Victorlemoinea from the Itaboraian (middle Palaeocene) of Brazil and Riochican-Vacan (late Palaeocene-early Eocene) of Patagonia, Argentina. Although still poorly documented, this new taxon shows that the early Palaeogene Antarctic faunas might provide key data concerning the problems of the origin, diversity and basal phylogeny of some of the 'South American ungulates' (Litopterna). This new taxon shows the importance of Antarctica in the early evolution of the ungulates and illustrates our poor state of knowledge.
Antarctica as Background for Mammalian Evolution
DOAJ (DOAJ: Directory of Open Access Journals), 2015
Since the 1980's, a series of new Cretaceous-Paleogene land mammals has been found in southern continents. They drastically changed the traditional perspective of how mamrnals evolved all over the world, and particularly, how they evolved in the southern continents. This paper is a preliminary evaluation of how much this new evidence contributes to an understanding of the role Antarctica played both in the evolution of mammals in general, and in the evolution of marnrnals in southern continents, in particular. The only land marnmals thus far recorded in Antarctica come from middle to late Eocene beds of the La Meseta Formation on Seymour Island (Antarctic Peninsula). But the land mammals found in southern South America (Patagonia) and Australia, spanning the Cretaceous-Paleogene, strongly suggest that Antarctica was both an important evolutionary center (at least during the Cretaceous-Eocene), and a "stepping stone" between both continents during the Late Cretaceous-carly Paleocene. The taxonomic di versification of monotremes in Australia (represented by at least two Early Cretaceous families, which make four families between that time and the Recent), and the oldest marine barrier between Australia and Antarctica (ea, 64 Ma), indicate that monotremes probably originated and diversified in the Australian/ Antarctic sector of Gondwana. The single dispersal (an ornithorhynchid) to the South American sector before or during the early Paleocene, attests to the role of Antarctica as a "srepping stone" between Australia and South America. The immigration of marsupials to the Australian sector of Gondwana must have occurred before 52 Ma. Thus, the "Australian marsupials" probably also diversified in the AustralianlAntarctic sector of Gondwana. The available paleontological and biochemical data suggest that species ancestral to some of the present Australian marsupials evolved in Antarctica prior to their entry into Australia. The idea of the Australian/ Antarctic sector as the area of origin and diversification of monotrernes, and their absence from the Late Cretaceous (Campanian) land-marnrnal communities of southern South America (otherwise, exclusively composed by other non-tribosphenic and pre-tribosphenic mammals), suggest that by the end of the Mesozoic, there was a regional biogeographical differentiation between the East Gondwanan continents. Thus, Antarctica also might have been an important evolutionary center for non-tribosphenic and pre-tribosphenic mammals throughout the later part of the Mesozoic. The Eocene land marnmals from La Meseta Formation pertain to "South American" lineages of marsupials (at least 4 families) and placentals (tardigrades and ungulates). They are characterized by a marked endemism at the specific and generic leve!. This endemism and the earlier record of certain taxa than in South America suggest both that the diversification of "South American" Tribosphenida mamrnals occurred in the Antarctic/South American sector of Gondwana, and that after the Paleocene, the Antarctic continent, or part of it, was isolated.
Antarctic Science, 2017
Here we describe a new terrestrial mammal from the Eocene of Seymour Island (Isla Marambio) represented by a lower left third molar and assigned to a new species of Sparnotheriodontidae, an ungulate family with a broad palaeobiogeographical distribution in South America. The specimen was found in the Cucullaea I allomember of the La Meseta Formation, in a new mammalian locality (IAA 2/16). Notiolofos regueroi sp. nov. shares a brachyodont, lophoselenodont and bicrescentic molar pattern with N. arquinotiensis, recorded for a stratigraphic sequence of 17.5 Ma in Antarctica. The criteria for the species differentiation are the absence of mesial and labial cingulids, the larger paraconid, the wider talonid basin, the accentuated distal projection of the hypoconulid, the centroconid development and the smaller size. Together with the astrapotherian Antarctodon sobrali, they represent the medium to large terrestrial mammals of the early Eocene Antarctic landscape that was mostly dominated...
Advances in Polar Science, 2019
The fossil record of terrestrial mammals in Antarctica is temporally and geographically constrained to the Eocene outcrops of La Meseta and Submeseta formations in Seymour (Marambio) Island in West Antarctica. The faunal assemblage indicates a clear South American imprint since all the groups have a close phylogenetic relationship with Cretaceous and Paleogene mammals from Patagonia. Despite the presence of several mammalian taxonomic groups: Dryolestida, Gondwanatheria, Eutheria and Metatheria, the presence of other major mammalian taxa should be expected and will probably be confirmed by new findings. Placental mammals with an inferred body mass between 10 to 400 kg in size, are represented by xenarthrans, and two groups of the so called South American native ungulates: Astrapotheria and Litopterna. The Metatheria are the smaller (less than 1 kg) and most abundant components of the fauna. Marsupials are represented by derorhynchid ameridelphians, several microbiotherian australidelphians (both microbiotheriids and woodburnodontids), and ?glasbiid prepidolopod and polydolopid polydolopimorphians. Plus, there are remains of several mammalian teeth of indeterminate phylogenetic affinities. The present knowledge of the Southern Hemisphere mammalian evolution and paleogeographic change through time, indicates that Antarctica played a major role for land mammals, at least since the Jurassic. The actual representation of Paleogene terrestrial mammals in Antarctica is most probably biased, as all the evidence indicates that australosphenidan mammals should be present in this continent since the Jurassic.
The fossil record of Antarctic land mammals: commented review and hypotheses for future research
2019
The fossil record of terrestrial mammals in Antarctica is temporally and geographically constrained to the Eocene outcrops of La Meseta and Submeseta formations in Seymour (Marambio) Island in West Antarctica. The faunal assemblage indicates a clear South American imprint since all the groups have a close phylogenetic relationship with Cretaceous and Paleogene mammals from Patagonia. Despite the presence of several mammalian taxonomic groups: Dryolestida, Gondwanatheria, Eutheria and Metatheria, the presence of other major mammalian taxa should be expected and will probably be confirmed by new findings. Placental mammals with an inferred body mass between 10 to 400 kg in size, are represented by xenarthrans, and two groups of the so called South American native ungulates: Astrapotheria and Litopterna. The Metatheria are the smaller (less than 1 kg) and most abundant components of the fauna. Marsupials are represented by derorhynchid ameridelphians, several microbiotherian australide...
Eocene land mammals from Seymour Island, Antarctica: palaeobiogeographical implications
Antarctic Science, 1994
Middle Eocene land mammals from La Meseta Formation, Seymour (Marambio) Island are reviewed. A taxonomically diverse fossil land-vertebrate assemblage with small and medium-size mammals has been recovered from four localities. The depositional setting is shallow marine and most of the mammal-bearing beds are in reworked, moderate to high energy subtidal facies. The characteristics of these mammals not only confirm but also strengthen the biogeographical relationships between southern South America (Patagonian Province) and the Antarctic Peninsula during the Paleogene and rule out the possibility of a major barrier between these areas. The Antarctic ungulates (Astrapotheria and ?Litopterna) are plesiomorphics in retaining low crowned cheek teeth and are more similar to those from the Pancasamayoran local faunas of southern South America (Patagonia).
Journal of South American Earth Sciences, 2021
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 nontherian lineages into southern South America; later, the migration of metatherians to Australasia.
The oldest mammals from Antarctica, early Eocene of the La Meseta Formation, Seymour Island
Palaeontology, 2014
New fossil mammals found at the base of Acantilados II Allomember of the La Meseta Formation, from the early Eocene (Ypresian) of Seymour Island, represent the oldest evidence of this group in Antarctica. Two specimens are here described; the first belongs to a talonid portion of a lower right molar assigned to the sparnotheriodontid litoptern Notiolofos sp. cf. N. arquinotiensis. Sparnotheriodontid were medium-to large-sized ungulates, with a wide distribution in the Eocene of South America and Antarctica. The second specimen is an intermediate phalanx referred to an indeterminate Eutheria, probably a South American native ungulate. These Antarctic findings in sediments of 55.3 Ma query the minimum age needed for terrestrial mammals to spread from South America to Antarctica, which should have occurred before the final break-up of Gondwana. This event involves the disappearance of the land bridge formed by the Weddellian Isthmus, which connected West Antarctica and southern South America from the Late Cretaceous until sometime in the earliest Palaeogene.
Journal of Mammalian Evolution, 2018
A new Paleogene metatherian from locality IAA 1/90, Marambio (Seymour) Island in the Antarctic Peninsula is described. Pujatodon ektopos, gen. et sp. nov., is recognized on the basis of a tiny lower left molar recovered from early Eocene (late Ypresian) levels of the Cucullaea I Allomember, La Meseta Formation. The tooth is characterized by its small size, bunoid aspect, short trigonid with closely set paraconid and metaconid, wide and long talonid, the development of an incipient cingulid at the labial base of the crown between the trigonid and talonid, and an expanded posterior cingulid. Body mass estimations for the new taxon range from 83.13 to 153.15 g. Its enamel microstructure shows the earliest evidence among metatherians of aligned prisms, as well as of interprismatic sheets of matrix. The analysis of other parameters, like body mass, molar morphometric index, and wear facets, suggests that the molars of Pujatodon were primarily adapted to the processing of fruits, nuts, seeds, and/or hard insects. Several features suggest the allocation of this specimen among basal polydolopimorphians (Prepidolopidae or, more probably, Glasbiidae). The discovery of the specimen MLP 14-I-10-20 could offer new insights on the origins and early diversification of Australidelphian marsupials in southern (and northern?) continents. It also adds significant information on the diversity of Antarctic Paleogene mammals, their evolution, habits, and historical biogeography.