Brenda S. Ferrero

A NEW UPPER PLEISTOCENE TAPIR FROM ARGENTINA: REMARKS ON THE PHYLOGENETICS AND DIVERSIFICATION OF NEOTROPICAL TAPIRIDAE

Abstract A complete skull of a fossil tapir (Perissodactyla: Tapiridae) was recovered from outcrops of the Arroyo Feliciano Formation (Late Pleistocene; Lujanian Age) in the Argentine Mesopotamia and is here recognized as a new species. The phylogenetic relationships of this new taxon, Tapirus mesopotamicus sp. nov., are revealed by cladistic character analysis using several extinct and extant taxa. The taxa included in the analysis are the extinct genera Miotapirus, Paratapirus, and Plesiotapirus, five North American paleospecies Tapirus veroensis, T. haysii, T. johnsoni, T. webbi, and T. polkensis, and all the living species of the genus Tapirus (T terrestris, T. pinchaque, T. bairdii, and T. indicus). Tapirus mesopotamicus sp. nov is diagnosed by having a robust and long skull with short rostrum relative to total length of cranium, a single and not arched sagittal crest, broad table of frontals on the anterior skull roof, temporal crests converging very near the frontal-parietal suture, palate very arched, premaxilla deeply notched above canine, maxilla and base of zygomatic process strikingly robust, P1 short and quadrangular, and mandibular condyle slender with posterior wall flat or somewhat concave. The resulting cladogram depicts a well-supported clade comprising the South American tapirs. The new taxon T. mesopotamicus sp. nov. groups with its sister taxon T. pinchaque, and together with T. terrestris, form a sister clade to T. bairdii and three North American fossil tapirs.

A Pleistocene Giant River Otter from Argentina: Remarks on the Fossil Record and Phylogenetic Analysis

Abstract The fossil record of Neotropical Lutrinae is very incomplete, with a few specimens of Lontra and three records of Pteronura. The published records of Pteronura correspond to remains of Pteronura sp. from Lujanian beds in Entre Ríos province (Argentina) and P. brasiliensis found in the “Late Pleistocene” of Brazil, but they lack stratigraphic context and their age could range from at least 380–0.9 Ka. P. brasiliensis, the giant river otter, inhabits rivers and lakes of northern central South America, and has been related to the North American fossil otter Satherium. In this work we describe and compare a very complete specimen of Pteronura found in Entre Ríos province using classical morphological descriptive and multivariate analyses, discuss the importance of this specimen for the fossil record of the taxon, and perform a preliminary phylogenetic analysis. The specimen agrees in morphometric and qualitative characters with the recent species P. brasiliensis, but is slightly larger and presents some minor differences in skull and dental morphology. These differences are interpreted as intraspecific variation, thus the fossil is interpreted as P. brasiliensis. In the phylogenetic analysis, the studied specimen clusters with P. brasiliensis, corroborating the taxonomic determination and supporting a relationship between Satherium and Pteronura. The specimen is the first fossil record of the genus for Argentina, and the oldest corroborated record, with a 130–125 Ka tentative age.

Reappraisal of the Genus Tapirus (Perissodactyla, Tapiridae): Systematics and Phylogenetic Affinities of the South American Tapirs

The record of the genus Tapirus in South America is associated with the faunistic events of the Great American Biotic Interchange (GABI). The taxon is considered an immigrant of Holarctic origin. Although remains are scarce and incomplete during the Pleistocene, an analysis of these materials allowed us to consider valid seven fossil species : Tapirus tarijensis, T. cristatellus, T. greslebini, T. rioplatensis, T. oliverasi, T. mesopotamicus, and T. rondoniensis. A phylogenetic analysis was carried out in order to elucidate the relationships of the American fossil and extant species. Our result is consistent with a paraphyletic hypothesis for South American tapirs and suggests that a second dispersal event would have occurred from South America to North America, of a form closely related to T. cristatellus, resulting in the derived forms of North America.

Mylodon darwini Owen (Xenarthra, Mylodontinae) from the Late Pleistocene of Mesopotamia, Argentina, with remarks on individual variability, paleobiology, paleobiogeography, and paleoenvironment

ABSTRACT The subfamily Mylodontinae, typified by Mylodon, is known from the Colloncuran (late Miocene of Patagonia, Argentina) to the late Pleistocene of South America and North America. Mylodontinae have been recorded during the Pleistocene of Argentina, including the genera Glossotherium, Paraglossotherium, Lestodon, and Mylodon, with Paraglossotherium and Mylodon not as well known as the other genera. In Argentina there have been traditionally four species of Mylodon, M. darwini, M. zeballozi, M. listai, and M. insigne, although the validity of some has been considered doubtful. A nearly complete skull with an associated mandible of Mylodon darwini from the late Pleistocene of Mesopotamia, Argentina, is described. The specimen represents the first record of the species in the Mesopotamian region. The morphometric analysis indicates that M. darwini had greater individual variability than previously thought. Although based on the results of the morphologic and morphometric analysis, the idea of sexual dimorphism for M. darwini is, for the time being, unwarranted. This new record also supports the idea that Mylodon had great ecological tolerance and was capable of inhabiting climates ranging from cold and arid to warm and humid, and even montane environments.

Taxonomic reinterpretation of Theosodon hystatus Cabrera and Kraglievich, 1931 (Litopterna, Macraucheniidae ) and phylogenetic relationships of the family

ABSTRACT Associated fragments of a maxilla and mandible of Theosodon hystatus Cabrera and Kraglievich (Macraucheniidae, Litopterna) from the late Miocene Arroyo Chasicó locality (Buenos Aires Province, Argentina) are described and taxonomically reinterpreted. The systematic arrangement is supported by the first phylogenetic analysis of the family. The holotype (MLP 29-IX-1-75) of T. hystatus was originally poorly described and its generic assignation was not fully justified. The comparison of MLP 29-IX-1-75 with Paranauchenia denticulata Ameghino from the ‘Mesopotamiense’ (lower member of the Ituzaingó Formation, Entre Ríos Province; late Miocene) shows significant morphological similarities that lead us to propose that T. hystatus belongs to the genus Paranauchenia Ameghino, resulting in the new combination Paranauchenia hystata. The phylogenetic analysis of Macraucheniidae supports this proposal because both taxa form a monophyletic clade, sharing one synapomorphy: metaconid of m2 lingually placed. This new taxonomic interpretation implies the geographic extension of Paranauchenia to Buenos Aires Province. The obtained phylogeny also corroborates the monophyly of Macraucheniidae, but not that of the currently considered subfamilies, because Cramaucheniinae is paraphyetic.

FOSSIL DUGONGIDAE (MAMMALIA, SIRENIA) FROM THE PARANÁ FORMATION (LATE MIOCENE) OF ENTRE RÍOS PROVINCE, ARGENTINA

Abstract. Fossil sirenians are well known from the Western Atlantic and Caribbean (WAC) region. Neogene records from the Atlantic coast of South America, although scarce, seem to reflect a similar taxonomic composition to its northern contemporaries. Fossil sirenians from Argentina are known from the late Miocene Paraná and Ituzaingó formations in Entre Ríos Province. An upper third molar housed in the Museo de Paleontología de la Universidad Nacional de Córdoba (CORD-PZ 4301), from the Paraná Formation, was originally described and assigned to the dugongid genus Metaxytherium Christol. Subsequent workers suggested it could instead belong to the dugongid genus Dioplotherium Cope, a designation that we confirm upon examination of the material. Additionally, we describe new sirenian remains from the Paraná Formation, consisting of two incomplete maxillae with teeth, belonging to one individual, deposited at the Museo de Ciencias Naturales de Paraná (MASP 373). This specimen shows similarities with species of Metaxytherium from the northern WAC. The Paraná Formation sirenians represent the southernmost occurrences of these two genera, and the geologically youngest occurrence of dugongids in the southern WAC. Dioplotherium and Metaxytherium also occur in the early Miocene of northern Brazil. The presence of these taxa as far south as Entre Ríos latitude suggests two possible dispersal routes: (1) across a marginal connection between a southern arm of the Amazonian Sea and the “Paranense Sea”; (2) along the Brazilian coast. Lastly, the occurrence of dugongids, which feed mainly on seagrasses, indicates that these marine angiosperms were present in the region as well.

A Taxonomic and Biogeographic Review of the Fossil Tapirs from Bolivia

Fossil remains of South American tapirs are often fragmentary and scarce compared with those of other mammals that entered South America during the “Great American Biotic Interchange”. Here, we review and add to the Pleistocene tapir remains from the Tarija Valley (Bolivia), and provide a taxonomic re-evaluation of Tapirus tarijensis. T. tarijensis was a large-sized animal, approximating the size of the living Malaysian T. indicus and the extinct North American T. haysii. The geographical distribution of Pleistocene records of Tapirus in South America indicates that T. tarijensis was the only known species inhabiting the Tarija Valley during this time.