An almost complete skeleton of a new Mesotheriidae (Notoungulata) from the late Miocene of Casira, Bolivia

CERDEÑO, E.; VERA, B.; SCHMIDT, G.; PUJOS, F.; MAMANI QUISPE, B.

JOURNAL OF SYSTEMATIC PALAEONTOLOGY

CAMBRIDGE UNIV PRESS

Lugar: London; Año: 2012 vol. 10 p. 341 - 360

1477-2019

A partial mesotheriine skeleton (Notoungulata, Mesotheriidae) from late Miocene Casira locality, southern Bolivia, is fully described and reinterpreted taxonomically. This specimen (MNHN-Bol-V-003724) was partially described previously without a taxonomic discussion, being considered as Plesiotypotherium sp. After comparison with other Bolivian, Argentinean, and Chilean mesotheres, werecognized a new species of the genus Plesiotypotherium Villarroel, P. casirense nov. sp., characterized by: nasals slightly enlarged posteriorly; zygomatic arch with strong antero-distal angle; zygomatic plate starting at the level of P4 and reaching the level of the anterior part of M3; lacrimal bony process; large infraorbital foramen; posterior border of the mandible very convex; P4 without lingual groove and with narrow and projected parastyle; M3 with simple third lobe; larger and more robust skeleton than other Plesiotypotherium species. Most postcranial elements are described in detail for the first time for Plesiotypotherium. The incomplete skull GB-KKL 740 from the same locality is also referred to the new taxon. P. casirense is the sister group of P. achirense Villarroel in the phylogenetic analysis, but the genus Plesiotypotherium appears as paraphyletic. The revised partial skull GB-ACH 100 from Achiri, Bolivia, which was labeled as Plesiotypotherium sp., does not belong to this genus, and it appears phylogenetically closer to Pseudotypotherium and Mesotherium. Plesiotypotherium casirense nov. sp. increases the known diversity of the Mesotheriidae in both the Miocene of Bolivia and the South American faunal context.