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Libro de resúmenes de la RCAPA 2024 - The giant mylodontid ground sloth Ocnotherium giganteum (Xenarthra, Folivora) from the Late Pleistocene of brazilian caves
Congreso
Autoría:
Pujos, F. ; De Iuliis, G. ; BOSCAINI, ALBERTO ; Iurino, Dawid A. ; Strauss, André ; Vilaboim, L. ; Cartelle, CástorFecha:
2024Editorial y Lugar de Edición:
Publicación Electrónica de la Asociación Paleontológica ArgentinaResumen *
Ground sloths are among the most distinctive and remarkable representatives of extinct South America mammalian faunas. Folivorans are generally grouped into four or five clades, including Mylodontidae, which encompasses famous genera such as Mylodon and Glossotherium. In 1839, based on isolated teeth from Lagoa Santa Cave in Brazil, the Danish naturalist P. W. Lund established the species Ocnotherium giganteum. Several recently recovered remains, deposited at the Museu de Ciências Naturais da Pontifícia Universidade Católica de Minas Gerais, Belo Horizonte, Brazil, including an almost complete specimen with skull and mandible and a second specimen with all its teeth, provide new data on this Late Pleistocene giant sloth. Ocnotherium exhibits unique characteristics that combine cranio-mandibular features of Mylodontinae, postcranial features of Lestodontinae, and distinctive dental traits. The digital brain endocast strongly resembles that of Glossotherium and differs from those of Catonyx and modern sloth genera. The inner ear of Ocnotherium is markedly reduced relative to skull size. The bony labyrinth is similar to that of other ground sloths, with thin and elongated semicircular canals. Paranasal pneumaticity is highly developed, with the posterior two-thirds of the skull being extensively pneumatized. The skull is larger than that of all Mylodontidae except Lestodon and exhibits a second medial glenoid fossa, similar to Catonyx tarijensis. The dental formula is Cf/cf– Mf1–4/mf1–3, typical of Mylodontidae. The dentition differs in lacking a diastema between the two most anterior teeth. However, very long diastema is present between Mf1 and Mf2, and Mf1 is strongly compressed transversely, lacking apicobasal sulci. Mf1 is the narrowest and most strongly curved upper tooth; it arches distally across the diastema. The proximodistal axis of the humerus in Ocnotherium is straight in anterior view. The ulna and radius are extremely short and massive, with strong muscular insertions. The manus is pentadactyl, featuring three clawed medial functional digits. The L-shaped metacarpal-carpal complex consists of fused trapezium, McI, and first phalanx. The femur is rectangular and elongated, lacking torsion. The angle between the odontoid and discoid facets of the astragalus is close to 90°, similar to lestodontines. The foot exhibits at least four digits. The results of a cladistic analysis based on an ingroup of 33 sloth species and 383 characters suggest that Ocnotherium is a member of Mylodontinae. Ocnotherium retains several primitive features and is also supported by 22 autapomorphies. It diverged after the Neogene taxa Pleurolestodon and Simomylodon, but earlier than other Pleistocene forms such as Mylodon and Paramylodon. Información suministrada por el agente en SIGEVAPalabras Clave
MylodontidaeSlothBrazilXenarthra