IANIGLA   20881
INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
A strange nothrotheriid ground sloth (Xenarthra, Megatherioidea) from Pomata-Ayte (Miocene-Pliocene transition, Bolivia)
Autor/es:
PUJOS, F.; DE IULIIS, G.; ADNET, S.; ANDRADE FLORES, R.; BILLET, G.; MAMANI QUISPE, B.; MARIVAUX, L.; PRÁMPARO, M.; ANTOINE, P.-O.
Lugar:
Mendoza
Reunión:
Congreso; 4th International Palaeontological Congress; 2014
Institución organizadora:
IPA
Resumen:
The
locality of Pomata-Ayte (Oruro department) was first reported by
Hoffstetter and colleagues at the end of the 1970s and partially
exploited by St-André in the 1990s. New collects have allowed
recovering a diverse mammalian assemblage dated between
5.97 ± 0.4 My and 5.42 ± 0.6 My (Montehermosan SALMA, Mio-Pliocene
transition). Among the taxa are two native ungulates, the litoptern
Macrauchenia
sp. and the toxodontid Posnanskytherium
cf. viscachanense,
a caviomorph rodent, a large phorusrhacoid bird, and six xenarthrans,
including three armored cingulates (the pampatheriine Plaina
sp., a glyptodontid, and a dasypodid) and three ground sloths (the
mylodontid Simomylodonuccasamamensis,
the large megatheriid Megatherium
(Megatherium)
altiplanicum,
and a small nothrotheriid). In the Pomata Ayte section, this
Montehermosan fauna is intercalated between a new early late Miocene
fauna with numerous mesotheriid notoungulates and caviomorph rodents
(K/Ar dating in progress) and a late Pleistocene fauna (?Lujanian
SALMA) with Macrauchenia
patachonica,
a gomphotheriid, a machairodontine felid, Megatherium
sp., and Glyptodon
sp. One of the most interesting Montehermosan mammals is the new
nothrotheriid. This small to medium-sized sloth is represented by a
complete mandible and several postcranials including humeri of three
distinct individuals. Mandibular dentition is strongly hypsodont
(Hypsodonty Index= 1.14). It has a small tricuspid caniniform (a
character unique among sloths) and three molariforms quadrate and
mesiodistally compressed with two transverse lophids (as in
megatheriines). There is neither diastema nor apicobasal sulci on
m1-m2 (although present on m3). The humerus is quite robust, with an
entepicondylar foramen, and a rather massive deltopectoral shelf. The
ulna is rectilinear in anterior view and the proximal articular
facets differ markedly from those of other nothrotheriids. The
calcaneus is massive and comparable in shape to that of Planops
and Thalassocnus.
A morphology-based phylogenetic analysis suggests that within the
Nothrotheriidae clade, this new taxon is a stem Nothrotheriini, being
more advanced over Pronothrotherium
and Mionothropus
from the late Miocene of Patagonia and Amazonia.