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Colhuehuapian Astrapotheriids (Mammalia) from Gran Barranca south of Lake Colhue Huapi
A.G. KRAMARZ AND M. BOND
The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic.
Cambridge University Press
Lugar: Cambridge,UK; Año: 2010; p. 182 - 192
ABSTRACT. In this contribution the taxonomic status of the numerous astrapotherespecies described by Ameghino for his Colpodon beds (Colhuehuapian) are revised, and thediversity and distribution of the Colhuehuapian astrapotheres are examined in light of newand more complete material, and with more confident stratigraphic information. Basedupon dental characters, only three nominal species are recognized: ?Astrapotherium?symmetrum Ameghino, 1902?, ?Astrapotherium herculeum Ameghino, 1899? (supposedlyColhuehuapian), and ?Parastrapotherium ruderarium Ameghino, 1902? (=Parastrapotherium paucum, Astrapothericulus minusculus, Astrapothericulus laevisculusand Astrapotherium triangulidens Ameghino, 1902). Parastrapotherium martiale Ameghino,1901 (previously described for the Deseadan SALMA) also occurs at these levels. A fifthunnamed species is allied to a new taxon recorded at the Early Miocene Cerro BanderaFormation (Neuquén Province, North Patagonia). Astrapotherium? symmetrum andAstrapotherium herculeum are transferred to Parastrapotherium. Parastrapotheriumruderarium shows a complex combination of dental characters, transitional in part betweenParastrapotherium holmbergi (Deseadan SALMA) on one hand, and Astrapotheriummagnum (Santacrucian SALMA) and Astrapothericulus iheringi (?Astrapothericulan beds?,late Early Miocene) on the other. This species is herein provisionally transferred to thegenus Astrapotherium by having higher crowned cheek teeth than in P. holmbergi, p3absent, p4 with labial flexid, ever growing upper canines and cingula present at the base ofthe labial fold of the upper premolars and at the base of the metaconid of the lower molars,as in A. magnum. However, it still retains three lower deciduous premolars, as in theOligocene astrapotheres. Though with similar size, it differs from Astrapothericulusiheringi by having cheek teeth with much more delicate basal cingula. Astrapotherium?ruderarium is largely the more abundant astrapothere in Colhuehuapian levels of GranBarranca. Examination of old and new collections suggests that Astrapothericulus is notrecorded at these levels, even if the genus positively occurs at other Colhuehuapianlocalities. If this assignation is confirmed, Astrapotherium? ruderarium would be the onlyrecognized species of Astrapotherium in the Colhuehuapian Age.