Colhuehuapian Astrapotheriids (Mammalia) from Gran Barranca south of Lake Colhue Huapi

KRAMARZ, A.; BOND, M.

The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic

Cambridge University Press

Lugar: Cambridge; Año: 2010; p. 182 - 192

In this contribution the taxonomic status of the numerousastrapothere species described by Ameghino for hisColpodon beds (Colhuehuapian) are revised, and thediversity and distribution of the Colhuehuapian astrapotheresare examined in light of new and more completematerial, and with more precise stratigraphic information.The new material discussed here comes from theLower Fossil Zone of the Colhue-Huapi Member of theSarmiento Formation; previously described material isknown of presumed to have come from this same leveland belongs to the Colhuehuapian SALMA, the Colpodonbeds of Ameghino. The Lower Fossil Zone is dated toearly Miocene, about 20 Ma from radiometric and magneticpolarity data (Re´ et al. Chapter 4, this book).Our revision reveals the certain presence of threespecies: Astrapotherium? ruderarium (Ameghino 1902),Parastrapotherium symmetrum (Ameghino 1902), andParastrapotherium martiale Ameghino 1901 (the latteralso known from the older Deseadan SALMA). Parastrapotheriumherculeum may represent a fourth very largespecies but the type material of Ameghino (1889), supposedto come from Colhuehuapian beds, cannot belocated, and no available specimen can be certainlyreferred to it. Finally, a single upper canine seems torepresent a fifth unnamed species, perhaps a uruguaytheriineastrapothere. Examination of old and new collectionssuggests that Astrapothericulus is not recorded at theselevels, although the genus does occur at otherColhuehuapianlocalities.The following names are brought into synonymy withAstrapotherium? ruderarium:Parastrapotherium paucum Ameghino 1902Parastrapotherium crassum Ameghino 1902 (partim)Astrapothericulus minusculus Ameghino 1902Astrapothericulus laevisculus Ameghino 1902Astrapotherium triangulidens Ameghino 1902Prochalicotherium patagonicum Ameghino 1902Astrapotherium? ruderarium is the only recognizedspecies of Astrapotherium in the Colhuehuapian Age.Astrapotherium? ruderarium also is the most abundantastrapothere in Colhuehuapian levels of Gran Barranca.