Oldfieldthomasiidae

Left: Reconstruction of the skull of Oldfieldthomasia debilitata in lateral view.  Right: Left upper P1-M3 (above) and left lower p4-m3 (below) of Oldfieldthomasia debilitata in occlusal view.  Both figures are from Simpson (1967).

Oldfieldthomasiids, like henricosborniids and notostylopids, are most common in Paleocene and Eocene faunas.  They are also abundant and diverse in the peculiar Divisadero Largo fauna of Mendoza, Argentina, which may be late Eocene or Oligocene in age.  Some excellent fossils of Oldfieldthomasia have been found and have permitted a better understanding of typothere anatomy; Simpson (1936) was able to describe in detail the cranial anatomy of Oldfieldthomasia using a set of fifty-five serial sections, each 4 mm thick, cut parallel to the long axis of the skull.  In most respects, oldfieldthomasiids are of a generalized typothere form and are lack derived character states permitting them to be assigned to other, better defined, families. Representative Taxa:   Order Notoungulata     Suborder Typotheria       Family Oldfieldthomasiidae: Oldfieldthomasia, Kibenikhoria, Maxschlosseria, Ultrapithecus,                                                    Tsamnichoria, Brachystephanus