Eutherian tarsals from the late Paleocene of Brazil. American Museum novitates ; no. 2761

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New York, N.Y. : American Museum of Natural History
"Disassociated eutherian proximal tarsals (astragalus, calcaneum) from Riochican (late Paleocene) fissure fills near São José de Itaboraí, Rio de Janeiro, Brazil, are described and, where feasible, are assigned to dental species from that locality, based on predicted morphology, relative size, and relative abundance. Two cingulate xenarthrans are present; one is probably a dasypodid, whereas the other may pertain to the Glyptodontidae. Ankle specializations of Carodnia vierai are unlike those of astrapotheres and Dinocerata, but similar to those of Pyrotherium and suggest reference to the Pyrotheria; Tetragonostylops apthomasi is pedally a primitive astrapothere. Notoungulate tarsals from Itaboraí, referred to Camargomendesia pristina (Henricosborniidae) and Colbertia magellanica (?Oldfieldthomasiidae), are of generalized aspect within the order, and represent a primitive morphotype from which later notoungulate families diverged. Litoptern tarsals are assigned to three species, Anisolambda prodromus, Ernestokokenia parayirunhor, and a new form; astragali and calcanea of 'condylarth' aspect are referred to Lamegoia conodonta, Victorlemoinea prototypica, and Ernestokokenia protocenica. The fact that some dentally primitive taxa (including a supposed congener of a dental and tarsal condylarth) bear the diagnostic litoptern ankle specializations, whereas others, including an advanced and dentally litoptern-like form do not, heightens the problem of distinguishing the two groups as currently recognized, and indicates that the fundamental specializations of the Litopterna are postcranial, not dental. Victorlemoinea, heretofore considered a macraucheniid litoptern but probably pertaining to the new family, Sparnotheriodontidae, shares derived pedal characters with the didolodonts; among the didolodonts, Ernestokokenia protocenica, Lamegoia conodonta, and ?Didolodus sp. seem to form a natural (monophyletic) group definable by tarsal features"--P. [1].
31 p. : ill. ; 26 cm.
Includes bibliographical references (p. 28-31).