Earth and Atmospheric Sciences, Department of
Date of this Version
7-30-2004
Abstract
New specimens of Palaeoryctes punctatus from the middle Clarkforkian of the Clarks Fork Basin include a left dentary preserving the crowns of I1-C1, P3, and M1-2, with alveoli for P2, P4, and M3. The lower dental formula, previously unknown for this species, is 3.1.3.3. A maxillary fragment preserves the crowns of a broken P4, complete M1, and a broken M2. Specimens previously referred to Palaeoryctes cf. P. punctatus and cf. Palaeoryctes sp. from the late Tiffanian are morphologically distinct and here included in a new species, Palaeoryctes jepseni. The holotype of P. jepseni is from Y2K Quarry, and additional specimens are known from Divide, Princeton, and Schaff quarries.
We describe a new genus and species, Ottoryctes winkleri, from the middle Wasatchian of the Bighorn Basin. The holotype includes nearly complete upper and lower dentitions, with a dental formula of 3.1.3.3 /3.1.3.3. Ottoryctes winkleri is similar to the earlier Eocene Eoryctes melanus in having ossified tubes marking the course of the stapedial and promontory branches of the internal carotid artery through the middle ear, rather than the smooth promontory found in Paleocene Palaeoryctes puercensis. O. winkleri differs from E. melanus in the structure of P4, in lower molar shape, and in being larger. The body weight of O. winkleri was about 80 grams, estimated from cranial length (ca. 36 mm), which is about 55% greater than the weight estimated for E. melanus.
The phylogeny of palaeoryctines can be approached stratophenetically, cladistically, and stratocladistically. Our cladistic analysis of seven North American palaeoryctine species using 32 morphological characteristics yielded four equally parsimonious cladograms. A stratocladistic analysis of the same morphological data yielded a better-resolved phylogeny with two overall most-parsimonious phylogenetic trees associated with a single cladogram. This result, which is more congruent with a traditional stratophenetic interpretation, suggests that Palaeoryctes jepseni from the late Tiffanian gave rise to Palaeoryctes punctatus in the latest Tiffanian or earliest Clarkforkian, and that P. punctatus gave rise in tum to a more derived Eoryctes-Ottoryctes clade in the latest Clarkforkian or early Wasatchian.
Comments
Published in Contributions from the Museum of Paleontology, University of Michigan (July 30, 2004) 31(5): 119-154. Copyright 2004, the University of Michigan. Used by permission.