Life (and Death) Amongst Mammals in the Denver Basin, Colorado
EBERLE, Jaelyn J., Canadian Museum of Nature, P.O. Box 3443, Station D, Ottawa, ON K1P 6P4

Renewed prospecting and collecting of fossil vertebrates in the Denver Formation in the last few years has resulted in several significant discoveries of earliest Tertiary (i.e., Puercan) mammals. Notably, our collecting at South Table Mountain in August of 2000 uncovered five more mammalian specimens at Roland Brown’s original mammal locality (coined Brown’s Baioconodon site), including two taxa not previously known from the site - the multituberculate Catopsalis alexanderi and the “condylarth” Oxyclaenus. Both taxa corroborate initial correlations by others of the South Table Mountain Locality with the early Puercan-aged Alexander Locality, near Littleton. Additionally, the pectoral girdle of a very large (~200 lb) turtle, most probably a trionychid, as well as numerous crocodilian teeth and dermal skutes were recovered at South Table Mountain in 2000. Occurrence of mammal teeth that lack enamel, a diagnostic feature for teeth that have passed through the digestive tract of a crocodilian, suggests that at least two individuals of the woodchuck-sized Baioconodon denverensis met their demise at the jaws of a large crocodilian.

In strata of the Denver Formation east of Kiowa, two localities have produced middle or possibly late Puercan mammals, including Haploconus, Periptychus, cf. Promioclaenus, an as yet unidentified multituberculate, and the first and only taeniodont known from the Denver Basin. Both localities hold considerable potential, and will be the focus of intensive dry-screening operations in 2001.