New Mexico Geological Society Annual Spring Meeting — Abstracts

This is the first report of mammalian postcranial material from the Cretaceous of New Mexico. Quarry of the Fossil Forest has yielded a diverse mammal fauna based on isolated teeth and partial jaws; this is one of three mammal quarries in the Fossil Forest study area. A portion of the non multituberculate mammal fauna has been described elsewhere. Study of the multituberculate teeth continues. Recent work indicates that Quarry lies between the second and third forest levels in the Fossil Forest sequence (between the frrst and second tree stump levels) and is below the Campanian/Maastrichtian palynological boundary within the study area. During the 1984 field season, bulk matrix was collected in blocks and this was mechanically broken rather than bulk washed and screened. Among the material produced was the proximal portion of a left femur, 26 mm in length. The head of the femur is an almost complete sphere at the end of a long neck; they make a 60 degree angle with the shaft. No distinct foeva capitus is present. The greater trochanter is long and extends well beyond the head. The trochanteric fossa is lunate in outline, deep and present slightly proximally to the midline between the femoral neck and lesser trochanter. The interotrochanteric crest is prominent; the base of the lesser trochanter is present although the distal portions have been lost. It is possible to work out the details of the proximal musculature.

This femur is generally similar to the femoral material described by Sahni from the Judith River of Montana, although Sahni's material is poorly preserved. In overall morphology, the Fossil Forest femur is similar to the Paleocene femoral material of Eucosmodon described by Simpson and Elftman in 1928 and Granger and Simpson in 1929, but different in size and details of morphology. The same is also true for the Paleocene Ptilodus reconstruction presented by Jenkins and Krause in 1983. The Fossil Forest femur has been tentatively referred to Mesodma sp.