Late Paleocene mammals
Late Paleocene (Tiffanian) mammal-bearing localities in superposition, from near Drumheller, Alberta
University of Alberta, Edmonton, Canada, 1996
Teresa Elise MacDonald
Abstract from a thesis for the degree of Master of Science (by research)
The Hand Hills West locality consists of two fossiliferous horizons in superposition, exposed along the same roadcut in southern Alberta. These two layers (here referred to as the Upper Level and Lower Level) are late Paleocene (Tiffanian) in age. The two horizons in superpositional relationship permit comparison between two faunal assemblages of different ages from one geographical area.
The recovery of Plesiadapis rex and Ectocion cedrus from the Upper Level indicates an age of middle Tiffanian (Ti3). This zone extends from 61.2 to 58.3 million years ago, for a duration of 2.9 million years. Diagnostic biostratigraphic evidence has not been recovered from the Lower Level. Based on palynostratigraphic and magnetostratigraphic evidence, the Lower Level represents an age of early Tiffanian (Ti2). This zone extends from 61.8 to 61.2 million years ago, for a duration of 0.6 million years. There is a disconformity below the Upper Level which precludes the determination of the precise amount of time between the two layers. Estimated sedimentation rates for the Paskapoo Formation suggest that the minimum amount of time represented between the two levels is approximately 293,000 years.
Fossils recovered from the Hand Hills West locality extend the geological time ranges of the plesiadapiform primates Elphidotarsius wightoni and Nannodectes gidleyi into the early Tiffanian, the pentacodontid Bisonalveus sp., cf. B. browni and the multituberculate Baiotomeus into the middle Tiffanian. The first record of the first upper incisor of Ignacius frugivorus and the first lower incisor of Nannodectes simpsoni may be represented from the Upper Level. The first record of the lower canine of Carpodaptes sp., cf. C. hazelae is represented from the Lower Level.
The faunal composition of the Upper Level and Lower Level are similar at the generic and often specific levels. The differences observed between the samples are due primarily to taphonomic and sampling bias.
The faunal composition of the Hand Hills West locality does not differ significantly from other localities in western Canada, and it reinforces the similarity between assemblages in northern North America and Eurasia, thus supporting the hypothesis of faunal interchange between these regions.