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TITLE: Dental variation and temporal change in early Eocene Hyopsodus (Mammalia, Condylarthra) from the Powder River Basin, Wyoming
AUTHOR: Frank P. Cuozzo
JOURNAL: PaleoBios
PUBLISHED: Oct 31, 2002
NOTES: 22(2)
ABSTRACT: This study investigates patterns of dental variation and temporal change in a sample of 627 stratigraphically con-trolled Hyopsodus specimens from the early Eocene of the Powder River Basin, Wyoming. Specimens studied span a stratigraphic interval of 140 meters of section, and represent a biostratigraphic range from the later Wa2 to early Wa3 faunal zones of the Wasarchian North American Land Mammal Age. Among the patterns observed is a distinct size increase early in Wa3, the uppermost of the six stratigraphic levels sampled, illustrated by the largest mean for 11 ol the 16 variables studied occurring at this top level. In addition, all variables (other than those which have several single specimen stratigraphic level samples) show a size increase between the latest Wa2 level and early Wa3. This pattern of increasing size early in Wa3 is seen in other mammals (e.g., Haplomylus and Apheliscus) in the Powder River Basin (Robinson 1986), and in Hyopsodus in other intermontane basins of North America, such as the Clark's Fork Basin (Gingcrich 1994). This size increase corresponds to the general (relative) cooling trend that occurred during the transition from the early to middle Wasarchian in North America documented in the Bighorn Basin (e.g., Bown et al. 1994, Wing 1998, Wing et al. 2000). Although not focused on taxonomy, a cursory morphological analysis suggests the presence of two distinct Hyopsodus lineages throughout the stratigraphic interval sampled, as does the amount of metric variation seen for a number of tooth positions at different stratigraphic levels (CV > 10 in 19 of 86 total measurements). The indication of two distinct Hyopsodus lineages provides support for an earlier report for the Powder River Basin (Robinson 1986), and corresponds to the general pattern of Hyopsodus diversity seen throughout western North America during the early Eocene (e.g., Redline 1997).
COLLECTION: PaleoBios Archive Public
ID: 146

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