New Mexico Geological Society Annual Spring Meeting — Abstracts

Three species of Coryphodon (Mammalia. Pantodonta) are present in the Regina Member of the San Jose Formation: C. simus (Cope, 1874), C. molestus (=C. lomas (Cope, 1874), =C. elephantopus (Cope, 1874), =C. latidens (Cope, 1875), =C. cuspidatus (Cope, 1875), =C. obliquus Cope, 1877, =C. curvicristis Cope, 1882, =C. wortmani Osborn, 1898) and C. lobatus Cope, 1877 (=C. anax Cope, 1881. =C. ventanus Osborn, 1898). C. simus is endemic to the San Juan Basin, but is a very advanced species of Coryphodon (M^1-3 lack postprotocristae, M₃ is bilophodont) that arguably is younger than early Wasatchian (Gray Bull biostratigraphic zone). In the Willwood Formation (Bighorn Basin, Wyoming), C. molestus first appears in the Bunophorus interval-zone and ranges through the upper Heptodon range-zone. In the Willwood Formation. C. lobatus first appears in the upper Haplomylus-Ectocion range-zone and also ranges through the upper Heptodon range-zone. Both C. molestus and C. lobatus also are found in the Lysite and Lost Cabin Members of the Wind River Formation, Wind River Basin,
Wyoming. This distribution of C. molestus and C. lobatus in Wyoming suggests that the Regina Member, at its oldest, is equivalent to the upper Gray Bull , biostratigraphic zone, but probably it is younger, either equivalent to the Lysite or Lost Cabin biostratigraphic zones. Earlier suggestions that the Regina Member is equivalent to the Lysite biostratigraphic zone thus are consistent with the Coryphodon species present.