Fossil Sharks of the Rocky Mountains: Ctenacanthus and other Chondrichthyan Spines and Denticles

This talk was presented at the 2002 Annual Meeting of the Pacific Division of the American Association for the Advancement of Science at the Hawaii Preparatory Academy, Kameula, Hawaii, on June 15, 2002. The abstract follows:

Fossil Sharks of the Rocky Mountains: Ctenacanthus and other Chondrichthyan Spines and Denticles. WAYNE M. ITANO, KAREN J. HOUCK, and MARTIN G. LOCKLEY (1995 Dartmouth Ave., Boulder, CO 80305; Dept. of Geography, Geology, and Environmental Science, University of Colorado, Denver, 80217). Chondrichthyan spines and dermal denticles are reported from the Middle Pennsylvanian Minturn Formation, Eagle County, Colorado. The most common element is a dorsal finspine referred to Ctenacanthus buttersi St. John and Worthen. The holotype and only previously figured specimen of C. buttersi, from the Pennsylvanian of Illinois, consists of the proximal half of a dorsal finspine. The Colorado specimens allow us to reconstruct the appearance of nearly the entire finspine. The finspine of C. buttersi shows an unusual combination of features, since the surface ornament, consisting of numerous, finely denticulated longitudinal ribs, is typical of ctenacanthiform sharks, while the posterior face is convex, a feature normally associated with another group of sharks, the hybodonts. Less common remains from the Minturn Formation include a dorsal finspine referred to Acondylacanthus nuperus St. John and Worthen, another dorsal finspine close to "Ctenacanthus" furicarinatus Newberry, a spine fragment probably referrable to Physonemus sp., and two large-noded dorsal finspines probably referrable to two different species of Bythiacanthus. Dermal denticles are referred to Petrodus patelliformis M’Coy. All of these finds represent extensions of the known geographic ranges to the southern Rocky Mountain region of these taxa, most of which were originally described from the mid-continent of North America. Ctenacanthus buttersi finspines and some large cladodont teeth, referred to "Cladodus" occidentalis Leidy, may belong to the same species. This conjecture is based mainly on the relative abundances of chondrichthyan teeth found at the same locality.

The slides from the talk are available as a 1.5 MB PDF file.

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