Paper No. 11-3
Presentation Time: 1:40 PM
NEW CRINOIDS FROM THE "KIRKFIELD FAUNA" OF THE BOBCAYGEON AND VERULAM FORMATIONS (UPPER ORDOVICIAN), ONTARIO
The Upper Ordovician (lower Katian) Bobcaygeon and Verulam Formations from the Lake Simcoe region of Ontario contain a well-preserved echinoderm fauna, including diverse fossil crinoids. Although the diversity and abundance of crinoids in this assemblage has long been recognized, Springer's classic 1911 monograph describing collections from the Kirkfield locality remains the only taxonomic treatment of the fauna. Springer's report, however, was based on limited material and did not provide a comprehensive list of taxa in the assemblage. Recent extensive collection of crinoid material from the Bobcaygeon and Verulam Formations near Brechin, Ontario has produced an unprecedented number of exceptionally preserved crinoid specimens with arms, stems, and attachment structures intact. As the most exhaustive sample of crinoids from the region, this collection provides new material for re-assessing questionable taxonomic assignments and describing rare taxa that were previously unrecognized or unsampled.
Over thirty species are recognized from the Brechin collection, including two new genera and seven new species. The taxonomic composition of the Brechin fauna is somewhat atypical compared to most Katian crinoid assemblages. Although early Paleozoic crinoid faunas are commonly dominated by disparids, diplobathrid camerates, and hybocrinids, generic diversity of the Brechin assemblage is nearly uniform among cladids, camerates, and disparids; the cladid subclades Flexibilia and Hybocrinida are less taxonomically diverse. Similarly, in terms of relative abundance, cladids overwhelmingly dominate the fauna and are more than twice as abundant as specimens from all other crinoid clades combined.