10th North American Paleontological Convention

10th North American Paleontological Convention
Date: 15-18 February 2014
Place: Gainesville, Florida

PRESENTATIONS and ABSTRACTS

1) Rhodes, K. and Baumiller T.K. What’s the worth of a taxon? Modern and fossil comatulid crinoids.

The fossil record of the comatulid crinoids is depauperate compared to the modern, with 10x higher generic diversity in the modern. Fossil and Recent comatulid species and genera are incommensurate, with fossil taxa largely described from a single element, the centrodorsal, while modern ones are described largely based on arms/pinnules, and more recently molecular data. To solve the problem of incommensurate data, we apply the same discrimination method, Bayesian finite mixture analysis on shape data, to the centrodorsals of modern and fossil taxa. Using this method, 4 subgroups are identified within the modern Promachocrinus kerguelensis/Florometra mawsoni species complex, which are divided into two species in two genera based on traditional taxonomy and as many as 7 clades based on genetic characters. Fossil Jaekelometra, traditionally placed into one or two species, is best described as a single group via the Bayesian analysis on shape of the centrodorsal. Several other modern taxa are best described as a single group based on centrodorsal characters. While question still remain about the relationship of modern and fossil taxa, these results show one group that is differentiated into more groups by centrodorsal shape than by traditional taxonomic characters. This suggests that the characters of the arms and pinnules used by neontologists need not always produce greater taxonomic resolution than those of the centrodorsal available to paleontologists, and that the differences in taxonomic practice alone are unlikely to be the sole explanation for the extremely high diversity of modern compared to fossil comatulids.

2) Syverson, V.J., Messing, C.G. and Baumiller, T.K. Reconstructing cyrtocrinid ecology and biology based on living population of Holopus andCyathidium.

The Cyrtocrinida (Crinoidea, Articulata) are the smallest and least well-known of living crinoid orders. Although they are known to have been common and highly diverse in the Mesozoic, only four extant species are known, all of which live cemented to hard substrates in deep water. Consequently, their biology and ecology are not very well understood, despite their interesting status as living representatives of a formerly important taxon and as living examples of the formerly common, but now rare, sessile crinoid life habit. Video footage of a hard-substrate continental slope community at Roatán, Islas de la Bahía, Honduras, has been obtained via submersible for two consecutive years (2012 and 2013). Hundreds to thousands of living individuals of the cyrtocrinids Holopus sp. and Cyathidium sp. (family Holopodidae) are recorded in the footage. Remains of dead individuals can also be discerned by the attachment structures still cemented to the substrate. This new source of information on living cyrtocrinids allows us to analyze the population structure of these populations using size-frequency distributions, live-dead counts, and spatial data, as well as recording changes in single individuals between the two years. We use these data to infer preferred orientations, reproduction and recruitment patterns, and life histories for
both taxa.