“There has been a curious reluctance among investigators in regard to attempting work upon these animals (comatulids). But on the whole this is probably a fortunate circumstance, for few organisms are so baffling and so difficult a systematic analysis and few have so well resisted the efforts of able zoologists properly to understand them.” - Austin Hobart Clark, 1915


A Revision of the Superfamily Mariametroidea with an Emphasis on Phylogeography

Crinoids (Phylum: Echinodermata) are filter feeders that can be found from the sublittoral all the way down to the abyssal plain. With a body plan composed of many ossicles, crinoids fossilize well and can be found as far back as the Ordovician. Despite the prominence of unstalked crinoids (comatulids) on shallow, Pacific Ocean reefs the phylogeny of this group is poorly understood.

It is widely accepted that the phylogeny of shallow water crinoids, in particular comatulids of the super family Mariametroidea, needs revision. My work is directed at resolving the current phylogenic conflicts within this superfamily. The methodology involves a combination of both morphological and molecular techniques.

My analysis of the phylogeography of several genera within the Mariametroids is part of a larger effort to look at genetic variation among echinoderms across their known ranges. Asteroids and Echinods have been used in phylogeography studies across the Indo-Pacific but comatulids have not yet been examined. My research is directed at filling that void.

Most recent work: Synonymizing H. magnipinna and H. robustipinna, and evaluating genera descriptions within the family Mariametridae - namely Stephanometra and Mariametra.

(My work is in collaboration with other researchers as part of the NSF-funded Echinoderm Tree of Life project.)
Molecular techniques:

Working with colleagues from Scripps Institute of Oceanography in San Diego, CA a wide range of taxa have been sampled and sequenced. Looking at nuclear (16s and 28s) and mitochondrial (CO1) sequences new phylogenies have been proposed. Interestingly, the current molecular phylogenies are contrasting with the original phylogenies based on morphological characters. Such results reveal that more taxa need to be sampled and our current diagnostic morphological characters need to be reevaluated. 		 
Morphological techniques:

The main emphasis of my work on comatulids involves analysis of morphological characteristics. Comparing a wide range of descriptive characters can elucidate relationships among closely allied families and genera. Such characters include relative size of oral pinnules, centrodorsal architecture, genital pinnules and branching patterns. More often than not, descrete measurements are not possible so dimension ratios are used. Examining the length/width ratio of certain ossicles can be very revealing to as far down as the species level.

Two methods used for morphology analysis are sketching using a camera lucida and image capture with a scanning electron microscopy (SEM).

In order to analyze a large number of taxa, several trips to the Smithsonian Natural History Museum Support Center have been made, and more will be made in the future.