HCNSO Student Theses and Dissertations

Defense Date

8-26-2015

Document Type

Dissertation

Degree Name

Ph.D. Oceanography/Marine Biology

First Advisor

Charles Messing

Second Advisor

Greg Rouse

Third Advisor

James Thomas

Fourth Advisor

Jose V. Lopez

Abstract

Superfamily Himerometroidea AH Clark, 1908 (Echinodermata: Crinoidea) (formerly Mariametroidea) is the second most speciose superfamily in order Comatulida. Although it includes some of the most common species on tropical western Pacific reefs, its phylogeny is poorly understood. Genus- to species-level taxa are currently distinguished by plastic morphological characters. We revised the superfamily from species- to family-levels using a combined morphological and molecular approach. A phylogeny using two nuclear and three mitochondrial markers recovered Colobometridae and Himerometridae as paraphyletic and Mariametridae and Zygometridae as polyphyletic. Within genus Himerometra (Himerometridae), sequence data and detailed morphological examinations of multiple specimens of H. magnipinna, H. martensi and H. robustipinna indicated that these three taxa are conspecific. A similar examination of specimens attributed on morphological grounds to the genera Dichrometra, Liparometra and Lamprometra (Mariametridae) revealed a lack of substantial enough sequence and morphological differences to maintain them as distinct genera. We have synonymized all three genera and redescribed four species under the senior name Dichrometra. Additional work is needed to more clearly establish characters that will diagnose clades across the superfamily. This study illustrates the importance of reevaluating classifications that incorporate ecophenotypically and ontogenetically variable characters.

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