28.3 Jan. 5 An atypical type taxon: Phylogenetics and biology of the echinid Echinoidea COX, L.N.*; MOOI, R.; Auburn Univ., Alabama; California Acad. Sciences, San Francisco email@example.com
The Echinidae Gray, 1825 is a well-known, widely distributed group of sea urchins. Their ubiquity in the northern Atlantic, particularly the genus Echinus, gave rise to the earliest concepts of the Echinoidea itself. The echinids live in a wide range of habitats from the deep-sea to the intertidal. In spite of the familiarity of some echinids, their systematics remain very poorly known. There have been no species-level phylogenies of this group, nor have there been any attempts to support the monophyly of its constituent genera. We performed a phylogenetic analysis using 40 morphological characters assessed from nearly all the species of Echinus Linnaeus, 1758; Gracilechinus Fell & Pawson, 1965; Dermechinus Mortensen, 1942; Sterechinus Koehler, 1901; Polyechinus Mortensen, 1942; Stirechinus Desor, 1856; plus putative outgroups Psammechinus Agassiz and Desor, 1846; Paracentrotus Mortensen, 1903; Parechinus Mortensen, 1903; Loxechinus Desor, 1856; and Strongylocentrotus Brandt, 1835. The analysis supports monophyly of Sterechinus, but not of either Echinus or Gracilechinus. The validity of Gracilechinus is questionable given that it is based on a single, homoplastic feature. The bizarre, cucumber-shaped echinid, Dermechinus, is more closely related to Sterechinus, forming with it an exclusively Antarctic clade. The monophyly of the Echininae Mortensen, 1903 is supported, but there are no non-homoplastic characters distinguishing it from the Parechininae Mortensen, 1903. The results of this study suggest the need for radical taxonomic revision, in conjunction with molecular studies. However, with this first phylogeny, aspects of the biology, bathymetry, and biogeography of the echinids can be explored.