Small wonders The phylogenetics of highly modified micro-echinoids in the genus Echinocyamus

Meeting Abstract

P3.192  Friday, Jan. 6  Small wonders: The phylogenetics of highly modified micro-echinoids in the genus Echinocyamus MARKELLO, K*; MOOI, R; San Francisco State University; California Academy of Sciences, San Francisco

Echinocyamus is a genus of approximately 15-20 species of micro-echinoids in the family Fibulariidae, colloquially called sea peas. These diminutive irregular sea urchins are distributed globally with representatives in all but one of the major oceans, and they exhibit a wide bathymetric range. Despite the abundance of some species, little is known of their biology and ecology. Taxonomic rivalries, inadequate data-collecting, and the urchins’ small size have resulted in several invalid and poorly defined species. This study provides the first detailed, species-level phylogenetic analysis of Echinocyamus, revising the genus to clarify dubious species. Unfortunately, material of nearly all known taxa is unsuited for molecular analyses. For the cladistic analysis, we collected morphological data from 18 species, and one new species from the Philippines was recognized. Morphological characters included petaloid shape, number of pores in each petaloid, test shape, and relative sizes of specialized pores, the mouth, and periproct. Phylogenetic analysis using parsimony allows us to infer the first-ever tree for the genus, and to map characteristics of the group to elucidate the major events in its evolution. We can also highlight specific features of the biogeography and bathymetric distribution of a widespread genus of very unusual micro-echinoids. By comparing this genus with its sister genus Fibularia and more distantly related Fibulariella, we hope to gain insight into the evolution of miniaturization in urchins.

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