Evolution and Systematics of Holothuroidea (Echinodermata)

Holothuroids are among the most poorly studied echinoderms. Probably only half of reef-associated species have been described, while poorly understood species complexes and nonmonophyletic higher taxa abound. We have long been engaged in a major collaborative effort to estimate the phylogenetic relationships of holothuroids, primarily within the aspidochirote family Holothuriidae, which has diversified extensively onto coral reefs. We also sought to resolve the major deep branches of holothuroid relationships. The phylogeny suggests that sea cucumbers have survived the end-Permian mass extinction much better than the other echinoderm classes, though at least one group similarly experienced a large radiation in the early Mesozoic. Based on this work, we are beginning to revise the taxonomy of Holothuriidae, as well as the entire class at subclass and ordinal levels. Below is a painting by Emily Damstra from Kerr (2003 in Grzimek's Animal Life Encyclopedia Gale Publ NY) of Pelagothuria natatrix, a deepwater holothuroid and the only completely pelagic echinoderm.

Copyright © 2003 Emily Damstra