Fixed, free and fixed: the fickle phylogeny and fascinating ecology of extant Crinoidea
Charles G. MESSING
Oceanographic Center, Nova Southeastern University, Dania Beach, FL, USA
WEDNESDAY 19th September, 12pm
Neil Chalmers Science Seminar Room (DC.LG16)
Recent morphological, molecular and field research has substantially expanded and altered understanding of this least-known class of living echinoderms. New molecular phylogenies have confirmed some groups and upended the classification of others, e.g., some stalked taxa have apparently arisen from within the "unstalked" comatulid feather stars. Character analysis and taxonomy are both in for major overhauls. Field research is revealing often unexpected insights into crinoid biology, ecology and taphonomy, e.g., stalk growth rates of up to 17 cm/y, predation by other echinoderms, and completely novel morphologies. Although recent work has eliminated many synonyms, the number of taxa has continued to increase, e.g., the number of species in one deep-sea family tripled in the last 15 years, while one 10-day submersible expedition in the Bahamas in 2009 added four new crinoid species, increasing the tropical western Atlantic fauna by 7%. One of these exhibits a feature previously unknown in any crinoid, living or fossil. Though placed within a known genus, its unique character, perhaps the result of a mutation or duplication in a genetic control switch, may represent the potential foundation of a new lineage and a wellspring of future crinoid diversification.
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