Brittlestars with a bite: a new kind of pedicellaria in echinoderms.

Echinoderm pedicellariae are groups of specialized opposable spines (valves) that articulate on a baseplate. The valves of a pedicellaria act together to grasp items for prey capture, surface cleaning, or defense. Pedicellariae have long been known to occur in sea urchins and seastars, and many types for different functions have been described. Here we describe a type of pedicellaria in basketstars and snakestars in the euryalid family Gorgonocephalidae. Valves of gorgonocephalous pedicellariae have been described and illustrated as independent "hooklets" since the 1800s. Aside from one illustration in 1930, baseplates have been illustrated only since the 1980s, after the advent of the scanning electron microscope. The structure, arrangement, and operation of valves on baseplates warrant their recognition as a pedicellaria, analogous to those of sea urchins and seastars. The gorgonocephalous pedicellaria is a multi-valved, unstalked, crossed pedicellaria. It is described and illustrated here with recommended morphological terminology to facilitate future studies on biomechanics, histology, paleontology, and phylogenetics. [ABSTRACT FROM AUTHOR]