Platyasterida

Platyasterida

[¦plad·ē·a′ster·ə·də]
(invertebrate zoology)
An order of Asteroidea in which traces of metapinnules persist, the ossicles of the arm skeleton being arranged in two growth gradient systems.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.