The peristomial plates of ophiuroids (Echinodermata: Ophiuroidea) highlight an incongruence between morphology and proposed phylogenies
Fig 1
Introduction to the ophiuroid interbrachial frame.
Scanning electron micrographs of whole interbrachial frames and their isolated skeletal components of (A) Ophiacantha vivipara, (B) Ophiura lymani, (C) Amphiura eugeniae and (D) Ophioplocus januarii. (a) Whole interbrachial frame (aboral side). Arrows: green, tooth; yellow, dental plate; blue, oral plate; red, peristomial plate. White arrowhead (in Da), advertebral groove. (b) Dental plate (proximal side, aboral end at top). Arrowhead, tooth socket. (c) Tooth. Arrowhead, cap of imperforate (A. eugeniae) or more densely fenestrated (O. januarii) stereom. (d) Oral plate (adradial side, aboral end at top). Arrow (in Ad), neural groove; white arrowhead, adradial articular area; red arrowhead, advertebral groove (showing attachment area of distal radial ligament); asterisk, adradial muscle attachment area. (e) Oral plate (abradial side, aboral end at top). Arrow (in Ae), neural groove; arrowhead, interruption of differentiated stereom associated with bursal diverticulum; asterisk, abradial muscle attachment area. Scalebars: 2 mm (Aa, Ba, Ca, Da); 0.5 mm (Ad,e, Bb-e, Db-e); 0.2 mm (Ab,c, Bc, Cb-e).