The peristomial plates of ophiuroids (Echinodermata: Ophiuroidea) highlight an incongruence between morphology and proposed phylogenies - Fig 2

<p><b>Scanning electron micrographs showing aboral side of a single interbrachial frame unit (“jaw”) of (A) <i>Ophiacantha vivipara</i> (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0202046#pone.0202046.g001" target="_blank">Fig 1Aa</a>) and (B) <i>Ophioplocus januarii</i> (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0202046#pone.0202046.g001" target="_blank">Fig 1Da</a>).</b> aa, adradial articulation; dep, dental plate; do, distal part of oral plate; eim, external interradial muscle (between abradial sides of adjacent oral plates); L, maximum length of peristomial plate; po, proximal part of oral plate; ovm, orovertebral muscle (between oral plate and first vertebral ossicle); pep, peristomial plate; rm, radial muscle (between adradial sides of adjacent oral plates); t, tooth; arrowhead, ligament connecting peristomial plate to oral plate; W, maximum width of peristomial plate; asterisk, pore for water vascular canal that connects circumoral water vascular ring to buccal podia; red dots, lateral edges of aboral region of dental plate, the distance between which is the maximum transverse width, as defined herein. Scalebars: 1 mm.