The Echinoid Directory

Key to the major clades of Camarodonta


1a. Ambulacral plate compounding in glyphocyphid style. Go to 2	1b. Ambulacral plate compounding in echinid style. Go to 4

2a. Primary tubercles perforate. Glyphocyphidae	2b. Primary tubercles always imperforate. Go to 3

3a. Apical disc monocyclic. Rachiosoma	3b. Apical disc hemicyclic. Zeuglopleuridae

4a. Test ornamented by pits or epistromal ridges (may be lost in adults) Go to 5	4b. Test unornamented; no pits or epistromal ridges at any stage. Go to 6

5a. Ornament consists of sharp-edged sutural pits. Temnopleuridae	5b. Ornament consists of raised epistroma or tuberculation with irregular depressions, some of which are sutural. Trigonocidaridae

6a. Apical disc monocyclic. Triplacidiids	6b. Apical disc hemicyclic to dicyclic. Go to 7

7a. Tubercles crenulate. Porosoma	7b. Tubercles non-crenulate. Go to 8

8a. Buccal notches deep and sharp. Toxopneustidae	8b. Buccal notches obsolete. Echinoida, Pseudechinus