The Echinoid Directory

Key to the major clades of Camarodonta

1a. Ambulacral plate compounding in glyphocyphid style.
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1b. Ambulacral plate compounding in echinid style.
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2a. Primary tubercles perforate.
2b. Primary tubercles always imperforate.

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

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

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5a. Ornament consists of sharp-edged sutural pits.


5b. Ornament consists of raised epistroma or tuberculation with irregular depressions, some of which are sutural.


6a. Apical disc monocyclic.


6b. Apical disc hemicyclic to dicyclic.

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7a. Tubercles crenulate.


7b. Tubercles non-crenulate.

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8a. Buccal notches deep and sharp.


8b. Buccal notches obsolete.

Echinoida, Pseudechinus