The Echinoid Directory

Key to the major clades of Scutelliformes

1a.Internal supports never more than simple radial struts; food grooves absent or rudimentary.

Stem group scutelliforms and paedomorphic derivatives of crown group taxa

1b.Internal supports developed as concentric bars, stellate patches or honeycomb mass after initial stages of growth; food grooves present.

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2a.Food grooves an unbranched perradial trunk that extends across the most adoral two or three pairs of ambulacral plates (arrow marks edge of basicoronal plate).

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2b.Food grooves bifurcating at outer edge of first post-basicoronal ambulacral plate.


3a.Five gonopores.


3b.Four gonopores.

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4a. Food grooves bifurcating at second post-basicoronal plate.


4b. food grooves simple or trifurcating at third post-basicoronal plate.