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The Echinoid Directory

Family Echinocystitidae Gregory, 1897, p. 133

Diagnosis	Stem group echinoids with: test composed of ambulacral and interambulacral plates; plating thin and strongly imbricate throughout apical disc with single genital plate ambulacral zones quadriserial; pore-pairs small and undifferentiated internal perradial flanges on ambulacral plate enclosing the radial water vessel adorally interambulacra composed of up to 10 columns of thin, imbricate, polygonal plates no primary tubercle, but several small mamelonate secondary tubercles on interambulacral plates spines short and simple.
Range	Upper Silurian to Devonian, Europe.
Remarks	A more restricted usage of the family is applied here, since many of the taxa included here by Kier (1966) are treated as a separate clade, the Proterocidaridae. Proterocidaridae differ from Echinocystitidae in having large, circular, oral pore-pairs of very distinctive form. In addition their radial water vessel is generally not enclosed by perradial extensions of the ambulacral plates. Echinocystitidae are presumably a plesiomorphic sister group to Proterocidaridae, but a modern analysis of the problem is required. Kier, P. M. 1966. Noncidaroid Paleozoic echinoids. Pp. U298-U312 in Moore, R. C. (ed.) Treatise on Invertebrate Paleontology. University of Kansas Press & Geological Society of America, Boulder.

Diagnosis

Stem group echinoids with:

test composed of ambulacral and interambulacral plates; plating thin and strongly imbricate throughout
apical disc with single genital plate
ambulacral zones quadriserial; pore-pairs small and undifferentiated
internal perradial flanges on ambulacral plate enclosing the radial water vessel adorally
interambulacra composed of up to 10 columns of thin, imbricate, polygonal plates
no primary tubercle, but several small mamelonate secondary tubercles on interambulacral plates
spines short and simple.

Range

Upper Silurian to Devonian, Europe.

Remarks

A more restricted usage of the family is applied here, since many of the taxa included here by Kier (1966) are treated as a separate clade, the Proterocidaridae. Proterocidaridae differ from Echinocystitidae in having large, circular, oral pore-pairs of very distinctive form. In addition their radial water vessel is generally not enclosed by perradial extensions of the ambulacral plates. Echinocystitidae are presumably a plesiomorphic sister group to Proterocidaridae, but a modern analysis of the problem is required.

Kier, P. M. 1966. Noncidaroid Paleozoic echinoids. Pp. U298-U312 in Moore, R. C. (ed.) Treatise on Invertebrate Paleontology. University of Kansas Press & Geological Society of America, Boulder.