The Echinoid Directory

• Test small (less than 5 mm), ovate and flattened in profile with rounded margin.
• Apical disc central with five gonopores and a single hydropore.
• Sexually dimorphic with females having adapical zone deeply sunken.
• Petals short and converging distally; forming stellate pattern.
• Ambulacral and interambulacral zones of similar width at ambitus.
• Pores extend onto interambulacral plates.
• Interambulacral columns end in single element adapically.
• Food grooves absent.
• Periproct inframarginal, opening between first and second pair of post-basicoronal plates.
• Interambulacra continuous adorally. Basicoronal interambulacral plates not projecting. First paired interambulacral plates elongate.
• Internal partitions consisting of 10 L-shaped struts plus a few concentric supports extending from radial bars.

Middle Eocene, Georgia, USA.

Pentedium curator Kier, 1967, p. 990, by original designation.

• Only the type species.

Clypeasteroida; Scutellina; Laganiformes; Laganidae; ?Neolaganinae.

Monotypic.

Males are very similar to small Durhamella but Durhamella never shows sexual dimorphism. The petals are probably composed of simple plates only (plating is not seen in any specimen) given the small size of individuals. Its branching internal supports show it to be a member of the Laganidae, but its small size makes certain placement in either the Laganinae or Neolaganinae impossible. Tetradialla is identical in all respects except that it has four gonopores rather than five.

P. M. Kier 1967. Sexual dimorphism in an Eocene echinoid. Journal of Paleontology 41, 988-993.