The Echinoid Directory

• Test large, hemispherical, depressed below, domal above.
• Apical disc small, angular, plating hemicyclic with the two posterior ocular plates exsert. Periproct outline apparently smooth.
• Ambulacra straight; plating polygeminate, compound style not discernable but only single large element perradial of pore-zone and some pore-pairs on small, occluded plates. Pore-pairs undifferentiated; arranged in transverse arcs of about 8 pore-pairs above the ambitus, these arcs separated by a row of tubercles. Remaining arcuate beneath the ambitus with 6 pores to a plate. Adoral arrangement not seen.
• Up to 3 subequal primary tubercles to each compound plate plus two or three rows of smaller perradial granules on ambital and adapical plates.
• Interambulacral plates much wider than tall; with a row of up to 7 subequal tubercles on ambital and subambital plates. Above the ambitus only the four adradial tubercles remain leaving a wide interradial zone of horizontally aligned rows of granules. Primary tubercles are lost adapically with only a single tubercle on adapical plates.
• No naked interradial zone adapically.
• Tubercles imperforate and strongly crenulate.
• Peristome possibly relatively large.
• Spines unknown.
• Lantern unknown.

Latest Palaeocene - Lower Eocene, Pakistan.

Eurypneustes grandis Duncan & Sladen, 1882, p. 46, by original designation.  Holotype: Geological Survey of India 2504.

• Only the type species.

Euechinoidea, Camarodonta, unnamed family (triplacidiids).

Monophyletic

The type is just a fragment of the upper surface. A large and complete test is in the BMNH (illustrated above). The horizontal arcs of pore-pairs are found in only some taxa of Echinidea, and this taxon stands very distant from any of the other members included in this family. Although plate compounding style is not known, the coarsely crenulate tuberculation suggests affinities lie with the Temnopleuridea rather than the Echinidea.

Duncan, P. M. & Sladen, W. P. 1882. The fossil Echinoidea from the Ranikot Series of Nummulitic starat in western Sind. Memoirs of the Geological Survey of India, Palaeontologia Indica. Tertiary and Upper Cretaceous fossils from Western Sind, Series XIV, Vol. 1.3.