The Echinoid Directory

• Test relatively thick and depressed.
• Apical disc slightly less than half the test diameter; dicyclic with ocular plates strongly insert. Genital plates all similar in size. All plates densely covered in uniform granules.
• Interambulacra with up to 10 plates in a series. Primary tubercles perforate and non-crenulate. Areoles circular and separated; weakly incised.
• Scrobicular tubercles differentiated. Extrascrobicular zones relatively narrow with dense and unusually fine granulation.
• Ambulacra weakly sinuous. Pore zones incised. Pore-pairs subconjugate and with relatively narrow interporal partition. Perradial zone with marginal series of primary tubercles and inner series of one or two secondary tubercles per plate.
• No naked zones or pits.
• Peristome similar in size to the apical disc with ambulacral plates uniserially arranged in each column. Interradial plating present but not reaching the mouth.
• Primary spines stout and rather short. Collar moderately long. Shaft ornamented with coarse blade-like thorns irregularly arranged proximally and tending to form lines distally.
• Secondary spines outside scrobicular circles small and scale-like; strongly adpressed.

Miocene to Recent, Indo Pacific.

Chondrocidaris gigantea Agassiz, 1863, p. 18, by original designation.

• C. gigantea Agassiz, 1863; Recent, Pacific.
• C. brevispina Clark, 1925; Recent, Pacific (Indonesia, northern Australia, Loyalty Islands, Samoa).
• C. problepteryx Clark, 1945; (?Upper) Miocene, Fiji.
• C. compta (Philip, 1964); Miocene, Australia.

Cidaroida, Cidaridae, Cidarinae.

Presumed monophyletic.

This genus is immediately distinguished by its small scale-like secondary spines and its coarse and distinctively ornamented primary spines. Menocidaris has a very similar spine morphology, but was distinguishing by Philip (1964) because of its lack of extrascrobicular zones and its non-conjugate pore-pairs. Both characters probably reflect the small size of the specimens of M. compta, and the two genera are probably best synonymized. Philip provides a discussion of the fossil record of Chondrocidaris-type spines.

Agassiz, A. A. 1863. List of echinoderms sent to different institutions in exchange for other specimens. Bulletin of the Museum of Comparative Zoology, Harvard College, 1 (2), 17-28.

Mortensen, T. 1928. A monograph of the Echinoidea. 1, Cidaroidea. C. A. Reitzel, Copenhagen.

Philip, G. M. 1964. The Tertiary echinoids of South-East Australia. Proceedings of the Royal Society of Victoria 77, 433-477, pls 58-67.