The Echinoid Directory

• Test small and ovate; anterior notch not developed.
• Apical system ethmolytic, with four gonopores.
• Strong sexual dimorphism, with females having entire adapical region deeply invaginated.
• Anterior ambulacrum with small pentagonal plates; pores rudimentary.
• Ambulacral petals flush with test and poorly defined; anterior ambulacrum narrow with small simple pores.
• Paired ambulacra sub-petaloid with only slightly enlarged pore-pairs. In anterior pair the pore-pairs in the anterior column are only present distally.
• Adapical surface with uniform small, scattered tubercles and granules.
• Labrum short, not extending past the neighbouring first ambulacral plates.
• Sternal plates bowed and fully tuberculate. Episternal plates strongly pinched posteriorly.
• Subanal fasciole well-developed; shield-shaped.
• Three ambulacral plates and two pore-pairs of each posterior ambulacra within fasciole.

Lower to Middle Miocene, Australia.

Peraspatangus brevis Philip & Foster, 1971, p. 690; by original designation.

• P. brevis (Philip & Foster, 1971); Lower Miocene, Victoria, Australia.
• P. depressus (Philip & Foster, 1971); Middle Miocene, Victoria, Australia.

Spatangoida, Micrasterina, ?Brissidae.

Monophyletic.

The small size explains the rudimentary nature of the petals. Plastron structure, especially the pinched episternal plates and wide labral plate, suggests affiliation with Nacospatangus rather than spatangids.

Philip, G. M. & Foster, R. J. 1971. Marsupiate Tertiary echinoids from south-eastern Australia and their zoogeographic significance. Palaeontology 14, 666-695.