The Echinoid Directory

• Test small, ovoid, wide and low, widest posteriorly.
• Adapical surface low, flattened around apex. Adoral surface concave, strongly sunken towards peristome, flatter and angled upwards posteriorly.
• Apical system anterior; tetrabasal with three genital pores.
• Petals narrow, weakly developed, with small, rounded subequal pores; open distally.
• Periproct supramarginal, oval, oblique, slightly asymmetric in relation to longitudinal axis of test; midway between apical disc and posterior margin.
• "Pyrinoid" plating in ambulacra beyond petals.
• Peristome anterior; subpentagonal; wider than long.
• Phyllodes hardly developed, single pored; pores forming a single series towards the peristome in each half column,
• No buccal pores,
• Tubercles perforate, weakly crenulate; spines short with blunt rounded tip,

Lower Miocene to Recent, Australia and New Zealand,

Porterpygus kieri Baker, 1983, p. 164, by original designation.

• P. kieri Baker, 1983; Recent, Three Kings Islands, New Zealand,
• P. devlinensis Holmes, 1999; Lower Miocene, Australia,

Irregularia; Cassiduloida; Apatopygidae,

Presumed monophyletic,

Many of the characters used to differentiate this genus from Apatopygus are size dependent, however, the number of genital pores (three in Porterpygus, four in Apatopygus) provides a simple differential character.

Porterpygus is distinguished from Nucleopygus by the presence of pyrinoid plating in the ambulacra beyond the petals.

A. N. Baker. 1983. A new apatopygid echinoid genus from New Zealand (Echinodermata: Cassiduloida). National Museum of New Zealand Records, 2: (15), 164-173.

F. C. Holmes. 1999. Australian Tertiary Apatopygidae (Echinoidea). Proceedings of the Royal Society of Victoria 111, 51-70.