The Echinoid Directory

Phyllacanthus Brandt, 1835, p. 267

[=Leiocidaris Desor, 1855, p. 48, type species Cidarites imperialis Lamarck, 1816 ]

Diagnostic Features
  • Test thick.
  • Apical disc small; generally less than 40% test diameter. Plating dicyclic; densely covered in tubercles/spines. Genital plate 2 significantly larger than other genital plates.
  • Interambulacra with between 5 and 9 plates in a series. Primary tubercles perforate and non-crenulate; areoles incised. Scrobicular tubercles differentiated and separate, except immediately beside the peristome where they may be confluent. Extrascrobicular zones poorly developed and with heterogeneous tuberculation.
  • Ambulacra sinuate and moderately broad. Pore-pairs horizontal and well developed; the two pores widely separated and conjugate. Perradial tuberculation comprises a marginal primary and one or more slightly smaller inner secondaries.
  • Peristome large (larger than apical disc); ambulacral plates quadriserial in each zone. Interradial plates confined to outer part of peristomial membrane only.
  • Primary spines stout and weakly fusiform, tapering to a blunt point. Shaft ornamented by dense granules more or less regularly arranged, but not forming distinct ribs.
  • Secondary spines flat, scale-like and strongly adpressed.
Upper Oligocene to Recent, Indo-Pacific.
Name gender masculine
Cidarites (Phyllacanthus) dubia Brandt, 1835, p. 268, validated by International Commision of Zoological Nomenclature Opinion 208.
Species Included
  • P. dubius (Brandt, 1835); Recent, Bonin Islands.
  • P. imperialis (Lamarck, 1816); Lower Miocene-Recent, Indo-Pacific.
  • P. parvispinus Tenison Woods 1880; Recent, Australia.
  • P. longispinus Mortensen, 1918; Recent, Australia.
  • P. magnificus Clark, 1914; Recent, Australia.
  • P. irregularis Mortensen, 1928; Recent, Australia.
  • P. titan Fell, 1954; Upper Oligocene to Middle Miocene, New Zealand.
  • P. wellmanae Fell, 1954; Upper Miocene, New Zealand.
  • P. duncani Philip, 1963; Oligocene & Lower Miocene, Australia.
  • P. clarkii Chapman & Cudmore, 1934; Lower Miocene, Australia.
  • P. serratus Philip, 1963; Pliocene, Australia.
Classification and/or Status

Cidaroida, Cidaridae, Cidarinae.



Distinguished from the very similar Eucidaris by is more fusiform and more densely granulated spines, and by having clearly conjugate pore-pairs. Although Eucidaris does have subconjugate pore-pairs and specialized respiratory tube-feet they are never as pronounced as those in Phyllacanthus.

For an account of the fossil record of spines attributed to this taxon see Philip (1963).

Brandt, J. F. 1835 (May). Prodr. Descr. Anim. Rec. actes Acad. Imp. Sci. Petersburg [1834], p. 267.

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

Philip, G. M. 1963. The Tertiary echinoids of South-East Australia. Proceedings of the Royal Society of Victoria 76, 181-236, pls 21-26.