The Echinoid Directory

• Test rather angular with shallow but distinct anterior sulcus; posterior face truncate.
• Apical disc ethmophract with four gonopores (genital plate 2 separates posterior genital plates but not the posterior ocular plates); central.
• Ambulacrum III wide and sunken from apex to peristome. Pore-pairs circumflexed and differentiated from those of the petals.
• Paired ambulacra large and petaloid; petals modestly sunken and weakly bowed; extending almost to the ambitus; anterior and posterior petals subequal in length. Interporal zone wide; pore-pairs elongate and slit-like.
• Peristome small, pentagonal and downward facing.
• Plastron structure not reported in type species; large and triangular in P. calvini, extending to third ambulacral plate. Sternal plates unequal and median suture oblique. Episternal plates biserially offset.
• Periproct ovate, situated towards top of posterior truncate face.
• Incomplete peripetalous fasciole, developed around only the posterior half of the test.
• Aboral tuberculation of scattered small tubercles set in a groundmass of granules.

Lower Cenomanian (Aptian-Albian), North America, North Africa, Spain.

Palhemiaster peroni Lambert, 1916, p. 90, by original designation.

• P. peroni Lambert, 1916; Aptian-Albian, Algeria.
• P. ibericus Jeannet, 1936; Aptian, Balearic Islands.
• P. scotti Lambert 1932; Albian, Texas, USA [?=P. calvini Clark, 1915].
• P. calvini (Clark, 1893); Albian, Texas, USA.
• P. natalyae Jagt, Jagt-Yazykova & Zonova, 2013; Lower Campanian, Sakhalin.

Spatangoida, Hemiasterina, Hemiasteridae.

Presumably paraphyletic (by exclusion of Hemiaster, Mecaster and Jordaniaster).

Lambert erected this taxon for a species that resembled Hemiaster in appearance, but which had only a partial peripetalous fasciole. This taxon closely resembles Jordaniaster , but in that genus the peripetalous fasciole is more or less complete. Pliotoxaster differs in entirely lacking a fasciole.

Lambert, J. 1916. Sur l'existence de l'etage Valanginien et sur l'oscillation barremienne dans l'Aube et dans l'Yonne. Memoires  de la Societe academique de l'Aube 80, p. 19-94.

Lambert, J. 1920. Sur quelques genres nouveaux d\'Echinides. Memoires de la Societe Academique de l'Aube Series 3, 56.

Jeannet, A. 1935. Sur deux Echinides irreguliers du Cretace inferieur d\'Ibeza (Baleares). Proceedings of the Royal Academy of Amsterdam 38, 181-185.

Jagt, J. W. M., Jagt-Yazykova, E. A. & Zonova, T. D. 2013. Notes on selected Cretaceous echinoids from south-central Sakhalin, Far East Russia. Netherlands Journal of Geosciences / Geologie en Mijnbouw 92/2-3, 123-132.