Lateral view (anterior to right) of Schizaster studeri, from the Natural History Museum.

Belongs within: Schizasteridae.

Schizaster is a genus of high-tested heart urchins known from the Eocene to the present (Fischer 1966).

Characters (from Fischer 1966): Test high, sloping anteriorly from posterior vertex, beaked over periproct; ambulacra sunken, frontal one deeply depressed; posterior petals 0.3 to 0.5 as long as anterior pair; apical system ethmolytic with two to four gonopores.

Schizaster Agassiz 1836 [incl. Aplospatangus Lambert 1907, Brachybrissus Pomel 1883]F66
| i. s.: S. africanusG92
| ‘Spatangus’ ambulacrum Deshayes 1831 [=*Brachybrissus ambulacrum]F66
| S. eurynotus Agassiz 1836 [=*Aplospatangus eurynotus]F66
| S. lyoniH79
| S. moseleyiD05
| S. rotundatusH79
|--*S. (Schizaster) studeri Agassiz 1836F66
`--S. (Paraster Pomel 1869) [incl. Prymnaster Koehler 1914, Rotundaster Lambert & Thiéry 1925]F66
|--S. (*P.) gibberulus Agassiz 1847F66
|--*Prymnaster’ angulatus Koehler 1914F66
|--‘Paraster’ doederleni Chesher 1972SS05
|--S. (P.) foveatus Agassiz 1889 [=*Rotundaster foveatus]F66
`--S. (P.) tatei McNamara & Philip 1980MM22

*Type species of generic name indicated


[D05] Döderlein, L. 1905. Arktische Seeigel. In: Römer, F., & F. Schaudinn (eds) Fauna Arctica. Eine Zusammenstellun der arktischen Tierformen, mit besonder Berücksichtigung des Spitzbergen-Gebietes auf Grund der Ergebnisse der Deutschen Expedition in das Nördliche Eismeer im Jahre 1898 vol. 4 pp. 373–394. Gustav Fischer: Jena.

[F66] Fischer, A. G. 1966. Spatangoids. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt U. Echinodermata 3 vol. 2 pp. U543–U628. The Geological Society of America, Inc., and The University of Kansas Press.

[G92] Gingerich, P. D. 1992. Marine mammals (Cetacea and Sirenia) from the Eocene of Gebel Mokattam and Fayum, Egypt: stratigraphy, age, and paleoenvironments. University of Michigan Papers on Paleontology 30: i–ix, 1–84.

[H79] Haast, J. von. 1879. Geology of the Provinces of Canterbury and Westland, New Zealand. A report comprising the results of official explorations. “Times” Office: Christchurch.

[MM22] McNamara, K. J., & S. Martin. 2022. Middle Eocene echinoids from the western Eucla Basin, Western Australia. Records of the Western Australian Museum 37: 31–56.

[SS05] Stockley, B., A. B. Smith, T. Littlewood, H. A. Lessios & J. A. Mackenzie-Dodds. 2005. Phylogenetic relationships of spatangoid sea urchins (Echinoidea): taxon sampling density and congruence between morphological and molecular estimates. Zoologica Scripta 34: 447–468.

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