Schizaster

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

Belongs within: Hemiasterina.

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. africanus G92
    |         ‘Spatangus’ ambulacrum Deshayes 1831 [=*Brachybrissus ambulacrum] F66
    |         S. eurynotus Agassiz 1836 [=*Aplospatangus eurynotus] F66
    |         S. fragilis D66
    |--*S. (Schizaster) studeri Agassiz 1836 F66
    |--S. (Hypselaster Clark 1917) F66
    |    `--S. (*H.) limicola Agassiz 1878 [=S. (Periaster) limicola] F66
    |--S. (Ova Gray 1825) F66 [=Ovum de Blainville 1830 A66; incl. Nina Gray 1855 F66]
    |    `--S. (*O.) canaliferus (Lamarck 1816) [=Spatangus canaliferus] F66
    |--S. (Paraster Pomel 1869) [incl. Prymnaster Koehler 1914, Rotundaster Lambert & Thiéry 1925] F66
    |    |--S. (*P.) gibberulus Agassiz 1847 F66
    |    |--‘*Prymnaster’ angulatus Koehler 1914 F66
    |    `--S. (P.) foveatus Agassiz 1889 [=*Rotundaster foveatus] F66
    `--S. (Tripylaster Mortensen 1907) F66
         `--S. (*T.) philippii (Gray 1851) [=Tripylus philippii] F66

*Type species of generic name indicated

REFERENCES

[A66] Anon. 1966. Doubtful nominal genera of echinoids. In: Moore, R. C. (ed.) Treatise on invertebrate Paleontology pt U. Echinodermata 3 vol. 2 pp. U633. The Geological Society of America, Inc., and The University of Kansas Press.

[D66] Durham, J. W. 1966. Echinoids—ecology and paleoecology. In: Moore, R. C. (ed.) Treatise on invertebrate Paleontology pt U. Echinodermata 3 vol. 2 pp. U257–U265. The Geological Society of America, Inc., and The University of Kansas Press.

[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.