The Echinoid Directory

Schizobrissus Pomel, 1869, p. 13

[ =Deakia Pavay, 1875, p. 152, type species D. rotundata Pavay, 1875; =Peripneustes Cotteau, 1875, p. 88, type species Peripneustes clevei Cotteau, 1875; =Rojasia Sanchez Roig, 1951, p. 58, type species R. rojasi Sanchez Roig, 1951]

Diagnostic Features
  • Test ovate with deep and well-defined anterior sulcus. Broad, flat base and low domed upper surface.
  • Apical disc ethmolytic, with 4 gonopores. Madreporic plate projecting well to the posterior of the other apical disc plates.
  • Anterior ambulacrum narrow with small, simple isopores; deepening towards ambitus.
  • Other ambulacra petaloid and sunken, the anterior pair almost at 180 degrees near apex but flexed anteriorly. Petals straight-sided; closed distally; occluded plates at petal ends.
  • Periproct large; on short undercut posterior face.
  • Peristome wider than long; kidney-shaped; close to anterior.
  • Labral plate short and wide, in broad contact with following sternal plates; not extending beyond first ambulacral plate.
  • Sternal plates large and followed by symmetric episternal plates which form the rear third of the plastron.
  • Primary tubercles differentiated inside peripetalous fasciole, especially prominent in anterior interambulacra. Areoles not sunken.
  • Well-developed peripetalous and subanal fascioles. Subanal fasciole bilobed. Peripetalous fasciole angular and deeply indented behind anterior petals.
Distribution
Eocene to Upper Miocene, Hungary, circum-Mediterranean, East Atlantic.
Name gender masculine
Type
Brissus cruciatus Agassiz, in Agassiz & Desor, 1847, p. 14 (120), by original designation. According to Lambert & Jeannet (1928, p. 198) the type referred to is T75 in the Neuchatel collection of moulds.
Species Included
  • S. cruciata (Agassiz, 1847); Lower to Upper Miocene, circum Mediterranean and Moroccan Atlantic coast.[?= S. locardi (Cotteau, 1877); = S. latus Wright, 1855]; Lower to Upper Miocene, western Mediterranean.
  • S. rotundata (Pavay, 1875); Eocene, Hungary.
  • S. antillarum Cotteau, 1875; Oligo-Miocene, Caribbean.
  • S. insignis (Duncan & Sladen, 1883); Middle Eocene, India, Pakistan
Classification and/or Status

Spatangoida, Micrasterina, Brissidae.

Presumed monophyletic.

Remarks

Chesher (1970) rejected this genus because he thought it was based on an indeterminate species. However, as Lachkhem & Roman (1995) point out, the type species is well known and the species clearly distinct from the type species of Meoma.

Philippe (1998) treated Schizobrissus as a subgenus of Meoma while Kroh (2005, p. 175) followed Chesher in treated it as unrecognizable (being based on a single, poorly preserved specimen that cannot be determined confidently even at family level).  However, according to Lambert & Jeannet (1928, p. 198) the type referred to by Agassiz is T75 in the Neuchatel collection of moulds, and is unambiguously assigned to Schizobrissus criciatus by those authors.

Kroh (2005) also pointed out that S. cruciatus (of later authors)  and S. locardi were simply larger and smaller individuals of the same species.

The principal difference separating Schizobrissus from Meoma is the depth of the frontal groove; deep in Schizobrissus almost from the apex, and shallow in Meoma, only weakly indenting the ambitus

Chesher, R. H. 1970. Evolution in the genus Meoma (Echinoidea: Spatangoida) and a description of a new species from Panama. Bulletin of Marine Science 20, 731-761.

Lachkhem, H. & Roman, J. 1995. Les echinoides irreguliers (Neognathostomes et spatangoides) du Messinien de Melilla (Maroc septenrional). Annales de Paleontologie 81, 247-278.

Lambert, J. & Jeannet, A. 1928. Nouveau catalogue des moules d\'Echinides fossiles du Musee d\'Histoire naturelle de Neuchatel. Memoires de la Societe Helvetique des Sciences Naturelles 64(2), 83-233, 2 pls.

Kroh, A. 2005. Catalogus Fossilium Austriae Band 2. Echinoidea neogenica. Verlag der Osterreichischen Akademie der Wissenschaften.

Philippe, M. 1998. Les echinides Miocenes du Bassin du Rhone: revision systematique. Nouvelles Archives Museum d\'Histoire Naturelle de Lyon  36, 1-439.

Pomel, A. 1869. Revue des echinodermes et leur classification pour servir d\'introduction a l\'etude des fossiles. lxvii pp, Paris.