The Echinoid Directory

Asterostoma Agassiz, in Agassiz & Desor 1847, p. 168

Diagnostic Features	Test ovate without anterior sulcus at ambitus; base flat; upper surface domed. Apical disc anterior of centre with four gonopores; plating ethmolytic; madreporite plate extending far to rear of posterior oculars. Anterior ambulacrum narrow and flush aborally; pore-pairs simple. Paired ambulacra petaloid; flush; extending to ambitus; open distally, without occluded end plates. Peristome subcentral; pentagonal in outline, wider than long. Ambulacra on oral surface in shallow grooves with extensive phyllodes; phyllode pores single and extending more or less to ambitus. Plastron plating; labral plate moderately elongate, extending to ambulacral plate 2. Sternal plates long and triangular; extending to ambulacral plate 15+; episternal plates only weakly offset; not indented to rear by adjacent ambulacral plates. Periproct large, marginal to inframarginal; framed by interambulacral plates 5a5/5b5 on its oral side. No fascioles.
Distribution	Eocene, Caribbean.
Name gender	neuter
Type	Asterostoma excentricum Agassiz, in Agassiz & Desor, 1847, p. 168, by monotypy.
Species Included	A. excentricum Agassiz, 1847; Eocene, Jamaica, Cuba. A. pawsoni Kier, 1984; Eocene, Jamaica. A. subcircularis Sanchez Roig, 1952; Middle Eocene, Cuba.
Classification and/or Status	Spatangoida, Asterostomatidae. Presumed monophyletic.
Remarks	Differs from all other spatangoids in having a subcentral peristome and with large numbers of oral plates bearing phyllode tube-feet that extend almost to the ambitus in all five ambulacra. The ambulacra form grooves leading to the persitome on the oral surface. Kier (1984) argued that this taxon was so different that it deserved its own family. It differs from Stomaporus in having the periproct inframarginal rather than slightly supramarginal, in having no anterior sulcus, and in having somewhat more extensive phyllodes (if Cotteau\'s drawings are to be believed). Agassiz, L. & Desor, P. J. E. 1846-1847. Catalogue raisonné des familles, des genres, et des espèces de la classe des échinodermes. Annales des Sciences Naturelles, Troisième Série, Zoologie: 6 (1846), 305-374, pls 15-16; 7 (1847), 129-168; 8 (1847), 5-35, 355-380. Arnold B. W. & Clark, H. L. 1927. Harvard University Museum of Comparative Zoology Memoir 50, 62-63, pl. 15, fig. 3, pl. 16, pl. 17. Kier, P. M. 1984. The fossil spatangoid echinoids of Cuba. Smithsonian Contributions to Paleobiology 55, 1-334.