Dipsacaster antillensis Halpern 1968

Dipsacaster antillensis Halpern, 1968:231–240

Among the seastars collected by the Alaminos in the middle of the Gulf of Mexico were two small specimens of Dipsacaster antillensis, described from the western Atlantic by Halpern (1968), from Little Bahama Bank, in less than 900 meters. These two small specimens are from the middle of the Gulf of Mexico, in depth greater than 3,200 meters. They are evidently juveniles of D. antillensis, and quite apart from size (much smaller than Halpern’s specimens), have quite small dorsal paxillae, not at all compact at least on the arms; the paxillar spinules are longer, finer, and very thorny; the inferomarginals are armed with a central, rather than distomarginal, group of spines, at least one of which is quite thick and thorny; massive pedicellariae are present on some of the inferomarginals, the actinal interradials, and many of the adambulacral plates; the adambulacral furrow spines are fewer in number and distinctly palmate; the madreporite is, as yet, rather small and concealed by enlarged paxillae.

The disc is large, but the arms are moderately long, narrow, and tapered, rather than being broad and subpetaloid as in most Dipsacasters; in this and in the armature of the inferomarginals, they resemble D. nesiotes Fisher (1910b), but the dorsal paxillae are decidedly different from those of Fisher’s Hawaiian species. These specimens are quite obviously juvenile, but Dr. Halpern has examined these and other specimens and determined that they are indeed young D. antillensis.

MATERIAL EXAMINED.–Alaminos Stations: 9/69–A–13 (1) [R=12 mm, r=4 mm, Rr=1:3]; 29/69–A 13 (1) [R=12 mm, r=3.5 mm, Rr=1:4].

This family is mainly distinguished by having cribriform organs between all the marginals; they are continuous with channels on the oral surface covered with webbed spinelets, between transverse rows of plates. The marginals are thin, high, and lamelliform, smooth and covered with membrane. The two rows of tube feet are pointed and the ampullae are single. Superambulacral ossicles are present. The abactinal surface is paxillose.