Leilaster radians (Perrier 1881)

Leilaster radians (Perrier)

Korethraster radians Perrier, 1881a: 12.

Korethraster hispidus Perrier [non Wyville Thomson], 1884:212, pl 6: figs. 9–11.

Solaster radians–Perrier, 1884:275 [in explanation of plates], pl. 6: figs. 9–11.

Lophaster radians.–Perrier, 1884:167–170 [in list of species].

Korethraster ? radians.–Sladen, 1889:459, 463.

Leilaster radians.–A. H. Clark. 1938:1–7, pl. 1.

This small form has a broad disc and five moderately long, broad arms. The disc is strongly arched upward and the downward-directed arms, high in the midregion, slope off steeply at the sides. The tumid dorsal plates are oblong except at the disc center, where the primary plates are round. Papulae are single and confined to the radial areas. The plates on the arms are in regular longitudinal rows, a carinal and two adradials extending the full length of the arm; between the second adradial row and the superomarginals are one or two additional rows which do not reach the end of the arm. The second adradials are larger than the carinals and the first adradials. The plates imbricate upon one another in the direction of the disc. The large blocklike superomarginals are rectangular and vertical. The inferomarginal plates are paxilliform, with the plate produced in a stout column extending downward. All abactinal plates bear short clavate spinules with thick, rounded, thorny heads, so the general appearance of the dorsum is openly granular. The spinules of the dorsum are so spaced that conspicuous channels occur between the plates, and a broad sulcus is present in the interradius. The inferomarginals bear, on the outer edge, spinules of quite a different character: large, stout, and conical.

There is a single row of small actinal plates between the inferomarginals and the adambulacral plates, unornamented or bearing one or two small spinules. The adambulacral plates bear a furrow series of three long acute spines, webbed together and nearly parallel to the groove, the proximal spine shorter than the other two. On the actinal face of the plate is a comb of three longer spines in transverse series, incompletely webbed. The mouth plates are long and broad, and bear six long, subacute, divergent spines on the margin. In the specimens on hand, the actinal face of the mouth plate is bare. The madreporite is small, inconspicuous, and slightly sunken between two of the primary dorsal plates. The oculars are large and cordiform.

This odd little species is a classificatory puzzle; Clark placed it in the Ganeriidae, and Fisher (1911a) does not disagree, although he points out its affinities with the genera Mirastrella and Kampylaster, of the family Asterinidae. The character of the inferomarginal plates is quite like the genus Lophaster, of the family Solasteridae. The ill-defined Ganeriidae are a rather unsatisfactory family whose systematic position is open to question.

This species has previously been reported from Cuba, Barbados, and Puerto Rico, in 56–140 fathoms.

MATERIAL EXAMINED.—Oregon Station 4226 (6) [R=8 mm, r=4 mm, Rr=1:2].

It is interesting that this family, commonly represented in colder waters by medium to large species, should apparently be limited in the Caribbean and Gulf of Mexico to very small, immature-looking species. Verrill (1915) reported Poraniella regularis (R=12 mm), Poraniella echinulata (R=5 mm), Marginaster pectinatus (R=5 mm), and Porania ? austera (R=17 mm), and speculates that they may be juveniles of some species of Porania. I find this hard to believe, as at least some of the specimens were sexually mature, and no larger Poraniidae have been taken in this area. All of the above species were taken in 23–163 fathoms.

Systematically, this whole family is in need of revision, consisting as it does of very diverse forms, related variously to the Asterinidae, the Echinasteridae, the Ganeriidae, and the Oreasteridae, far removed in the currently accepted classification. Poraniella, as Verrill pointed out, is very close to Asterina, in the family Asterinidae; Spoladaster, according to Fisher, is close to Perknaster, in the family Ganeriidae; and Pseudoporania and Sphaeriaster seem close to some of the Oreasteridae (notably Culcita). Chondraster and Tylaster may lack any skeleton except for certain radial elements, and it is hard to see why they should be placed in this family rather than practically any other. As presently constituted, the family Poraniidae defies reasonable definition.

Poraniella Verrill

Poraniella Verrill, 1914:19. [Type, by original designation, P. regularis Verrill.]