Seriaster Jangoux, 1984

Mah, Christopher L. & Fujita, Toshihiko, 2020, New species and occurrence records of Japanese Solasteridae and Ganeriidae including a new species of Paralophaster from the North Pacific with an overview of Hyalinothrix, Zootaxa 4750 (1), pp. 67-100 : 93

Seriaster Jangoux, 1984

Figure 10 A–D

Seriaster Jangoux, 1984 : 281,284; A. M. Clark 1996: 191

Comments. Seriaster was originally described in Jangoux (1984) and tentatively assigned to the Solasteridae based on the shape of the actinal plates as compared with Rhipidaster and abactinal plates from other solasterids including Solaster regularis and Lophaster . Jangoux (1984) also pointed out affinities between Seriaster and Chaetaster .

Examination of the adambulacral plates in both Seriaster and members of the Solasteridae revealed that they are distinctly different. Solasterids, using Rhipidaster as the exemplar ( Fig. 3 ), possess a wide adambulacral plate, each separated from the other plates by a distinct tissue filled space.

Seriaster , in contrast, lacks the large, wide transversely arranged adambulacral plate with the broad round facet and tissue-filled space between plates and has instead smaller more block-shape adambulacral plates present in a transverse series with each adambulacral plate facing separated by a small tissue-filled space ( Fig. 10D ). The adambulacral plates are abutted directly onto the adjacent inferomarginal, which in turn was in contact with the the parallel superomarginal plate. Both marginal plate series followed Blake’s (1978) definition for marginal plates in which the series tracks from the interradius to the arm terminus.

Seriaster also possesses abactinal plates in ordered imbricate series forming regular papular pores sitting between paxillae-like plates, exhibit hyaline spinelets on the abactinals and lacks the abactinal skeleton structure observed in solasterids, including the reticular, irregular skeleton observed in Rhipidaster or the paxillae-like plates sitting on round, imbricate plates observed in Lophaster .

Our skeletal observations disagree with the placement of Seriaster within the Solasteridae made by Jangoux (1984) and are more consistent with placement within the Hyalinothricinae.

Figures

FIGURE 3. Paralophaster gomo n. sp. Holotype, NSMT-E-11294. Scale bar=0.5 cm for all except B and C. A. Abactinal surface. B. Closeup of abactinal surface. Scale bar=2.0 mm. C. Oral surface. Scale bar=0.5 cm. D. Closeup of oral region. E. Small specimen showing large primary plates NMST E-11260.

FIGURE 10. Seriaster regularis. NSMT-E-10637. A. Abactinal surface. Scale bar=0.5 cm. B. Close-up of abactinal paxillae. Scale bar=1.0 mm. C. Oral surface. Scale bar=0.5 cm. D. Close-up of tube foot furrow and adambulacral plates. Scale bar=1.0 mm.