Kampylasterinae Mah 2023

The Kampylasterinae: A new subfamily within the Asterinidae

Kampylaster and Anseropoda were previously grouped together (see Spencer & Wright 1966) along with Mirastrella Fisher, 1940 within the Anseropodinae Fisher, 1906.Although a decisive placement was uncertain, A.M. Clark (1983) placed Mirastrella Fisher, 1940 with Leilaster A.H. Clark, 1938 in the Leilasteridae Jangoux & Aziz, 1988, separate from the Asterinidae. As discussed herein “ Anseropoda ” antarctica is separated from typological Anseropoda and thus, typological priority for the subfamily falls to the senior name, Kampylaster Koehler, 1920.

Based on both 2-gene and 3-gene trees, Kampylaster Koehler, 1920 and “ Anseropoda ” (now Astrotholus n. gen.) antarctica were supported as constituting a monophyletic clade within a larger Asterinidae + Ganeriidae cluster (Mah & Foltz 2011b). Although the Kampylaster + “ Anseropoda ” clade was well supported (100% bootstrap) its precise relationship to other taxa was more ambiguous and was supported as the sister taxon to different groups within the larger cluster. Complimentary to the molecular data, morphological characters shared between the two genera are readily identified, supporting a consistent subgrouping, the Kampylasterinae nov. subfam. within the Asterinidae. This subfamily is added to the three currently established groups within the Asterinidae, the Asterininae, Ganeriinae and Hyalinothricinae as defined by Mah & Fujita (2020).

Astrotholus and Kampylaster are similar in many respects, both lack superambulacral, transactinal, and superactinal plates, which are individually or partially present within most members of the Asterinidae (definition of terms follow O’Loughlin & Waters 2004).

Genera such as Stegnaster Sladen, 1889 have been argued as showing affinities with members of the Kampylasterinae. However, there has been contention concerning placement. Fisher (1911) placed Stegnaster within the Anseropodinae, which apparently met with disagreement by Spencer & Wright (1966) who placed Stegnaster closer to Tremaster in the “ Tremasterinae.” Although Stegnaster is not supported in the molecular phylogeny (Mah & Foltz 2011b) as an adjacent sister taxon to Kampylaster and “ Anseropoda ” antarctica it was supported as a member of a wider clade containing these taxa based on the 2-gene tree but was not included in their 3-gene tree. Close affinity of Stegnaster with the “ Kampylasterinae ” is plausible, although further work remains. Tremaster has historically also been shown to display morphological affinities, but is morphologically distinguished from Kampylaster and Astrotholus n. gen. based on the strongly developed imbricate surface plates, four series of tube feet, the presence of unusual internal chambers, and furrow spines in transverse series. The two-gene tree by Mah & Foltz (2011b) also showed Tremaster as being phylogenetically distant from the “ Kampylaster clade.”

Actinal intermediate plate patterns in Astrotholus n. gen. show similarity with the deep-water Paranepanthia platydisca (Fisher, 1913), the type species for Paranepanthia Fisher, 1917. in that two species of Astrotholus n. gen. both show transverse linear series which extend directly from the inferomarginal to the adambulacral plates. There is significant morphological disparity among Paranepanthia spp. and it is unclear if the deep-water species such as the typological P. platydisca forms a monophyletic group with shallow water forms such as Paranepanthia aucklandensis (Koehler, 1920).

Two-gene trees (Mah & Foltz 2011b, fig. 2) have shown the clade containing the Ganeriinae as sister to the Kampylasterinae. Cycethra, Perknaster and Cuenotaster, as members of the Ganeriinae show fenestrate (Cycethra and Cuenotaster) or greatly reduced skeletons (Perknaster) and demonstrate very different marginal and actinal plate patterns as well as body shape than what is observed in either Kampylaster or Astrotholus n. gen. Members of the Hyalothricinae all share fenestrate skeletons bearing paxillar or glassine spinelets which are absent in Kampylaster and Astrotholus. Mah & Fujita (2020) and Mah & Foltz (2011b) returned the Ganeriinae to the Asterinidae (following Sladen 1889) and moved the Hyalothricinae to the Asterinidae.

Key to genera of the Kampylasterinae

Granules only- with round surface, spinelets never present, forming continuous cover, obscuring plate boundaries. Furrow spines in transverse to oblique orientation relative to tube foot furrow. Actinolateral edge, thick to rounded............................................................................................... Kampylaster Fisher, 1940

Granules or spinelets, forming clusters conforming to underlying plates which range from flat to distinctly mound-like. Furrow spines parallel with tube foot furrow. Actinolateral edge angular................................. Astrotholus nov. gen.