Systematics, phylogeny and historical biogeography of the <i>Pentagonaster</i> clade (Asteroidea: Valvatida: Goniasteridae
Morphology-based phylogenetic hypotheses developed for living and fossil goniasterid asteroids, have provided several unique opportunities to study bathymetric and biogeographic shifts for an ecologically important group of prominent, megafaunal invertebrates. A cladistic analysis of 18 ingroup taxa employing 65 morphological characters resulted in a single most parsimonious tree. The tree supports assignment of the Atlantic Tosia parva and the Pacific Tosia queenslandensis to new, separate genera. The phylogenetic tree supports offshore-onshore bathymetric shifts between basal and derived taxa. The phylogeny is also consistent with historical events surrounding the separation of Antarctica from Australia and South Africa. Buterminaster from the Eocene La Meseta Formation, Antarctic Peninsula, was included in the phylogenetic analysis and is now supported as the only fossil species in the genus Pentagonaster. Pentagonaster stibarus is separated from synonymy of P. dubeni and resurrected as a species. The new genus Akelbaster shows unusual new structures that resemble cribiform organs, although their function has not been determined. One specific ingroup lineage, including Tosia and Pentagonaster attains a much larger adult size than those of a sister group and including basal taxa, suggesting that Cope’s Rule may apply to asteroids within this clade. Pentagonaster and related genera are revised; descriptions of four new genera and three new species are presented, including Akelbaster novaecaledoniae gen. nov., sp. nov., Ryukuaster onnae gen. nov., sp. nov., Eknomiaster beccae sp. nov., Pawsonaster parvus gen. nov., comb. nov., and Anchitosia queenslandensis gen. nov. comb. nov.
Australia to South-east Asia