OREASTERIDAE, Fisher, 1908

Mah, Christopher & Foltz, David, 2011, Molecular phylogeny of the Valvatacea (Asteroidea: Echinodermata), Zoological Journal of the Linnean Society 161 (4), pp. 769-788 : 778

THE OREASTERIDAE , ACANTHASTERIDAE, AND ASTEROPSEIDAE

Although still supported as a member of the Valvatida and/or Valvatacea in Figure 1 , the oreasterid/ asteropseid lineage has historically been considered as most closely related to either the Goniasteridae and/or the Ophidiasteridae . The close relationship between the oreasterids and asteropseids (node O in Fig. 1 ) agrees with Blake (1987) and Gale (1987b), but our topology agrees more closely with the tree of Blake (1987) in that it supports poraniids as a lineage separate from asteropseids. Gale (1987b) considered asteropseids as members of the same lineage as poraniids.

The Asteropseidae was not supported as monophyletic, supporting Asteropsis , Dermasterias , and Petricia on different lineages. Asteropsis most closely resembles the tree topology presented by Blake (1987) in that it is supported as sister taxon to the goniasterid-like oreasterid Monachaster on the sister clade to the large primary Oreasteridae ( Culcita , Oreaster , etc.). Petricia was supported as the sister taxon to Acanthaster . Dermasterias was supported as the sister taxon to the Asterinidae + Solasteridae + Ganeriidae + Leilasteridae in the three-gene tree (node P in Fig. 1 ) with moderate bootstrap support (65%). Although we used the relationships in Figure 1 as the basis of rooting the asterinid tree in Figure 2 , placing the root at the branch subtending node 2 rather than at node 1 would still leave the asterinid tree monophyletic and would group Dermasterias with the remaining members of the asteropseid/ oreasterid clade, which is more consistent with prior classifications (e.g. Hotchkiss & Clark, 1976).

Acanthaster is supported as the sister group to the included oreasterids, which is consistent with the close relationship between the Acanthasteridae and the Oreasteridae as supported by Blake (1979, 1987) based on skeletal evidence. In our tree, the ( Oreasteridae + Asteropseidae ) + Acanthasteridae / Asteropseidae clade is supported (node N in Fig. 1 ) as the sister clade to the large Asterinidae + Ganeriidae + Leilasteridae + Solasteridae + Dermasterias clade, which is a substantial departure from prior phylogenetic hypotheses.

The presence of Acanthaster as the sister taxon to the Oreasteridae + Asteropsis is consistent with the morphological evidence and phylogenetic hypothesis of Blake (1979, 1987). He documented an Eocene oreasterid ( Blake, 1979) that was close to Anthenea or Goniodiscaster and showed a morphology demonstrating characters consistent with Acanthaster and other Oreasteridae . Thus, oreasterid fossil occurrence can be shown to be present in the Eocene. Otherwise, there are relatively few oreasterid fossils known and most are either too poorly known or too incomplete to be useful here.

Figures

Figure 1. Maximum likelihood tree of valvatacean sea stars rooted against forcipulatacean + velatid sea stars. The analysis is based on 1084 bp of concatenated sequence data from two mitochondrial rDNA genes and one nuclear protein-coding gene, early-stage histone H3. As discussed in the text, solasterids are treated as part of the ingroup. The analysis was carried out in RAxML with bootstrap percentages indicated for nodes that had> 50% support. Boxed letters A–P are referred to in the text. Traditional family names are shown at the right; all families are in the Valvatida except as noted. The scale bar shows the expected number of substitutions.

Figure 2. Maximum likelihood tree of asterinid + solasterid sea stars rooted against closely related valvatid sea stars. The analysis is based on 1417 bp of concatenated sequence data from two mitochondrial rDNA genes. Circled numbers 1 and 2 are referred to in the text. Other details as in Figure 1.