Xyloplax is a genus of three species of sea stars previously found only on sunken wood in the deep ocean. Their circular and petaloid bodies, which lend them their common name “sea daisy”, and their presumed exclusive diet of wood make them an unusual and rare element of deep-sea ecosystems. We describe here the fourth species of
Xyloplax from the eastern Pacific Ocean,
Xyloplax princealberti n. sp., which ranges from offshore Canada to the Gulf of California (Mexico) and Costa Rica. Though sampled geographically close to another described species of
Xyloplax from the northeastern Pacific,
X. janetae, this new species is unique morphologically and according to available DNA data. The short abactinal spines are the most obvious feature that distinguishes
X. princealberti n. sp. from other
Xyloplax. The minimum distance for mitochondrial cytochrome c oxidase subunit I from
Xyloplax princealberti n. sp. to the only other available
Xyloplax,
X. janetae, was 13.5%. We also describe
Ridgeia vestimentiferan tubeworm bushes from active hydrothermal vents as a new
Xyloplax habitat, the first record of a non-wood substrate, and a new reproductive strategy, simultaneous hermaphroditism, for this genus. We generated the first mitochondrial genome for a member of
Xyloplax and analyzed it with other available asteroid data using nucleotide-coding or amino acid (for protein-coding genes) plus nucleotide coding (for
rRNA genes). The nucleotide-coding results place
Xylopax as part of the clade Velatida, consistent with a previous phylogenomic analysis that included
Xyloplax princealberti n. sp. (as
Xyloplax sp.), though the placement of Velatida within Asteroidea differed. The amino acid plus nucleotide coding recovered Velatida to be a grade with
X. princealberti n. sp. as sister group to all other Asteroidea.
Full article