A new Xyloplax species (Asteroidea, Echinodermata) that is not always associated with woodfalls

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, makes them an unusual and rare element of deep sea ecosystems. We describe a fourth species of Xyloplax from the eastern Pacific Ocean that 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 by available DNA data. Additionally, we describe Ridgeia vestimentiferan tubeworm bushes from active hydrothermal vents as a new habitat, the first record of a non-wood substrate, and a new reproductive strategy, simultaneous hermaphroditism, for this genus.