Bathyporania ascendens Mah & Foltz, 2014, n. sp.

Bathyporania ascendens n. sp.

Figure 2 A–E

Etymology. Species epithet ascendens (=Latin for “ascending”) refers to the in situ observation of the animal’s climb up the upper branches of a deep-sea coral, where it was collected (Fig. 2 E).

Taxonomic comparison. The phylogenetic tree shown in Fig. 1, illustrates Bathyporania as sister taxon to “ Porania ” antarctica but the single individual sampled does not clarify monophyly of Bathyporania relative to “ Porania ” antarctica. Distinction of this taxon as a separate genus is based on several characters including the more densely arranged reticulate skeleton with more lobate abactinal plates, the polylobate marginal plates arranged horizontally (versus vertically in “ P.” antarctica), the absence of an actinolateral fringe of plates, the differnce in furrow spine morphology, actinal plate arrangements and differences in disk: arm ratio, including the outline of the arms. Adult size in the holotype of Bathyporania ascendens is also much smaller than those in “ Porania ” antarctica.

Shared characters between the two genera include furrow spines which are arranged transversely, a disparately sized larger superomarginal and a smaller (<50%) sized inferomarginal plate series, as well as flattened marginal plates. The presence of a reticulate skeleton suggests affinities with Clavaporania nov. gen., which otherwise appears different from Bathyporania.

Figure 1 places Bathyporania as the sister taxon to “ Porania ” antarctica (see change below). Bathyporania displays superficial resemblance with two species, Poraniomorpha abyssicola and P. tumida, which we have placed within the genus Rhegaster below. Bathyporania differs in several respects from both Poraniomorpha abyssicola and P. t u m i d a, including the presence of a broadly reticulate abactinal skeleton, spinelet-tipped abactinal and marginal plates and marginal plates with a differing lobate shape than that of Rhegaster. Character similarities are interpreted as plesiomorphies, including single papular pores, imbricate marginal plate arrangement, actinal plate arrangement, and actinal grooves aligned with inferomarginal plate contacts.

Occurrence. North Pacific, Davidson Seamount. 2669 m.

Although this represents first occurrence, it may share the widespread distribution that is observed in several abyssal asteroid taxa. However, given its small size there may be a bias against collection of this species by nets or submersibles.

Description. Body strongly stellate with arms slender (R/r=3.1), disk tumescent. Skeleton covered by overlying skin (underlying plates better seen in dry specimens) (Fig. 2 A, C, D). Surface smooth, but textured by underlying skeleton.

Abactinal surface composed of multilobate to irregularly round plates either abutted against one another more proximally or forming an open reticulate network more distally (Fig. 2 C, D). Each plate covered by one to four widely spaced, pointed spines with tiny spinelets (<0.4 mm tall) (Fig. 2 C, D) also present on plate periphery or on contact/boundaries between plates. Plates with more than one spine larger, more lobate, more irregularly shaped. Intervening surface smooth, devoid of accessories. Madreporite round but imperfectly circular (Fig. 2 A), set on a raised portion of disk. Madreporite periphery surrounded by ~12 spines, each on raised bases. Papulae present single to clusters of three or four between abactinal plates but absent below marginal plate series.

Superomarginals, approximately 34–36 per interadius, larger and multilobate proximally becoming smaller and oval/irregularly quadrate in outline distally (Fig. 2 D). Superomarginals arranged irregularly in series becoming more erratic distally. Superomarginals with one or two short, pointed spines, some with an additional two to four tiny spinelets present offset on plate surface. Inferomarginal plates, approximately 34–36 per interradius, smaller (50% of superomarginal size), more elongate and oval in shape. Disparity in size and shape more pronounced proximally with superomarginals and inferomarginals approaching similar size and shape distally. Inferomarginals with zero to five short spines, usually three or four, when present in a row or an irregular cluster.

Actinolateral surface flattened with distinct actinolateral boundary (Fig. 2 B). Actinal plates limited to disk, absent from arms. Actinal plates, each with a large spine present. Boundaries covered by skin. Skin folds form shallow grooves from inferomarginals to oral plate.

Furrow spines, three to four, pointed and covered by skin sheath-similar to skin covering over the body surface in transverse series. Shortest spine present deep in tube foot furrow. Furrow spines aligned with spines present in regular rows that align with inferomarginal plates/spines (Fig. 2 B). Other than spines, no other accessory structures (granules, etc.), body surface covered by smooth skin. Mouth plates surface bare, six furrow spines. Pedicellariae not observed.

Specimen examined. HOLOTYPE USNM 1215321. Davidson Seamount, 35° 37' 56 N, 122° 49' 35.2 W, (35.63239, -122.826457), 2669 m, Coll. James Barry, MBARI, st. T947-A15 (1 wet spec. R=2.2 r=0.7).