Ophiohamus georgemartini, O’Hara, 2015

O’Hara, Timothy D., 2015, Enigmatic ophiuroids from the New Caledonian region, Memoirs of Museum Victoria 73, pp. 47-57 : 47-49

Ophiohamus georgemartini sp nov

Fig. 1

Zoobank LSID. http://zoobank.org/ urn:lsid:zoobank.org:act:

11DC6E76-463D-42BE-AD04-25622254FB64

Type material. – New Caledonia. SMIB5 : stn DW94, Banc Alis , 22° 19.6'S, 168° 42.8'E, 275 m, 10 Sept 1989, holotype : 1 (MNHN IE.2013.16001).

Description. Disc 3.8 mm diameter, arms (all broken at tip) at least 10 times d.d., curved but not coiled. Disc circular, without interradial incisions, dominated by 5 pairs of large triangular radial shields, with rounded angles, 0.35 times d.d., contiguous for most of their length radially, separated at the distal and proximal ends by small scales, the former a small triangular plate, possibly homologous to the dorsal arm plates. One row of 3-4 polygonal interradial plates separate the radial shields and a cluster of irregular rounded overlapping disc scales centrally. A large conical spine is present on the distalmost plate of each interradius, 0.7 mm high and 0.5 mm in diameter at the base. On one interradius, there is a second conical spine on the next proximal interradial plate, on another interradius there are two small round granules, 0.14 mm diameter; 1-2 similar granules are also present on some central plates.

Ventral disc covered in several rows of polygonal or rounded overlapping scales. Wide genital slits. Oral shields diamond shaped, two times as wide as long. Adoral shields thick, sausage-shaped, proximal to oral shields, contiguous interradially, twice as wide as long, extending beyond the lateral angles of the oral shields, beaded surface. Apical papilla conical, twice as high as wide; three slender subequal oral papillae borne on the oral shields, the distal papilla abutting the adoral shield and overlying the second oral tentacle pore.

Dorsal arm plates rounded triangular, with straight lateral edges and slightly convex distal edge, first two plates just contiguous, others separated widely by the lateral arm plates. First ventral arm plate small, projecting into jaw space, contiguous with the second plate. Succeeding ventral arm plates pentagonal at first, but from segment three becoming more rectangular or rounded, separate, without a proximal angle, longer than wide, lateral sides incurved to accommodate the pore, distal edge convex to truncate. Lateral arm plates with striated surface for much of the arm, with a large distal flange bearing up to four arm spines. Separated ventrally by a small uncalcified area basally. Basal arm spines conical with a blunt tip, three times as high as the basal diameter, 1.3 segments long, middle spines flattened and covered in minute thorns, restricted to the lateral side of the arm after the first two segments. Four arm spines persist to (near) arm tip, becoming slender and pointed, uppermost spine exceeding a segment in length, lowest half that length, becoming hooked (curved and rugose on the proximal side). Arm spine articulation, rounded volute-shape. A single oval tentacle scale covers the small tentacle pore, as long as one third of the ventral arm plate.

Colour (dry): white. Arms originally curved around a small hollow glass sponge.

Distribution. New Caledonia (275 m)

Remarks. The volute-shaped arm spine articulation surface and overall appearance indicates that this species is an Ophiacanthidae ( Martynov 2010) . Within this family, the new species is closest to the genera Ophiomitrella and Ophiohamus , having relatively large disc scales and radial shields, the former often bearing spines/granules, but lacking the deep interradial disc incisions characteristic of Ophioplinthaca or the enlarged ventral interradial disc scale characteristic of Ophiurothamnus . The new species bears a strong resemblance to Ophiohamus nanus O’Hara & Stöhr, 2006 in the shape of the disc plates, radial shields, arm plates and arm spines, adoral and oral shields. But O. nanus differs in having no disc spines or granules; relatively small radial shields, 1/4 d.d.; several rows of disc scales interradially; only two oral papillae on most jaw sides, the outer being widened; and only three arm spines distally. The new species lacks the interradial incision present on the holotype of O. nanus but this was not consistently present on the paratypes. Some species of Ophiomitrella and Ophiurothamnus have large disc spines or tubercles, either cylindrical ( Ophiomitrella nugator ( Koehler, 1922a) , Ophiurothamnus excavatus Koehler, 1922a ) or capitate ( Ophiomitrella conferta ( Koehler, 1922b)) but they are never as robust and conical as the marginal spines in the new species.

The genus-level classification of the Ophiacanthidae is inadequate ( O’Hara & Stöhr 2006), with the large genera Ophiacantha and Ophiomitrella being polyphyletic (O’Hara & Hugall unpublished genetic data). Until a new classification is proposed, we place the new species in Ophiohamus . However, this requires an amendment of the generic diagnosis to accommodate a species with no interradial disc incision, as follows: Disc covered with coarse overlapping disc plates and large contiguous radial shields that are integrated into the disc plating, spines may be present, a shallow interradial incision in disc margin may be present, 2-3 spiniform oral papillae, with a widened outer papillae replacing the distal two, small oral and adoral shields, oral shields contiguous with the lateral arm plate and lying distal to the adoral shields, oral tentacles enclosed within jaw slit. Arms can curve ventrally but don’t coil, small mostly separate dorsal and ventral arm plates, 3-4 arm spines restricted to the lateral side of the arm, relatively short, up to, or just exceeding, a segment in length, lowest spine semi-hooked, small tentacle pore covered by a simple tentacle scale.

Etymology. Named after the author, George R.R. Martin, because the large marginal disc spines of the new species look similar to the crown on the cover of his second book in the ‘Games of Thrones’ series, ‘A Clash of Kings’.