Squamophis lifouensis, Stöhr, Sabine, 2011

Stöhr, Sabine, 2011, New records and new species of Ophiuroidea (Echinodermata) from Lifou, Loyalty Islands, New Caledonia, Zootaxa 3089, pp. 1-50 : 10-12

Squamophis lifouensis sp. nov.

Figures 2–3

Type material. Holotype, in 80% ethanol, sta. 1469, off Cap Lefévre, bank, 20°54.2' S, 167°00.4' E, 70–130 m [ MNHN IE- 2009-9200]; skeletal elements on SEM stubs [ MNHN IE- 2009-9201]. Paratype from type locality, in 80% ethanol, [SMNH-Type-8076].

Etymology. The specific name alludes to the type locality.

Holotype description. Disk diameter 4.8 mm, five non-branching arms, strongly coiled. One arm broken off at disk (but preserved), one arm narrower and probably regenerating. Disk surface folded, centre sunken in. Dorsal disk and arms covered with large, flat, smooth, round to oval granules, embedded in thick skin, completely obscuring any scales or plates. Arms inflated proximally, although constricted at disk, elsewhere as wide as high, ventral side flat, tapering distalwards. Radial shield (exposed after bleaching) composed of single ossicle, with a long barlike branch extending for about two thirds of the disk radius and a wider, short branch distally. Inflated part of arms supported by rib-like processes at lateral arm plates, forming a gonadal chamber.

Arms covered dorsally and laterally with similar granules as the disk, embedded in thick skin; double bands of granules, interspersed with bands of skin with small scales or granules. At the latero-ventral edge of the arms a dense covering of small round granules. A single thick, blunt, slightly club-shaped arm spine as long as an arm segment, along most of the arm, at the distal arm transformed into a hook with three teeth.

Ventral disk, oral frame and arms with thick skin and tiny flat, round granules (dermal ossicles) obscuring any plates. Ventral interradii vertical, bursal slits at arm bases as long as disk. Each jaw bears five pointed triangular teeth, larger low, round granules at tip of jaws and lateral edges, also higher up at jaw sides. Adoral shields large, rounded triangular. Oral shield minute at vertical edge. Second tube foot outside of mouth angle, no tentacle scales. Gonads extend into arms.

Vertebrae with streptospondylous articulation and open ventral furrow. Dorsal and ventral arm plates lacking. Lateral arm plates curved around the vertebrae, bearing a massive spine articulation, consisting of two upwards curved strong ribs, connected at their dorsal end, open ventralwards, with a deep wide furrow between them. There is a hole between the ribs (presumably the muscle opening) and another in front of them (presumably the nerve opening).

Colouration creamy white with narrow reddish brown bands on the disk, forming a reticulating pattern. On arms horizontal white bands largely correlated with the large granules, and narrow brown bands. Ventral side uniformly white.

Paratype variations. Disk diameter 3 mm, arms not swollen, disk without folds, otherwise similar to the holotype. This is clearly a juvenile specimen with immature gonads. It is attached to a piece of black coral, Antipathes sp.

Remarks. The open vertebrae of streptospondylous type and the absence of hook girdles on the arms place this species in the family Asteroschematidae . Among the asteroschematid genera, Ophiocreas has a thick, smooth, naked skin, while Astrocharis has small naked radial shields and very small arm spines (Okanishi & Fujita 2011). Mortensen (Mortensen & Stephensen 1918) concluded that the presence of inflated arm bases, previously used to differentiate Astrocharis from Asteroschema is not useful as a generic character, since Astrocharis gracilis Mortensen, 1933 lacked swollen arms. Okanishi et al. (2011b) also found that this character is not reliable. In addition, the arms may be swollen in some Ophiocreas species (personal observation), whereas they are not swollen in juveniles (see the paratype of the new species). Okanishi et al. (2011b) recognized morphological and molecular ( Okanishi et al. 2011a) differences between the species until then included in Asteroschema and proposed a new FIGURE 2. Squamophis lifouensis sp. nov., A–C, holotype MNHN IE-2009-9200, D, E, paratype SMNH-Type-8076; A, dorsal aspect; B, ventral aspect; C, exposed radial shield; D, dorsal aspect; E, arm details, note the club-shaped single spines. Scale bars 1 mm.

FIGURE 3. SEM images of skeletal elements of Squamophis lifouensis sp. nov. holotype MNHN IE-2009-9201. A, proximal vertebra distal face, streptospondylous articulation; B, proximal vertebra proximal face; proximal vertebra lateral aspect; D, lateral arm plate external, note the large spine articulation; E, lateral arm plate internal. Scale bars 0.1 mm.

genus, Squamophis , for those species that have flat dermal ossicles completely covering the disk and radial shields, single ossicle radial shields, and arm spines as long as an arm segment. The new species shares all of these characters and thus is best placed in Squamophis . A tissue sample of the holotype was sequenced for several genes by Okanishi and the data also placed the new species within Squamophis (Okanishi, personal communication). Also, the colour pattern is unusually conspicuous for Asteroschema , but not for Squamophis . Its closest affinities are with A. igloo Baker, 1980 , a species suggested by Okanishi et al. (2011b) to belong in Squamophis , from which it differs in larger and flatter granules and the presence of only a single arm spine (two in A. igloo ), and S. amamiensis ( Okanishi & Fujita 2009) , from which it differs in smooth arm spines, slightly larger, not as densely placed dermal ossicles, and in colour pattern. Squamophis lifouensis sp. nov. differs from S. albozosteres Okanishi et al., 2011 in larger dermal ossicles, in the shape of the radial shield and in colour pattern. The massive spine articulation of the new species differs from the shape indicated for Gorgonocephalidae and Asteronychidae by Martynov (2010a) and from the large half-circle shaped opening with protruding lower lip found in Asteroschema tubiferum Matsumoto, 1915 and Ophiocreas sibogae Koehler, 1904 (unpublished personal observations), but does not concur with any shape found in Ophiurida either. This may be additional support for the genus Squamophis .

Distribution. Known only from the type locality.