Ophiodaphne impellera, O’Hara, 2015

O’Hara, Timothy D., 2015, Enigmatic ophiuroids from the New Caledonian region, Memoirs of Museum Victoria 73, pp. 47-57 : 52-54

Ophiodaphne impellera sp nov

Fig. 3

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

4F1FE97F-6B95-40AE-BDA1-092DED147E52

Type material. -- New Caledonia. BIOCAL: stn CP23, Sud ouest, 22° 45.8'S, 166° 20.33'E, 2040 m, 28 Aug 1985, holotype ( MNHN IE.2013.16004) . -- paratype, same locality ( MNHN IE.2013.16005)

Description. Disc 5.5 mm diameter, rounded pentagonal in outline; arms emerging from underneath the disc, at least 2.5 times d.d. (all broken). Disc completely covered in rugose scales. Radial shields 0.31 times d.d., D-shaped to pentagonal, with an acute proximal angle, straight to slightly convex adradial margin, convex abradial margin, and rounded distal edge, contiguous for distal half of length but separated proximally by 2 small disc plates, rugose surface. The centre of the disc is dominated by the primary plates with small intercalary plates at their corners, primary plates with thickened borders and tuberculate centre. Interradius with several overlapping plates, one or two plates wide proximally, then becoming more numerous near the margin, large plates with thickened distal edge, smaller marginal plates particularly rugose. A row of small plates border the radial shields distally over the arm. Ventral surface covered in thin flat, circular scales, persisting to oral shields.

A pair of pointed papillae at each jaw apex; 3-4 oral papillae on each jaw side, the proximal one wide and rim-like, pointed proximally (probably the first oral tentacle or buccal scale); the next 2 papillae squarish with rounded corners, the outer of the 2 slightly larger, sometimes a tiny scale is present either distally at the interstice of the oral and first ventral arm plate, protecting the second oral tentacle pore, or between the first and second oral papillae. Ventral surface of the oral plates triangular in shape, meeting broadly within, beaded surface, the pair of oral plates forming a wide obtuse shaped jaw. Teeth twice as wide as long with a broad enamelled margin. Oral shields roughly diamondshaped, wide as long, with an obtuse proximal angle and rounded to lobed distal margin, acute lateral angles. Madreporite twice as large as other shields. Adoral shields tumid, wider than oral shield, trapezoid, widest radially, broadly contiguous interradially. Bursal slit extends to near disc margin, genital plates obscured.

Dorsal arm plates twice as wide as long, with an obtuse proximal angle, convex distal margin and rounded lateral angles, always separate, distal section of the plate with slightly tuberculate surface. Lateral arm plates beaded, meeting above and below arm, except basally where there is a small decalcified area between the ventral arm plates. Arm spine articulation formed from 2 parallel ridges, orientated radially. First ventral arm plate rounded triangular with a curved distal and obtuse proximal angle, forming distal margin to relatively wide oral cavity between jaws. Second to fourth plates twice as long as wide, roughly pentagonal with a straight to slightly convex distal edge, rounded distolateral angles, straight sides and convergent proximal edges that form an obtuse angle on the midline. The mid of the distal edge and the obtuse proximal angle can be produced into a small lobe that partially fills the decalcified area. Plates becoming progressively more triangular as the lateral edges shorten, becoming longer than wide distally, separate at first, becoming just contiguous distally. Three arm spines, rounded in cross section, tapering to a blunt tip, subequal, less than a segment in length basally, with middle spine slightly thickened. Uppermost spine reduced in size after basal segments, becoming absent after mid-arm. Lowermost spine becoming bottle-shaped with a narrow neck, which becomes curved, pseudo hook-shaped, on distal segments. Two small oval tentacle scales on first 4 segments, the one on the lateral arm plate larger than the one on the ventral arm plate, incompletely covering the pore. The smaller scale can be absent on the basal segments and is never present after the fourth.

Colour (dry): white.

Paratype 5.0 mm d.d. With similar morphology. Only 3 oral papillae, sometimes irregular in shape or position. Madreporite with rugose surface. Only 2 arm spines after the first few segments.

Distribution. New Caledonia (2040 m)

Remarks. These specimens have the two apical papillae and arm spine articulations characteristic of the Amphiuridae (A.M. Clark 1970; Martynov 2010). Within that family we provisionally place them in the genus Ophiodaphne on the basis of similar oral frames, with oral shields smaller than the thick adoral shields which meet broadly within, arm plates and hooked distal arm spines. The large female specimens of the type species, Ophiodaphne formata ( Koehler, 1905) , also have three oral papillae, but differ in having spiniform apical papillae and teeth, up to six cylindrical arm spines, narrow quadrangular radial shields, one oval tentacle scale and fine smooth disc plates (see Guille 1981). Large females of the second species, Ophiodaphne scripta ( Koehler, 1904b) have a fused oral papilla with a minutely denticulate edge, fully contiguous D-shaped radial shields, small round disc plates marked by small grooves, a single wide tentacle scale, and several hook-shaped arm spines distally (see Cherbonnier & Guille 1978). In both previously-described species, the male is a dwarf that is frequently found clinging to the oral surface of the female, and they are generally found commensal with sand dollars ( Tominaga et al. 2004) or (rarely) crinoids ( Cherbonnier & Guille 1978). We refrained from dissecting the two known dry specimens of the new species and thus cannot determine their gender. Nor is there any information that these specimens were found in association with sea urchins or crinoids. In many ways the three species are quite morphologically diverse, and it is possible that the shared characters are convergent - perhaps adaptations to an epizoic lifestyle. The new species was found considerably deeper than the other two (0-630 m) which are widely distributed across the Indo-west Pacific Ocean. However, we see no advantage to assigning the new species to a separate genus until we have adequate molecular evidence. As discussed under the next species, further study is required to determine what characters are useful to define genera within the Amphiuridae .

The mouth parts of Ophiodaphne formata and O. scripta are quite derived and there has been some debate whether they (and the similar sexually-dimorphic genus Ophiosphaera ) are better placed within the Amphiuridae or Ophiactidae . Martynov (2010) however, found that both genera had arm spine articulations that are conclusively of the amphiurid type.

Etymology. Named after the similar-looking impeller water pump that failed on TOH’s attempted crossing of Bass Strait on the yacht Irene.