Amphiophiura confecta ( Koehler, 1930 ) Koehler, 1930

Stöhr, Sabine, 2011, New records and new species of Ophiuroidea (Echinodermata) from Lifou, Loyalty Islands, New Caledonia, Zootaxa 3089, pp. 1-50 : 24-26

Amphiophiura confecta ( Koehler, 1930) new combination

Figure 10 A–I

Stegophiura confecta Koehler, 1930: 234 , pl. 19 figs 1, 2; Guille 1981: 449, pl. 8 fig. 46. Amphiophiura taranui McKnight, 1968: 20 –210, fig. 2. [new synonymy]

Material. Sta. 1461: 2 spms; sta. DW1650: 1 spm, sta. DW1650C: 2.

Description. In a specimen of 7.5 mm dd, disk high, dorsally covered by few large plates, among which the primary rosette is prominent, occupying most of the disk surface. Radial primary plates abut oval, contiguous radial shields. In each interradius a pentagonal proximal plate abutting two adjacent radial primaries, a smaller rectangular plate distally and a row of three smaller plates at the disk edge, the middle of them square, the left and right plate with convex sides. Radial shields slightly domed, robust, stereom with rough surface with large pores. Arm comb well developed, with spiniform papillae. Dorsal arm plates fan shaped, wider than long, contiguous, first plate overlapped by radial shields, microstructure finely porous. Lateral arm plates thick, protruding from arm, their microstructure similar to the radial shields. Arm spines three, two dorsal ones widely separated from each other, with wide base, abruptly constricted into an elongated point. Ventral spine conical, close to the single leaflike tentacle scale, both at the edge of the pore. All spines half as long as an arm joint. Spine articulation a large round hole with smooth patch at one edge.

Jaws with single small pointed apical papilla, a small round infradental papilla to either side of the dental plate, three to four wider than high, scale-like lateral papillae at oral plate. Second tentacle pore superficial, encircled by low wide scales, two along adoral shield, two on first ventral plate. Oral shield elongated drop-shaped, occupying two thirds of interradial space. Distal to it two smaller triangular plates and a large pentagonal plate, abutting the three interradial plates at the disk edge. These ventral interradial plates and distal edge of oral shield with transverse grooves. Bursal slits extend from adoral shields to disk edge, lined with large genital plate, bearing a row of spiniform papillae. Ventral arm plates tumid, wider than long, with proximal angle, distal edge convex, separated, on joint 3 and 4 with transverse grooves, farther out with holes.

Remarks. Amphiophiura is characterized by a high dorsal disk, covered with relatively few large scales among which the primary plates are clearly distinguishable, the presence of an arm comb, and stout, short arms. In these characters it is similar to Stegophiura and the boundaries between both genera are ill-defined. The difference between them is supposed to be in that the arms are widened at the base and tapering more rapidly in Stegophiura than in Amphiophiura . However, this character varies between the species placed in both genera ( Koehler 1922) and already Matsumoto (1915) remarked on the possible overlap between certain species placed in either genus. A more useful distinction appears to be the presence of two types of arm spines in Stegophiura , where in addition to regular spines a fringe of numerous small spines can be found along the dorsal part of the lateral plate edge. Since these secondary spines are lacking in A. confecta I propose to transfer it to Amphiophiura . A revision of these genera is obviously needed.

According to the images of the holotype ( McKnight 1968), A. taranui is conspecific with A. confecta . As McKnight (1968) commented, there is also some similarity with A. urbana ( Koehler, 1904) , but that species reaches twice the size of A. confecta and has more dorsal disk scales, which create a different pattern at the disk edge. Amphiophiura laudata Koehler, 1904 is of similar size to A. confecta , but has an additional circle of plates between primaries and radial shields and more plates on the ventral interradius.

Distribution. Type locality is Banda, Indonesia, at 100 m ( Koehler 1930). At Lifou the species was found at 100–260 m and it is a new record for New Caledonia.

Figures

FIGURE 10. SEM images, A – I, Amphiophiura confecta. A, dorsal aspect; B, interadial disk dorsolateral aspect; C, dorsal arm; D, lateral arm; E, ventral aspect; F, oral details; G, ventral arm; H, arm spine articulation on lateral plate; I, dorsal arm spine. J – O, Amphiophiura distincta. J, dorsal aspect; K, dorsal arm, L, ventral aspect; M, oral details; N, ventral arm; O, arm lateral aspect. Scale bars in millimetre.