Ophiochiton cf. fastigatus Lyman, 1878

Granja-Fernández, Rebeca, Hendrickx, Michel E., Rangel-Solís, Pedro Diego & López-Pérez, Andrés, 2023, Deep-sea Ophiuroidea (Echinodermata) collected during the TALUD cruises in western Mexico, Zootaxa 5259 (1), pp. 1-71 : 45

Ophiochiton cf. fastigatus Lyman, 1878

Fig. 13A‒F

Material examined. Six individuals at four stations. TALUD V, Sta. 19, 2 ind. (ICML-EMU-11176). TALUD XII, Sta. 30, 2 ind. (ICML-EMU-11177). TALUD XVIB, Sta. 5, 1 ind. (ICML-EMU-11677-A); Sta. 28, 1 ind. (ICML-EMU-11677-B).

Comparative material. Ophiochiton fastigatus Lyman, 1878 , syntype, 1 ind.: MCZ OPH- 1111. Ophiochiton carinatus Lu ̈tken & Mortensen, 1899 (junior synonym of O. fastigatus ), syntypes, 2 ind.: MCZ OPH- 1649, USNM 19554 (Supplementary file 2).

Description (ICML-EMU-11176). DD = 24 mm. Disc with constricted shape; a preservation artifact. Dorsal disc covered by fine scales, larger scales in disc margin and around RS. Primary plates rounded, very conspicuous, separated from each other by disc scales. RS triangular with rounded edges, separated by numerous scales ( Fig. 13A ). Ventral interradii covered by imbricated scales ( Fig. 13B ). OSh broader than long, triangular with rounded edges. Madreporite circular, larger than Osh. AdSh longer than broad, slender, distally triangular and wider, meeting in front of Osh. Jaws bearing 6‒7 papillae at each side, distalmost lanceolate and the largest, apical elongated. vT very pointed ( Fig. 13C ). Arms fragile. DAP broader than long, trapezoidal, contiguous ( Fig. 13D ). VAP broader than long, hexagonal, contiguous. DAP and VAP with a longitudinal middle keel along the arm. LAP with three ArSp, very elongated (approximately two arm segments in length), dorsalmost the longest. Tentacle pores with two TSc, adradial slender and elongated, abradial larger, rounded, flat ( Fig. 13E ). Color pattern in dorsal and ventral side light brown (ethanol preservation) ( Fig. 13A‒F ).

Habitat and distribution. The material examined was collected off western Baja California, in the south of the Gulf of California, and off Jalisco; 772‒ 1,532 m depth.

Remarks. The type material of Ophiochiton fastigatus from Japan (MCZ OPH-1111, DD = 15 mm) varied morphologically from the type material of Ophiochiton carinatus (MCZ OPH-1649, DD = 12 mm) in the following characters: RS size, length of adradial tentacle scale, shape of oral shields, shape and number of the oral papillae. The TALUD specimens are morphologically more similar to the type specimens of O. carinatus examined during this study (USNM 19554, DD = 23 mm), but they differ from the latter in the overall shape of the jaw. A thorough morphological examination and a molecular analysis are needed in order to determine if the observed morphological differences are linked to geographic or size variations or if they correspond to different species. Hendler (2018) mentioned that some members of the family Ophionereididae present five oral papillae at each side of the jaw (one LyOs, one AdShSp, one 2AdShSp, one BSc, and one IPa). However, all the specimens of Ophiochiton (type material and TALUD specimens) examined during this study showed 5‒7 oral papillae at each side of the jaw, thus suggesting that one or two papillae have not been accounted for and still lack a proper study. Therefore, more studies on the Ophionereididae jaw´s morphology are needed to understand the homology of these structures.

Figures

FIGURE 13. Ophiochiton cf. fastigatus Lyman, 1878 (ICML-EMU-11176, DD = 24 mm). A, Dorsal disc; B, Ventral disc; C, Mouth; D, Dorsal arm; E, Ventral arm; F, Dorsal view. Ophiopsila californica A.H. Clark, 1921 (ICML-EMU-11689, DD = 12 mm). G, Dorsal disc; H, Ventral disc; I, Mouth; J, Dorsal arm; K, Ventral arm; L, Dorsal view.