Ophiolimna phragma ( Ziesenhenne, 1940 ) Granja-Fernández & Hendrickx & Rangel-Solís & López-Pérez, 2023

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 : 40-42

Ophiolimna phragma ( Ziesenhenne, 1940) new combination

Fig. 11G‒L

Ophiacantha phragma Ziesenhenne, 1940: 11‒13 , pl. 2 figs. 4‒6.— Boolotian & Leighton 1966: 7, 10, fig. 29.

Material examined. One individual at one station. TALUD XVIB, Sta. 28, 1 ind. (ICML-EMU-11682).

Comparative material. Ophiacantha phragma Ziesenhenne, 1940 , holotype, 1 ind.: LACM 597.7 . Paratypes, 23 ind.: LACM 597.3 , LACM 597.6 , LACM 597.8 , LACM 597.9 , LACM 597.10 , LACM 597.11 , LACM 597.12 , LACM 597.13 , LACM 597.14 , LACM 597.15 , LACM 597.16 (Supplementary file 2).

Description (ICML-EMU-11682). DD = 6 mm. Disc rounded. Dorsal disc densely covered by granules and scattered elongated spines. Primary plates not evident. RS covered by granules and spines ( Fig. 11G ). Ventral interradii covered by granules, smaller than dorsal granules ( Fig. 11H ). OSh broader than long, triangular with rounded edges, granules distally. Madreporite larger than OSh, with a central rounded depression. AdSh longer than broad, very slender, meeting in front of OSh. Jaws bearing 5‒6 papillae at each side; AdShSp rounded; LOPa 3‒4, first LOPa similar in shape to AdShSp but smaller, rest elongated and pointed; IPa elongated, pointed. vT wider than oral papillae ( Fig. 11I ). Arms slender. First DAP covered by granules; subsequent DAP longer than broad, hexagonal with rounded distal edge, meeting. Longitudinal swollen keel along DAP ( Fig. 11J ). First VAP broader than long, rhombic, smaller than rest. Second to fourth VAP broader than long; subsequent VAP longer than broad, triangular with concave distal edge, meeting excepting distally. LAP striated. LAP with 6‒7 ArSp, large (almost two arm segments in length), slender, blunt, dorsalmost largest, ventralmost shortest. First 2‒3 tentacle pores with two TSc; subsequent pores with one oval TSc ( Fig. 11K ). Color pattern in dorsal disc and arms brown ( Fig. 11G, J, L ), ventral side beige (ethanol preservation) ( Fig. 11H ).

Habitat and distribution. California, USA, Mexico, Costa Rica, Panama, Colombia, Ecuador, and the Galapagos Islands; 13‒ 1,532 m depth, muddy and sandy substrates, gravel, and coralline bottoms ( Ziesenhenne 1940; Solís-Marín et al. 2013; see Remarks). The material examined was collected off western Baja California; 1,461 ‒1,532 m depth.

Remarks. The genus Ophiacantha is characterized by uncovered bar-like radial shields ( Matsumoto 1917), but Ophiacantha phragma , as originally described, has radial shields covered by granules and spines. Our revision of O. phragma , including a detailed examination of the holotype and paratypes, clearly indicated that it belongs to Ophiolimna due to the following characters: 1) a disc densely covered with numerous granules and few spines, 2) distalmost papillae broad, rounded, and operculiform, 3) the junction area of the adoral shields and the edges of the oral shield covered by granules, 4) a single broad tentacle scale, and 5) striated lateral arm plates ( O’Hara & Stöhr 2006; Martynov 2010). Therefore, it is herein proposed to assign this species to the genus Ophiolimna (new combination). Ophiolimna phragma is very similar to O. bairdi , but the following characteristics help to easily distinguish them from one another (comparing specimens with a similar size, DD = 6 mm): 1) dorsal arm plates triangular, as long as wide in O. bairdi vs. hexagonal, longer than wide (2‒3 times) in O. phragma , 2) adoral shields conspicuous in O. bairdi vs. inconspicuous, hardly noticeable in O. phragma , 3) distalmost oral papilla of much larger size in O. bairdi , and 4) one tentacle scale in O. bairdi vs. first 1‒8 segments with two tentacle scales and then with one tentacle scale in O. phragma . The genus Ophiolimna currently includes seven species ( Stöhr et al. 2022) of which O. bairdi and O. phragma are the two representatives for the eastern tropical Pacific. The previously deepest record for O. phragma was from 644 m depth ( Maluf 1988; as Ophiacantha phragma ), but during the TALUD cruises one specimen was collected as deep as 1,532 m.

Figures

FIGURE 11. Ophiolimna bairdi (Lyman, 1883) (ICML-EMU-11211, DD = 10.8 mm). A, Dorsal disc; B, Ventral disc; C, Mouth; D, Dorsal arm; E, Ventral arm; F, Dorsal view. Ophiolimna phragma (Ziesenhenne, 1940) (ICML-EMU-11682, DD = 6 mm). G, Dorsal disc; H, Ventral disc; I, Mouth; J, Dorsal arm; K, Ventral arm; L, Dorsal view.