Amphipholizona H.L. Clark, 1915

Gondim, Anne Isabelley, Christoffersen, Martin Lindsey, Dias, Thelma Lúcia Pereira & Solís-Marín, Francisco Alonso, 2016, Taxonomic status of the genera Amphipholizona H. L. Clark, 1915 (Ophiuroidea, Ophiolepididae) and Amphigyptis Nielsen, 1932 (Hemieuryalidae): systematic placement and synonymy, Zootaxa 4097 (3), pp. 381-395 : 383-384

Genus Amphipholizona H.L. Clark, 1915

Amphipholizona H.L. Clark, 1915: 335 .― Fell, 1960: 34 (Key).― Albuquerque, 1986: 257. Amphigyptis Nielsen, 1932: 306 .― Fell, 1960: 12 (Key).― Solís-Marín et al., 2005: 128.

Type-species. Amphipholizona delicata H.L. Clark 1915

Diagnosis. Disc circular, covered by few, flat and polygonal plates. Bursal slits short, localized on lateral margin of oral shields. Abradial genital plate long. Abradial genital plate scale-like. Oral shields small and diamond-shaped. Adoral shields large, swollen, as wide as long, broadly united proximally. Two oral papillae, distalmost opercular. Infradental papillae rectangular. Stereom of arm plates simple and fine, and ornamented with minute thorns. Six arm spines, thin, dorsal longest. Arm spine articulation formed by two lip-shaped parallel ridges of the same length, slightly curved, separated at both ends, between them two large openings of nearly equal size (muscle and nerve opening). Tentacle pore large. Tentacle scale absent or restricted to first five arm segments.

Remarks. H.L. Clark (1915) erected the genus Amphipholizona based on 19 specimens collected off Barbados. According to him, his new genus showed a remarkable combination of characters between both, the oral surface being very amphiurid-like, while the dorsal side of the disc was Ophiolepis -like (as Ophiozona Lyman, 1865 ). However, the author preferred to put this genus in the family Ophiolepididae , in view of the characters shown by the disc and the internal plates. Fell (1960), in his synoptic key to Ophiuroidea, was the first author to place Amphipholizona in the subfamily Ophiolepidinae Matsumoto, 1915. However, Amphipholizona does not fit into any of the two groups of Ophiolepidinae proposed by Matsumoto (1915). Tommasi (1974), on the other hand, classified the present genus in the subfamily Ophiolepidinae of the Amphiuridae . Considering that Ophiolepidinae had never been placed within Amphiuridae , we believe that Tommasi’s (1974) classification was an error. Borrero- Pérez et al. (2008) classified this genus in the Ophiuridae Lyman, 1865 , which they considered a synonym of Ophiolepididae .

Seventeen years after the description of Amphipholizona, Nielsen (1932) described the monotypic genus Amphigyptis , on the basis of specimens collected in the Perlas Archipelago. This author stressed that the new genus presented the strongest likeness to Ophiomoeris Koehler, 1904 (as Ophiogyptis Koehler, 1904 ), and thus his new genus, together with Ophiomoeris and Ophiochondrus Lyman, 1869 , formed a group within Hemieuryalidae , which were named Ophiochondrinae Verrill, 1899 . However, Nielsen (1932) was not sure about the systematic placement of the genus. He found it impossible to decide if Amphigyptis was an amphiurid with the shape of an hemieuryalid or a hemieuryalid which has the paired infradental papillae characteristic of Amphiuridae . Nevertheless, the author preferred to place the new genus within the family Hemieuryalidae . Thomas (1966), in his revision of the tropical American species of Amphipholis , suggested that Amphigyptis was a synonym of Amphipholis (as Axiognathus Thomas, 1966 ). We do not agree with this author, because Amphigyptis does not present the diagnostic characters of Amphipholis . These genera have a very similar pattern of oral papillae and some species of Amphipholis have one or no tentacle scales, but differ in all remaining traits.

In this study, we compared specimens of Amphipholizona delicata and Amphigyptis perplexa and concluded that the genera must be synonymized, as no significant difference was found that could justify their maintenance as distinct taxa. Among the several characters that suggest they represent a single genus, includes the shape and covering pattern of the disc, the similar oral frame plates, and the similar morphology of the lateral arm plate. According to Thuy & Stöhr (2011), congeneric species generally share greater similarities in the lateral arm plate morphology than with species of other genera. According to the priority principle, article 23 of the Code of Zoological Nomenclature, Amphipholizona must be considered the valid name for the genus. Amphigyptis is a junior synonym of Amphipholizona .

On the basis of the present SEM study of genital plates, lateral arm plate, arm spine articulations, and vertebrae, Amphipholizona differs greatly from the families Ophiolepididae and Hemieuryalidae but shares several characters with Amphiuridae , particularly the oral structures and patterns of articulation of the arm spines. According to Martynov (2010), the type of arm spine articulation, in combination with some internal characters, such as the type of vertebrae and jaw plates, are essential for clarifying taxonomic and phylogenetic placements at different levels (from families to species) within the systematics of Ophiuroidea. Thus, the presence of zygospondylous vertebrae, infradental papillae, and arm spine articulations typical of amphiurids demonstrate that the previous placement of Amphipholizona was incorrect. We thus suggest transferring Amphipholizona to the family Amphiuridae .