Sclerothyone obunca Thandar & Arumugam 2022, comb. nov.
Creators: name: Thandar, A. S.
name: Arumugam, P.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Holothuroidea
Dendrochirotida
Sclerodactylidae
Sclerothyone
Sclerothyone obunca

description: Sclerothyone obunca (Lampert, 1885) comb. nov.
Another species considered by Arumugam (2011) as belonging to Sclerothyone is Havelockia obunca (Lampert, 1885). Lampert placed this species in Cucumaria but provided a rather vague description without even mentioning the number of specimens he had examined. He described the holotype as 30 mm long and the calcareous ring as 3 mm high, but illustrated only a single ossicle, presumably from the body wall. Mitsukuri (1912) described two specimens from Asamushi (Japan), which he claimed to belong to Cucumaria obunca (Lampert, 1885), but neither described nor illustrated the calcareous ring or any ossicles. Long after Östergren’s death, Heding (in Östergren et al., 1938) compiled Östergren’s incomplete works, in which he presented an illustration of the calcareous ring and ossicles of this species but without a description or any locality or other data. We, therefore, opine that the illustration was from Östergren’s incomplete work on this species, presumably from the type material from the Copenhagen/Stuttagart Museums (as there were only two records of the species to that date [that of Lampert (1885) and Mitsukuri (1912)]. According to the curator at the Copenhagen Museum (pers. comm.), the holotype of C. obunca appears to be lost and attempts to locate it at other museums were unsuccessful. Mitsukuri (1912) dubiously assigned two of his specimens to this species, but without illustrations, but attempts to locate these specimens also proved unsuccessful. Mitsukuri (1912) stated that in some respects his specimens resembled Cucumaria chronhjelmi Théel, 1886 but with which Deichmann (1938) disagreed and described Mitsukuri’s (not Théel’s C. chronhjelmi) as Eupentacta pseudoquinquesemita? with some doubt, while designating Selenka’s (1867) Cucumaria quinquesemita as type species of her new genus Eupentacta (accessed WoRMS, October 2022). She, further, declared that both species are North-East Pacific in distribution, perhaps extending to Japan. In addition, Deichmann (1938) stated that Selenka’s record of E. quinquesemita from South Carolina, proved on examination to be referable to Pentamera pulcherrima (Ayres), thus clearing up a puzzling distribution range.
Panning (1949), in his revision of the Cucumariidae, transferred Lampert’s C. obunca to Pentathyone after synonymizing the latter with Havelockia. Thus, this species currently remains in Havelockia (WoRMS, accessed October 2022), despite the fact that the tube feet are restricted to the ambulacra. Hence, this species, on the basis of Martin & Tavares’ amendment of the diagnosis of the family, is now also transferred to Sclerothyone, despite the presence of shorter posterior processes to the radial plates (Figure 1F). It perhaps belongs to a new genus within the Sclerothyonidae, but because of its restriction of the podia to the ambulacra and the resemblance of its ossicles to those of other species of Sclerothyone, it is here also referred to this genus. Despite the presence of 2-pillared tables in the body wall (Figure 1G) and introvert (Fig. 1I), S. obunca differs from other species within Sclerothyone in possessing peculiar, elongated tables in the tentacles (Fig. 1H).
Another specimen collected from the type locality in 1896 and identified as Pentathyone obunca (Lampert) (USNM 30629), appears to have dried up prior to preservation, with the internal anatomy difficult to discern and the body wall and tube feet ossicles corroded. However, its tube feet are not restricted to the ambulacra. Therefore, whether this specimen is really S. obunca or another species is open to question.
description: Published as part of Thandar, A. S. & Arumugam, P., 2022, Referral of Thyone neofusus Deichmann, 1941, Thyone adinopoda (Pawson & Miller, 1981 and Havelockia obunca (Lampert, 1885) to the genus Sclerothyone Thandar, 1990, and a replacement name for the preoccupied genus Neothyone Deichmann, 1941 (Echinodermata: Holothuroidea: Dendrochirotida), pp. 65-71 in Zootaxa 5219 (1) on page 68, DOI: 10.11646/zootaxa.5219.1.3, http://zenodo.org/record/7408120