Centrophorus cf. atromarginatus, Garman, 1913

Fernando, Daniel, Bown, Rosalind M. K., Tanna, Akshay, Gobiraj, Ramajeyam, Ralicki, Hannah, Jockusch, Elizabeth L., Ebert, David A., Jensen, Kirsten & Caira, Janine N., 2019, New insights into the identities of the elasmobranch fauna of Sri Lanka, Zootaxa 4585 (2), pp. 201-238 : 231

Centrophorus cf. atromarginatus

( Figs. 5E , 18 A–C)

Six specimens (SL-85, SL-86, SL-87, SL-88, SL-89, and SL-95) of the short-snout group of Centrophorus Müller & Henle species were examined from the deep-sea longline landing site in Mutur in the Eastern Province. Although definitive identification of many species of Centrophorus remains problematic (e.g., see Verissimio et al. 2014; White et al. 2017), these specimens do not conform to the description of any of the 12 valid species in the genus. A female specimen of this species has been deposited in the BRT Ichthyology Collection (SL-87; BRT-I 0021). In the tree resulting from the Neighbor-Joining analysis, these six specimens grouped in a tight cluster, differing from one another by 0–4 bp in NADH2 sequence. We have preliminary identified these specimens as Centrophorus cf. atromarginatus . The specimens most closely resemble Centrophorus atromarginatus Garman but appear to differ from this species in that the black coloration on the dorsal fins is not restricted to the posterior margins but covers the dorsal half of both fins. In addition, the pectoral fins lack black posterior margins, as does the upper lobe of the caudal fin. Examination of the holotype and voucher specimens of C. atromarginatus from throughout its current known distribution from Japan to the Gulf of Aden reveals some morphological variation, suggesting it may constitute a species complex (DAE, unpubl data). Unfortunately, NADH2 data for a confirmed reference specimen of C. atromarginatus were unavailable. Further comparison of regional specimens and generation of NADH2 data for specimens of C. atromarginatus from its type locality in Japan (see Eschmeyer et al. 2018) would be useful to confirm this lack of conspecificity. We have employed this name in recognition of the fact that these specimens may represent additional novelty in the genus.

Three species of Centrophorus have been reported from Sri Lanka: Centrophorus moluccensis Bleeker (e.g., Joseph, 1999; tentatively Ebert, 2013; De Silva, 2015), Centrophorus squamosus (Bonnaterre) (e.g., Morón et al. 1998; Weerakkody & Fernando 2000; De Silva 2006, 2015), and Centrophorus uyato Rafinesque (e.g., tentatively Morón et al. 1998; Joseph, 1999). This is one of the candidates for the species referred to in one or more of these reports, but in the absence of detailed images, this is difficult to assess.

Figures

FIGURE 5. Neighbor-Joining trees of p-distances based on 1,044 bp of aligned NADH2 sequence data for individual selachian genera or groups of genera. Taxon names are followed by country, host specimen number (in parentheses), and GenBank number. Outgroup taxa used in each analysis were omitted from the individual trees. Scale bar values indicate substitutions per site. Specimens deposited in the Blue Resources Trust Ichthyology Collection are indicted by stars (see text for details). A. Echinorhinidae. B. Hexanchidae. C. Lamniformes. D. Chiloscyllium (Hemiscylliidae). E. Centrophorus (Centrophoridae). F. Somniosidae/Oxynotidae (Somniosus omitted).

FIGURE 18. Centrophorus cf. atromarginatus (A–C) and Centrophorus uyato (D–F) (Centrophoridae). A. Lateral view of female (SL-87; BRT-I 0021). B. Ventral view of head of female (SL-87; BRT-I 0021). C. Denticles on left side below dorsal fin of female (SL-87; BRT-I 0014). D. Lateral view of female (SL-96; BRT-I 0026). E. Ventral view of head of female (SL-96; BRT-I 0026). F. Denticles on left side below dorsal fin of female (SL-96; BRT-I 0026).