Echinorhinus, De Blainville, 1816

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 : 227

Echinorhinus sp. 1

( Figs. 5A , 17 A–D)

Three bramble shark specimens (SL-90, SL-108, and SL-109) were examined at the landing site of the deep-sea longline fishery in Mutur in the Eastern Province. The upper and lower jaws of SL-90 have been deposited in the BRT Ichthyology Collection (BRT-I 0022). The morphology of these specimens is consistent with that of Echinorhinus brucus (Bonnaterre) , especially in their possession of large, irregularly scattered thorn-like denticles and characteristic teeth with a single main laterally-directed cusp and one to two cusplets. However, our molecular work calls this identification into question. The specimens formed a tight cluster in the tree resulting from Neighbor-Joining analysis of NADH2 data with the reference specimen ( JQ400114 ) of an undescribed species, referred to by Naylor et al. (2012b) as Echinorhinus sp. 1, from the Gulf of Oman. These four specimens differed from one another by 0–2 bp. In contrast, the specimens from Sri Lanka differed from our reference specimen of E. brucus ( JQ519170 ) from the Gulf of Mexico by 52–53 bp. What is even more interesting is that, despite their possession of conspicuous, large, thorn-like denticles as seen in E. brucus , the specimens from Sri Lanka clustered more closely with the reference specimen of Echinorhinus cookei Pietschmann ( JQ519016 )—a species known to lack enlarged thorns—but differed from this specimen by 48–50 bp. Although more detailed morphological work remains to be done, our results suggest that the bramble shark in Sri Lanka may represent an undescribed species that also appears to occur in the Gulf of Oman.

It seems likely this is the taxon currently referred to as E. brucus in Sri Lanka (e.g., De Silva 1984 –1985, 2006, 2015; De Bruin et al. 1995; Morón et al. 1998; Joseph 1999).

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 17. Echinorhinus sp. 1 (Echinorhinidae) (A–D), Hexanchus griseus (Hexanchidae) (E–H), and Chiloscyllium sp. 1 (Hemiscylliidae) (I–K). A. Lateral view of female (SL-108). B. Ventral view of head of female (SL-108). C. Teeth of upper jaw of female (SL-108). D. Teeth of lower jaw of female (SL-108). E. Lateral view of immature male (SL-106). F. Ventral view of head of female (SL-91). G. Teeth of upper jaw of female (SL-91). H. Teeth of lower jaw of female (SL-91). I. Lateral view of mature male. J. Ventral view of head of mature male (SL-59). K. Dorsal view of head and trunk of mature male (SL-59).