A new deep‐water chimaerid species, Hydrolagus lusitanicus n. sp., from off mainland Portugal with a proposal of a new identification key for the genus Hydrolagus(Holocephali: Chimaeridae) in the north‐east Atlantic

A new chimaerid species closely related to Hydrolagus pallidus is described from 13 specimens captured on the Portuguese continental slope (north-east Atlantic) by commercial longliners at depths of c. 1600 m. The new species is large-bodied with a rose to light brown body colouration. Hydrolagus lusitanicus n.sp. presents a combination of external morphological characters that allow it to be clearly differentiated from its congeners, in particular, the ratios of pectoral fin length: pectoral fin width and pelvic fin length: pelvic fin width: in having a serrated posterior edge of the dorsal spine; a high number of ridges in the dental plates. Additionally in males, there are differences on the shape and number of hooks in the frontal tenacula, on the number of spines in the prepelvic tenacula and on the length of the pectoral fin margin.