Evidence for the assignment of Dolichopteryx brachyrhynchus Parr to the genus Bathylychnops Cohen (Pisces, Opisthoproctidae)

The rare opisthoproctid genus Bathylychnops has previously been regarded as containing a single species, B. exilis , known from the transition waters of the eastern North Pacific and, questionably, from the North Atlantic. While the post‐larval and juvenile material reported here reaffirms the occurrence of the genus in the North Atlantic, and extends its range into the Indian Ocean, the lower vertebral and higher pelvic ray counts of specimens denies their reference to B. exilis. The systematics of the closely‐related genus Dolichopteryx are poorly known, distinction from Bathylychnops resting mainly upon Dolichopteryx having multiserial, as opposed to uniserial, vomerine teeth and lacking an accessory scleral lens to the eye. The species D. brachyrhynchus , known from a single, damaged Atlantic specimen, shows marked similarities with Bathylychnops in pigmentation and the relative positions of fins, anus and dorsal adipose fin, thereby differing from all its congeners. Although the holotype of D. brachyrhynchus lacks an accessory scleral lens, perhaps through damage, it has uniserial vomerine teeth. This latter character and those of similarities in meristics, morphometrics and pigmentation shown with Atlantic‐Indian Ocean Bathylychnops (contra B. exilis) are considered sufficient evidence to regard the two species as synonymous and hence transfer D. brachyrhynchus to the genus Bathylychnops.