[2] A small shark with a laterally compressed body and a bulbous snout, this species has unusual adaptations that indicate a specialized lifestyle: its pectoral fins are paddle-like and may be used for propulsion, unlike other sharks and it has a pouch-like gland on its abdomen that emits clouds of luminescent blue fluid.

Phylogenetic analysis based on dentition indicates that the taillight shark is the most basal member of its family and is sister to the clade containing all other dalatiid species.

Although no definitive fossil remains have been found, the taillight shark may have evolved in the early Paleocene epoch (65.5–55.8 million years ago - Mya), as part of a larger adaptive radiation of dogfish sharks into midwater habitats.

However, whether the known specimens were captured near the sea bottom where the trawls operated or from midwater as the nets were being retrieved is unclear.

[1] The taillight shark is laterally compressed, with a long rounded snout and large oval eyes.

[7] On the belly in front of the cloaca is a pouch-like groove devoid of denticles and lined with a luminescent tissue formed into numerous, tightly packed papillae (nipple-like structures).

[5] The taillight shark is not caught significantly by any fishery, possibly due to its small size and habitat preferences.