The slender sawtail catshark (Galeus gracilis) is a little-known species of catshark, part of the family Scyliorhinidae, endemic to northern Australia. It is found over the continental slope in on water. Growing to long, this shark has a slim gray body with four dark saddle markings below the dorsal fins and on the caudal fin, as well as a prominent crest of enlarged dermal denticles along the dorsal edge of the caudal fin. The slender sawtail catshark is not valued by fisheries but is taken as bycatch. The International Union for Conservation of Nature (IUCN) presently lacks enough information to assess its conservation status. Taxonomy and phylogeny Leonard Compagno and John Stevens described the slender sawtail catshark in a 1993 issue of the scientific journal Records of the Australian Museum. They gave it the specific epithet gracilis, meaning "slender" in Latin; previously, the species had been provisionally termed Galeus sp. A. The type specimen is a long adult female, caught in January 1988 north of Melville Island, Northern Territory. Within the genus, G. gracilis appears to be closely related to G. eastmani, G. longirostris, and G. nipponensis. A 2005 phylogenetic analysis, based on mitochondrial and nuclear DNA, reported that this species, G. eastmani, and G. sauteri formed a clade apart from G. melastomus and G. murinus. Description A small species growing to at least long, the slender sawtail catshark has a slim body with a nearly cylindrical cross-section, and a short, narrow head with a rounded snout. The eyes are horizontally oval and equipped with rudimentary nictitating membranes (protective third eyelids). Below each eye is a thin ridge, and behind is a tiny spiracle. The nostrils are divided by small, triangular flaps of skin in front. The mouth forms a wide arch and bears moderately long furrows around the corners. The teeth are small and closely set, numbering 54–57 rows in the upper jaw and 54–62 rows in the lower jaw. Each tooth has a narrow central cusp usually flanked by one, occasionally two small cusplets on either side. The teeth of males are slightly larger and longer than those of females. There are five pairs of gill slits, with the fourth and fifth pairs over the pectoral fin bases. The first dorsal fin slightly exceeds the second in size and originates over the midpoint of the pelvic fin bases. The second dorsal fin is positioned over the last third