SLENDER SAWTAIL CATSHARK

A catshark of northern Australia with a saw-like tail.

The Slender Sawtail catshark (Galeus gracilis) is a little-known species of catshark, belonging to the family Scyliorhinidae, endemic to northern Australia. It is found over the continental slope between 951-1,542 feet. They have 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. There is not enough data to evaluate this species, and they are apparently rare.

 

Family: Scyliorhinidae – Catsharks

Genus: Galeus 

Species: gracilis

Taxonomy:

Phylum– Chordata

Class– Chondrichthyles

OrderCarcharhiniformes

Common NameGround Sharks

Family– Scyliorhinidae

Common NameCatsharks

GenusGaleus

Speciesgracilis

Status: IUCN Red List DATA DEFICIENT

Average Size and Length: Mature males have been measured around 33 cm/1 foot. Mature females have been measured between 32-34 cm/1-1.1 foot. The maximum is at least 34 cm/1.1 foot.

Current Rare Mythical Sightings: 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 34 cm/1.1-foot-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.

Teeth and Jaw: 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. The inner lining of the mouth is dark grey.

Head: They have a short, narrow head with a rounded snout. The eyes are horizontally oval and equipped with nictitating membranes. 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.

Denticles: There is a crest of enlarged dermal denticles along the upper margin of the elongated tail. The body and fins are densely covered by tiny, overlapping dermal denticles. Each has a teardrop-shaped crown covered by small pits, and has a central ridge and typically three marginal teeth.

Tail: The caudal fin is narrow, with a small but distinct lower lobe and a ventral notch near the tip of the upper lobe.

Demographic, Distribution, Habitat, Environment and Range: The Slender Sawtail catshark is found in northern Australia from off Cape Cuvier and Port Hedland in Western Australia, off Melville Island off Northern Territory, and off Cape York in Queensland (10°S – 28°S), on the continental slope on or near the bottom between 951-1,542 feet. They are considered tropical bathydemersal.

Aesthetic Identification: The Slender Sawtail catshark is pale grey with four short dusky saddles. There is one beneath each dorsal din and two on the caudal fin. There are no predorsal markings. The ventral side is pale. They are small and slender in size and shape. The cross section is nearly cylindrical. 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 of the anal fin. The dorsal fins have rounded apexes. The short, wide pectoral fins are roughly triangular, with rounded corners. The pelvic and anal fins are long-based, low, and fairly angular. Adult males have long, tapering claspers, each with saw-like rows of denticles along the inner surface, and twisted tips. The anal fin base measures around 11% of the total length and exceeds or matches the distances between the anal fin and the pelvic and caudal fins.

Biology and Reproduction: Unknown, but more than likely oviparous.

Behavioral Traits, Sensing and Intelligence: Unknown.

Slender Sawtail Catshark Future and Conservation: There is not enough data to evaluate. They are apparently rare. They are probably taken as bycatch by trawlers, but there is no commercial interest.

Slender Sawtail Catshark Recorded Attacks on Humans: Not a threat to humans.