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Author: Capello, 1868

Field Marks:
A large, bulky, dark-brown, soft-bodied shark with elongated, catlike eyes and nictitating eyelids, large spiracles, a huge, wide, angular mouth that reaches behind eyes, very short labial furrows, numerous small cuspidate teeth in 200 or more rows in each jaw, two large spineless dorsal fins and an anal fin, a low, long, keel-like first dorsal fin on back, no precaudal pits, and a caudal fin without a strong ventral lobe or lateral undulations on its dorsal margin.

Diagnostic Features:
Head without laterally expanded blades; eyes elongated and slitlike, their lengths over 2 times the height; nictitating eyelids rudimentary; spiracles present and very large; anterior nasal flaps broadly angular, not barbel-like; internarial width about 2.8 times the nostril width; labial furrows very short; teeth small, with acute narrow cusps, lateral cusplets, and strong basal ledges and grooves, not bladelike and similar in both jaws; posterior teeth comblike; tooth rows very numerous, 202 to 294/258 to 335. Precaudal pits absent. First dorsal fin very large, low and formed as a rounded keel, about as long as caudal fin; first dorsal base on back with insertion just opposite pelvic origins and origin about opposite free rear tips of pectorals; midpoint of first dorsal base well in front of pelvic origins; pectoral fins with radials confined to bases of fins; ventral caudal lobe absent or very weak; no undulations or ripples in dorsal caudal margin. Neurocranium with supraorbital crests; vertebral centra without strong, wedge-shaped intermedial calcifications. Valvular intestine with a spiral valve of 17 turns. Colour plain except for darker fins. Development ovoviviparous.

Geographical Distribution:
Western North Atlantic: New York to New Jerscy. Eastern North Atlantic: Atlantic Slope off Iceland, France, Portugal, Madeira, Azores, Senegal, and Cape Verde Islands. Western Indian Ocean: Aldabra Islands group. Western Pacific: Japan and Taiwan Island. Central Pacific: Hawaiian Islands.

Habitat and Biology:
A big deepwater bottom-dwelling shark of the continental and insular slopes at depths from 200 to 1500 m; occasionally wandering onto continental shelves, even in shallow water (possibly abnormally). The large body cavity, soft fins, and soft skin and musculature of this shark suggests that it is relatively inactive and sluggish, and can hover off the bottom at virtually neutral buoyancy.

Ovoviviparous, with litters of 2 to possibly 4 young. At 8 to 32 cm length embryos have large yolk sacs with abundant yolk, but the considerably larger size attained by term fetuses, the small litter size of this shark, and the immense number of eggs produced by adult females (estimated at 20 000 in one ovary for a 280 cm adult female) led Forster et al. (1970) to suggest that this shark may have oophagy or uterine cannibalism as in lamnoid sharks. This hypothesis remains unproven, however.

Feeding habits little-known, once photographed in deep water in the Indian Ocean eating a bony fish used as bait on the camera. Probably feeds on a variety of deepwater bony fishes, elasmobranchs and invertebrates. Its teeth are small but sharp-cusped, and its mouth is very large, which may allow prey organisms of considerable size to be ingested.

Size:
Maximum 295 cm; adult males from 200 to 269 cm, adult females reported from 212 to 295 cm; size at birth between 70 and 85 cm.

Interest to Fisheries:
Minimal, taken on deep-set longlines and less commonly in bottom trawls. Utilization not reported.

Type material:
Holotype: Museu Bocage, Lisbon, Portugal, 2310 mm adult male, lost in fire that recently destroyed this museum. Type Locality: Setubal, Portugal.

False catshark (Pseudotriakis microdon)