Soft like a sofa?

The False catshark or Sofa shark (Pseudotriakis microdon) is a species of shark belonging to the family Pseudotriakidae and is the sole member of its genus. It has a worldwide distribution, but a patchy one. It has most commonly been recorded close to the bottom in deep water over continental and insular slopes, at depths of 1,640–4,593 feet. It is a large shark with a heavy, but flabby body, and can be easily identified by its elongated, keel-like first dorsal fin.

Family: Pseudotriakidae – False Catsharks and Gollumsharks

Genus: Pseudotriakis 

Species: microdon


Phylum– Chordata

Class– Chondrichthyles


Common NameGround Sharks

Family– Pseudotriakidae

Common NameFalse Catsharks and Gollumsharks




Average Size and Length: They are born between 70-85 cm/2.3-2.8 feet. Mature males have been measured between 200-269 cm/6.5-8.8 feet and mature females between 212-295 cm/7-9.7 feet. The maximum recorded is 295 cm/9.7 feet in length.

Average Weight: It can weigh up to 276 pounds.

Current Rare Mythical Sightings: The False catshark was first described by Portuguese ichthyologist Félix de Brito Capelo in the Jornal do Sciências Mathemáticas, Physicas e Naturaes in 1868. He based his account on a 7.5-foot-long adult male caught off Setubal, Portugal. Brito Capelo thought the specimen resembled a member of the genus Triakis, except lacking a nictitating membrane (which now we know this shark does have a nictitating membrane). He assigned it to the new genus Pseudotriakis.

Teeth and Jaw: The mouth is large and angular and extends behind the eyes. The labial furrows are short. There are many small teeth, more than 200 rows per jaw. The teeth are arranged in straight lines in the upper jaw and diagonal lines in the lower jaw. Each tooth has a pointed central cusp flanked by one or two smaller cusplets on either side. They seem somewhat gummy and narrow.

Head: The head is broad. The snout is short. It has a bell shape when looked upon from the dorsal-ventral view. It is wedge-shaped laterally. The eyes are elongated and cat-like with nictitating membranes. There are short anterior nasal flaps. The spiracles are large and are comparable in size to the large eyes. The nostrils have large flaps of skin on their anterior rims.

Denticles: The dermal denticles are shaped like arrowheads with a central ridge and are sporadically placed on the skin.

Tail: The tail is stalky and soft. The caudal fin has a long upper lobe with a ventral notch near the tip, and an indistinct lower lobe.

Demographic, Distribution, Habitat, Environment and Range: The False catshark or Sofa shark has a patchy distribution (64°N – 48°S, 98°W – 153°W). They can be found world-wide from what researchers can tell, except they haven’t been found in the south Atlantic or eastern Pacific. In the western Atlantic, it has been reported from Canada, the United States, Cuba, and Brazil. In the eastern Atlantic, it is known from the waters of Iceland, France, Portugal, and Senegal, as well as the islands of Madeira, the Azores, the Canaries, and Cape Verde. Records from the Indian Ocean have come from off Madagascar, the Aldabra Group, Mauritius, Indonesia, and Australia. In the Pacific Ocean, it has been documented from Japan, Taiwan, Indonesia, the Coral Sea, New Zealand, and the Hawaiian Islands. They are found in deep water, on the seabed, on the continental and insular slopes between 656-6,201 feet, and occasionally on the continental shelves in shallower water near submarine canyons. It is most commonly found between 1,640–4,593 feet. They are considered bathydemersal.

Diet: They have been photographed feeding on fish in deep water. They are known scavengers of a variety of invertebrates and fish.

Aesthetic Identification: The False catshark or Sofa shark is un-patterned dark brown to blackish (darkening at the fins). However, a few individuals are light gray with irregular darker mottling made from fine dots. It is a large shark with a stalky, bulky soft body. The five pairs of gill slits are small. The first dorsal fin is long, low and keel like. The first dorsal fin originates over the pectoral fin rear tips and terminates over the pelvic fin origins. The second dorsal fin is much higher. The second dorsal fin originates ahead of the anal fin. The pectoral fins are small and rounded, with fin rays only near the base. Both the second dorsal fin and anal fin are positioned very close to the caudal fin.

Biology and Reproduction: The False catshark or Sofa shark has a large body cavity, soft fins, soft skin and soft musculature. This suggests they lead an inactive lifestyle and are also neutrally buoyant due to their large, oily liver.

They are ovoviviparous. They have 2 pups, possibly 4 pups per litter. They are possibly oophagous.

Pacific populations of the False catshark were once regarded as a separate species, P. acrales. However, morphological comparisons have failed to find any consistent differences between P. microdon and P. acrales, leading to the conclusion that there is only one species of False catshark (Yano, K.; Musick, J.A. (1992). “Comparison of morphometrics of Atlantic and Pacific specimens of the false catshark, Pseudotriakis microdon, with notes on stomach contents“. Copeia. 1992 (3): 877–886).

The closest relatives of the False catshark are Gollumsharks (genus Gollum). Pseudotriakis and Gollum share a number of morphological similarities. Phylogenetic analysis using protein-coding genes has found that the amount of genetic divergence between these taxa is less than that between some other shark species within the same genus. This result suggests that the many autapomorphies of the False catshark evolved relatively recently and supports the grouping of Pseudotriakis and Gollum together in the family Pseudotriakidae (López, J.A.; Ryburn, J.A.; Fedrigo, O.; Naylor, G.J.P. (2006). “Phylogeny of sharks of the family Triakidae (Carcharhiniformes) and its implications for the evolution of carcharhiniform placental viviparity“. Molecular Phylogenetics and Evolution. 40 (1): 50–60).

Behavioral Traits, Sensing and Intelligence: More than likely, they lead an inactive lifestyle.

Speed: More than likely they are sluggish in nature. They are neutrally buoyant.

False Catshark or Sofa Shark Future and Conservation: They are currently of least concern but are rare an uncommon in occurrence and have a very low reproductive rate, so this could become a concern in the future. It is an infrequent bycatch of longlines and bottom trawls. It has minimal economic value, though its meat, fins, and liver oil may be utilized. In Okinawa, its oil is traditionally used to seal the hulls of wooden fishing boats.

False Catshark or Sofa Shark Recorded Attacks on Humans: Not a threat to humans.