Expandable dwarf species of shark

The Indian swellshark (Cephaloscyllium silasi) is a catshark belonging to the family Scyliorhinidae found in the north-central Indian Ocean. The Indian swellshark is a dwarf species and can expand its body by taking in air or water to make it appear larger to predators.


Family: Scyliorhinidae – Catsharks

Genus: Cephaloscyllium 

Species: silasi


Phylum– Chordata

Class– Chondrichthyles


Common NameGround Sharks

Family– Scyliorhinidae

Common NameCatsharks




Average Size and Length: The largest recorded was an adult male at 36 cm/1.2 feet.

Teeth and Jaw: The mouth is large and arched. The mouth width is 0.6 times the head length. Labial furrows are absent but a vestigial lower labial furrow may be present.

Head: The head is depressed, flattened and broad. The anterior nasal flaps are broadly triangular. There are ridges over the eyes. The eyes are dorsolateral and slit like, with a cat-like appearance.

Demographic, Distribution, Habitat, Environment and Range: The Indian swellshark can be found near Quilon, India in the north-central Indian Ocean (16° N and 10° N). There is another small swellshark that seems to inhabit this range, but it needs a species identification. They are found on the bottom on the uppermost continental slope. Specimens were collected at around 984 feet. They are a bathydemersal, deep-water species.

Diet: Stomach examined contains crustaceans and cephalopods.

Aesthetic Identification: The Indian swellshark is a dwarf species of shark. There is a pattern of seven moderately broad dark brown saddles on a light brown background. There is an obscure blotch over the pectoral inner margins. The ventral side is light brown without spots. There are no conspicuous light fin margins. The body is stout with an expanded belly. There are 5 gill slits dorsolaterally placed and the last two gill slits are over pectoral fins. The 1-3 gill slits are subequal in length, the 5th one is the smallest. The first dorsal fin is larger than the second dorsal fin. The first dorsal fin originates over the pelvic fin bases. The second dorsal fin is much smaller and originates over the anal fin.

Biology and Reproduction: They are oviparous. A 45 cm/1.5 foot female was found gravid and have two egg cases, one in each uterus, containing visible embryos of 8.51-8.62 cm with attached yolk sac.

Behavioral Traits, Sensing and Intelligence: The Indian swellshark can expand its body by taking in air or water to make it appear larger to predators in an attempt to frighten them.

Indian Swellshark Future and Conservation: There is not enough data to evaluate. They seem to be common among their small range.

Indian Swellshark Recorded Attacks on Humans: Not a threat to humans.