In the thoracic region the intervertebral discs are relatively thin with respect to the vertebral bodies, and together with the presence of the ribs and sternum, their movement is limited.
The spiny dogfish, spurdog, mud shark, or piked dogfish, Squalus acanthias, is one of the best known species of the Squalidae (dogfish) family of sharks, which is part of the Squaliformes order.hile these common names may apply to several species, Squalus acanthias is distinguished by having two spines (one anterior to each dorsal fin) and lacks an anal fin. It is found mostly in shallow waters and further offshore in most parts of the world, especially in temperate waters.
Well armed as they are, Spiny Dogfishes are not free from various perils. In addition to humans, their predators include other sharks, large teleosts, seals, Killer Whales, and in one case, a Herring Gull that repeatedly dropped a small Spiny Dogfish onto the rocks until it stopped snapping, then ate it.art of the Spiny Dogfish s predatory secret is its teeth and jaws. Its teeth have oblique cusps with overlapping bases, forming a nearly continuous cutting edge. Spiny Dogfish jaws are short, transverse, and thickly muscled equipment for a powerful bite.