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.
But it is on its own terms that the Spiny Dogfish really excels. This species is basically a deep-sea shark that has secondarily re-invaded shallow, near-shore waters. The Spiny Dogfish seems to prefer cold waters between 45 and 59 degrees Fahrenheit (7 and 15 degrees Celsius).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.