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.
As well, in certain species of shark (spiny dogfish), Squalus acanthias, it has been proven under controlled conditions that they will change their feeding behavior and prey type based on competition with other species.t has been reported that under controlled conditions the spiny dogfish can vary their feeding mechanisms or techniques depending upon whatever J MATE 7 Vol 5, No 2, 2012 Printed in Canada Competitive Feeding Between a Shark and Seal Figure 1: Competitive foraging by a spiny dogfish upon food captured by a harbor seal.