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.
Description: Pupfish are ray-finned fish with have striking coloration. The Devils Hole pupfish (Cyprinodon diabolis), for example, is bright blue with purplish accents.The White Sands pupfish has yellow and orange fins. Size: Most pupfish are very small, some less than an inch in length.Diet: Pupfish feed on algae, plants, aquatic invertebrates, and insects.ife History and Reproduction: The Devils Hole pupfish lives in a relatively constant habitat, so it can breed year round. The mating system is polygynous, and males may prevent other males from breeding with a female. When larvae hatch, they are less than a centimeter long.