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.
Lionfish are a marine species that are primarily red, brown and white and has a striped, zebra-like appearance. While there are two distinct but visually identical species found in their non-native range, about 97 percent are red lionfish. They grow to about 12-15 inches in length; however they have been noted to be larger in areas where they are not indigenous, exceeding 18 inches.