Animal mesoderm forms by enterocoelic pouching, through invagination of the endoderm. The main deuterostome phyla are the Echinodermata and the Chordata. Echinoderms are exclusively marine and include starfish, sea urchins, and sea cucumbers. The chordates are dominated by the vertebrates (animals with backbones), which consist of fishes, amphibians, reptiles, birds, and mammals. The deuterostomes also include the Hemichordata (acorn worms). The Ecdysozoa are protostomes, named after their shared trait of ecdysis, growth by moulting. They include the largest animal phylum, the Arthropoda, which contains insects, spiders, crabs, and their kin. All of these have a body divided into repeating segments, typically
Pacific spiny dogfish half of the shark has a gray color with scattered white spots while the bottom half has a white/light gray color. The scales of the dogfish is composed of the same material of shark teeth called dermal denticles, making the skin very hard and durable. The skin of the sharks used to be used as sandpaper once dried to do woodwork or even be used as leather, once the denticles are removed. Lastly, the Pacific spiny dogfish has a set of teeth specialized for grinding instead of tearing by the teeth being flat with sharp edges. If any of the