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
Golden spiny mouse as between and under boulders, further shows that, if not for environmental factors, golden spiny mice would be nocturnal animals. Golden spiny mouse The golden spiny mouse ("Acomys russatus") gets its name from the reddish-orange spiny fur that covers its body from head to tail. This coarse, inflexible fur is thought to protect it from predation. Aside from the golden fur that covers its head and upper parts, its flanks are yellow and its underside is pale. It has gray legs with pale feet and black soles. It is also described as having a small, but distinct white spot under