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
Eastern spiny mouse species is nocturnal, avoiding the heat of the day and foraging at night for seeds, and sometimes insects and grasses. It is a sociable animal and lives in small groups. Females become mature at about two months of age and can produce litters of up to five young after a gestation period of about 42 days. Another female in the family group may help with care of the young, which are weaned after about a fortnight. Its spiny hair may help to prevent predation, perhaps making the animal harder to swallow, and this mouse is also capable of shedding its