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
Broad-headed spiny rat Broad-headed spiny rat The broad-headed spiny rat ("Clyomys laticeps") is a spiny rat species from South America. The etymology of the species name is the Latin word "laticeps" meaning "wide-headed". The species has a head-body length that ranges from , with a tail long, and weigh between . They have short ears and limbs, and feet with powerful claws adapted for digging. The fur is interspersed with spines; it is grizzled reddish or yellowish and black over most of the body, and paler grey to almost white on the underparts. Broad-headed spiny rats are native to southern Brazil and eastern