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
Ferreira's spiny tree-rat in 1817, Anselme Gaëtan Desmarest described the species based on this specimen housed in the National Museum of Natural History (France) of Paris. Using ancient DNA technology, a portion of the mitochondrial cytochrome b gene has been sequenced from a small skin fragment of this holotype. DNA sequence comparisons then suggested that the specimen was originally obtained in eastern Amazonia north of the Amazon River, most likely in the Brazilian state of Amapá. Ferreira's spiny tree-rat Ferreira's spiny tree-rat, "Mesomys hispidus", is a spiny rat species from South America. It is found in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana,