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
Western Saharan spiny mouse Formerly considered conspecific with Cairo spiny mouse "Acomys cahirinus" but there are differences in the number of chromosomes. It may be conspecific with Chudeau's spiny mouse "Acomys chudeaui" from Morocco and, if that is the case, then the correct species name is "Acomys chudeaui" as this name has precedence. Western Saharan spiny mouse The Western Saharan spiny mouse or Aïr spiny mouse ("Acomys airensis") is a species of small, insectivorous rodent in the family Muridae found arid regions of western Africa. The Western Saharan spiny mouse is a small mouse with large ears, small eyes and a sharp snout. The