Marine invertebrates at various trophic levels point at an important role in many ecosystems. Echinoderms (Greek for "spiny skin") is a phylum which contains only marine invertebrates. The adults are recognizable by their radial symmetry (usually five-point) and include starfish, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest grouping of deuterostomes (a superphylum), after the chordates (which include the vertebrates, such as birds, fishes, mammals, and reptiles). Echinoderms are unique among
Western Saharan spiny mouse 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 fur on its back is tawny, each hair being grey at the base with a rufous sub-terminal band and a grey tip. It takes its name from a line of spiny hairs on the posterior part of the back, in older mice the spiny hairs spread forwards along the