Marine life individuals per square meter and accounting for about 80% of all individual animals on earth, their diversity of life cycles, and their presence 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
Gracile Atlantic spiny rat is inappropriate because the word has nothing to do with the meaning or etymology of the Latin "gratiosus". A rival name, "graceful spiny-rat", is no better justified; ""gratiosus"" specifically means either "enjoying favour, favoured, beloved", or "showing favour, complaisant" "a favourite", or at best "gracious", not "graceful". No authority to date has proposed a better option than using the species name, "Trinomys gratiosus" in English. Gracile Atlantic spiny rat Trinomys gratiosus is a species in the mainly South American family Echimyidae, the spiny rats; it occurs in southeast Brazil from the south bank of the River Doce, Espirito Sante, southward