Raninidae is a family of unusual crabs, taken by most scientists to be quite primitive. These animals closely resemble the (unrelated) mole crabs, due to parallel evolution or evolutionary relay. In both groups, the claws are modified into tools for digging, and the body is a rounded shape that is easy to bury in sand. Unlike most other true crabs, the abdomens of raninids are not curled under the cephalothorax. Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Bilateria Acoelomorpha Orthonectida Rhombozoa ? Myxozoa Superphylum Deuterostomia     Chordata (vertebrates, etc. ... Subphyla and Classes Subphylum Trilobitomorpha Trilobita - Trilobites (extinct) Subphylum Chelicerata Arachnida - Spiders, Scorpions, etc. ... Orders Not necessarily a complete list: Leptostraca Stomatopoda Bathynellacea Thermosbaenacea Mysidacea Cumacea Amphipoda Isopoda Tanaidacea Euphausiacea Amphionidacea Decapoda Peracarida The Malacostraca are the largest subgroup of crustaceans, and include most of the animals that non-experts recognise as crustaceans, including the decapods (such as crabs, mole crabs, lobsters and true... Suborders Either suborders: Natantia Reptantia or suborders: Dendrobranchiata Pleocyemata The decapods or Decapoda are a group of crustaceans within the class Malacostraca. ... Infraorders Caridea Stenopodidea Reptantia, divided into: Polychelida Achelata Glypheoidea Astacidea Thalassinidea Anomala Brachyura Pleocyemata is a sub-order of decapod crustaceans, erected by Martin Burkenroad in 1963. ... Sections Dromiacea Raninoida Heterotremata Thoracotremata The term crab is sometimes applied to several different groups of short (nose to tail) decapods with thick exoskeletons, but only members of the Brachyura are true crabs; other taxa, such as hermit crabs, porcelain crabs, king crabs, and horseshoe crabs are, despite superficial similarities... Sections Dromiacea Raninoida Heterotremata Thoracotremata The term crab is sometimes applied to several different groups of short (nose to tail) decapods with thick exoskeletons, but only members of the Brachyura are true crabs; other taxa, such as hermit crabs, porcelain crabs, king crabs, and horseshoe crabs are, despite superficial similarities... The word primitive can refer to: primitive art and Primitivism (art) primitive (biology) primitive (computer science) primitive (linguistics) primitive (mathematics) primitive (ontology) Primitive (song) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Binomial name Emerita talpoida Say, 1817 Mole crabs (Emerita talpoida and a number of related species) are clawless oval-shaped crustaceans found on the Atlantic coast of North America. ... In evolutionary biology, parallel evolution occurs when two independent species evolve together at the same time in the same ecospace and acquire similar characteristics. ... The abdomen (from the Latin word meaning belly) is the part of the body between the pelvis and the thorax. ... The cephalothorax is an anatomical term used of arachnid and malacostracan arthropods for the first major body section. ...