Raninidae is a family of unusual crabs, sometimes known as "frog crabs", on account of their frog-like appearance. They are taken by most scientists to be quite primitive among the true crabs. They closely resemble the (unrelated) mole crabs, due to parallel evolution or convergent evolution. 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.
The stalk-eyed mud crab, Macrophthalmus hirtipes, is a marine large-eyed crab of the family Macrophthalmidae, endemic to New Zealand including Campbell Island. It grows to around 30 millimetres (1.2 in) shell width. It is either the only species in the subgenus Hemiplax and the most basal species in the genus Macrophthalmus, or the only species in the sister genus Hemiplax.
Hemigrapsus crenulatus, the hairy-handed crab or papaka huruhuru, is a marine crab of the family Varunidae, endemic to the New Zealand coast, although a taxon in Chile may be conspecific. It is an intertidal species with semi-terrestrial tendencies. They are named by their characteristic setae, or patches of thick hair, on the chelipeds and legs. They can range from green to brown in coloration. Adult crabs are generally 2–4 cm (0.8–1.6 in) wide at the carapace, although the smallest mature crabs can be around just 1 cm (0.4 in) wide. and are able to survive and reproduce in environments of widely varying salinities.
The Bythograeidae are a small family of blind crabs which live around hydrothermal vents. The family contains 16 species in six genera. Their relationships to other crabs are unclear. They are believed to eat bacteria and other vent organisms. Bythograeidae are a monophyletic, sister taxon of the superfamily Xanthoidea which split to inhabit hydrothermal vents around the Eocene.
Discoplax is a genus of terrestrial crabs. It is very closely related to the genus Cardisoma.
Gandalfus yunohana is a species of blind crab in the family Bythograeidae found on hydrothermal vents on the eastern edge of the Philippine Sea Plate south of Japan. Because no light penetrates to such depths, the eyes of G. yunohana are immobile and unpigmented.
Euryxanthops is a genus of crabs in the family Xanthidae. It was originally established in 1983 by Garth & Kim to contain three species of deep-water crabs from Japan and the Philippines - Euryxanthops dorsiconvexus, Euryxanthops flexidentatus and Euryxanthops orientalis. Since then, several more species of this genus have been identified and described, and Euryxanthops currently contains:
Cyanagraea praedator is a species of crab that lives on hydrothermal vents, and the only species in the genus Cyanagraea.
The Panopeidae are a family containing 26 genera of morphologically similar crabs, often known as "mud crabs". Their centers of diversity are the Atlantic Ocean and eastern Pacific Ocean.
Euryxanthops chiltoni is a species of crab found in the New Zealand Exclusive Economic Zone. It was first described by Colin McLay and Peter Ng in a 2007 paper, along with Medaeops serenei.
Gandalfus puia is the only known New Zealand species of crab in the family Bythograeidae, commonly known as the blind vent crabs. Like other blind vent crabs, it only lives in hydrothermal vent waters. This species was first described in 2007 after specimens were collected from the undersea volcanic ridge near the Kermadec Islands.
Arquatopotamon jizushanense is a freshwater crab species found in Yunnan, China, and the only species of the genus Arquatopotamon. Its carapace is normally darkish brown and the walking legs and chelipeds more reddish brown.
Nanhaipotamon is a genus of freshwater crabs, in the subfamily Potamiscinae, found in southern China and Taiwan. As of 2018, 18 species have been described. The genus is named after the South China Sea, for it occurs mostly in coastal areas. The genus was first described by R. Bott in 1968 as Isolapotamon (Nanhaipotamon), i.e., a subgenus of Isolapotamon.
Gandalfus is a genus of crabs belonging to the family Bythograeidae. Gandalfus species occur around hydrothermal vents.
Parveen F. Absar is a wildlife biologist from India. In 2017, she was credited with the discovery of a species of freshwater crab called Teretamon absarum, of the genus Teretamon and species speleaum.
Alain raymondi is a species of crab in the Pinnotheridae family. It was first described in 2008 by Ahyong and Peter Ng. The species epithet, raymondi, honours Ray Manning.
Microthelphusa wymani is a species from the genus Microthelphusa.
