Hemigrapsus is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of varunid

Varunidae

Varunidae is a family of thoracotrematan crabs. The delimitation of this family, part of the taxonomically confusing Grapsoidea, is undergoing revision. For a long time, they were placed at the rank of subfamily in the Grapsidae, but they appear to be closest to Macropthalmus and the Mictyridae,...

 crab

Crab

True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

s.

The genus is restricted to the Pacific Ocean, except for Hemigrapsus affinis which lives along the Atlantic coasts of South America, from Cape San Roque (Rio Grande do Norte

Rio Grande do Norte

Rio Grande do Norte is one of the states of Brazil, located in the northeastern region of the country, occupying the northeasternmost tip of the South American continent. Because of its geographic position, Rio Grande do Norte has a strategic importance. The capital and largest city is Natal...

 state, Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

) to the Gulf of San Matias, (Patagonia

Patagonia

Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...

, Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

), and a population of Hemigrapsus sanguineus which has been introduced to New Jersey

New Jersey

New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

 from its native range in East Asia

East Asia

East Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms...

, and now ranges from Portland, Maine

Portland, Maine

Portland is the largest city in Maine and is the county seat of Cumberland County. The 2010 city population was 66,194, growing 3 percent since the census of 2000...

 to North Carolina

North Carolina

North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...

. H. estellinensis

Hemigrapsus estellinensis

Hemigrapsus estellinensis is a extinct species of crab, formerly endemic to the Texas Panhandle. It was discovered by Gordon C. Creel in 1962 and was probably already extinct before his description was published in 1964, after the Estelline Salt Springs where it lived were contained by the United...

is almost certainly extinct

Extinction

In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

, but was endemic to a hypersaline spring in the Texas Panhandle

Texas Panhandle

The Texas Panhandle is a region of the U.S. state of Texas consisting of the northernmost 26 counties in the state. The panhandle is a rectangular area bordered by New Mexico to the west and Oklahoma to the north and east...

, 500 miles (804.7 km) from the sea.

Thirteen species are currently recognised:

• Hemigrapsus affinis Dana, 1851
• Hemigrapsus crassimanus Dana, 1851
• Hemigrapsus crenulatus (H. Milne-Edwards, 1837)
• Hemigrapsus estellinensis
  Hemigrapsus estellinensis
  Hemigrapsus estellinensis is a extinct species of crab, formerly endemic to the Texas Panhandle. It was discovered by Gordon C. Creel in 1962 and was probably already extinct before his description was published in 1964, after the Estelline Salt Springs where it lived were contained by the United...
  
  Creel, 1964
• Hemigrapsus gibbus (Hombron & Jacquinot, 1846)
• Hemigrapsus longitarsus (Miers, 1879)
• Hemigrapsus nudus (Dana, 1851)
• Hemigrapsus octodentatus (H. Milne-Edwards, 1837)
• Hemigrapsus oregonensis (Dana, 1851)
• Hemigrapsus pallipes (H. Milne-Edwards, 1837)
• Hemigrapsus penicillatus (De Haan, 1835)
• Hemigrapsus sanguineus (De Haan, 1835)
• Hemigrapsus sexdentatus (H. Milne-Edwards, 1837)
• Hemigrapsus sinensis Rathbun, 1931
• Hemigrapsus takanoi Asakura & Watanabe, 2005