Astacidea is an
infraorder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
of
decapod crustacea
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...
ns including
lobster
Lobsters are a family (biology), family (Nephropidae, Synonym (taxonomy), synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs ...
s (though not "lobsters" such as the
spiny lobster
Spiny lobsters, also known as langustas, langouste, or rock lobsters, are a family (Palinuridae) of about 60 species of achelate crustaceans, in the Decapoda Reptantia. Spiny lobsters are also, especially in Australia, New Zealand, Ireland, So ...
etc.),
crayfish
Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...
, and their close relatives.
Description
The Astacidea are distinguished from most other decapods by the presence of
chelae
A chela ()also called a claw, nipper, or pinceris a pincer (biology), pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are ...
(claws) on each of the first three pairs of
pereiopods (walking legs), the first of which is much larger than the remaining two pairs.
The last two pairs of pereiopods are simple (without claws), except in ''
Thaumastocheles
The family Thaumastochelidae contains five known species of deep-sea lobsters, three in the genus ''Thaumastocheles'', and two in the genus ''Thaumastochelopsis''. The fifth species was discovered in the ten–year Census of Marine Life. These cr ...
'', where the fifth pereiopod may have "a minute pincer".
Distribution
Members of the infraorder Astacidea are found throughout the world – both in the
ocean
The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
s and in
fresh water
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
– except for mainland Africa and parts of Asia.
Classification
Astacidea belongs to the group
Reptantia
Reptantia is a clade of decapod crustaceans named in 1880 which includes lobsters, crabs and many other well-known crustaceans.
Classification
In older classifications, Reptantia was one of the two sub-orders of Decapoda alongside Natantia, w ...
, which consists of the walking/crawling decapods (lobsters and
crabs
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...
).
Astacidea is the
sister clade
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and t ...
to the infraorder
Polychelida
Polychelida is an infraorder of decapod crustaceans. Fossil representatives are known dating from as far back as the Upper Triassic. A total of 38 extant species, all in the family Polychelidae, and 55 fossil species have been described.
Histor ...
, a small group of crustaceans restricted to deep waters. The
cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
below shows Astacidea's placement within the larger
order Decapoda
The Decapoda or decapods (literally "ten-footed") are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crabs, lobsters, crayfish, shrimp and prawns. Most decapods are scavengers. The order is esti ...
, from analysis by Wolfe ''et al.'', 2019.
The infraorder Astacidea comprises five extant superfamilies, two of
crayfish
Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...
(
Astacoidea
Astacoidea is superfamily of freshwater crayfish that live in the Northern Hemisphere. The other superfamily of crayfish, Parastacoidea, lives in the Southern Hemisphere. Astacoidea consists of three families: Astacidae (from Europe and weste ...
and
Parastacoidea
The Parastacidae are the family of freshwater crayfish found in the Southern Hemisphere. The family is a classic Gondwana-distributed taxon, with extant members in South America, Madagascar, Australia, New Zealand, and New Guinea, and extinct ta ...
), one of true
lobster
Lobsters are a family (biology), family (Nephropidae, Synonym (taxonomy), synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs ...
s (Nephropoidea), one of
reef lobster
Reef lobsters, ''Enoplometopus'', are a genus of small lobsters that live on reefs in the Indo-Pacific, Caribbean and warmer parts of the Atlantic Ocean.
Description
Species of ''Enoplometopus'' occur from coral reefs at depths of less than to ...
s (the genus ''
Enoplometopus''), and a number of fossil taxa.
, the group contains 782 recognised species, over 400 of which are in the crayfish family
Cambaridae
The Cambaridae are the largest of the four families of freshwater crayfish, with over 400 Species. Most of the species in the family are native the United States east of the Great Divide and Mexico, but fewer range north to Canada, and south to ...
.
The members of the infraorder
Glypheidea
Glypheidea is an infraorder of lobster-like Decapoda, decapod crustaceans, comprising a number of fossil forms and the two extant taxon, extant (living) genera ''Neoglyphea'' and ''Laurentaeglyphea'': The infraorder was thought to be extinct unti ...
(containing numerous fossils and the two extant species ''
Neoglyphea inopinata
''Neoglyphea inopinata'' is a species of glypheoid lobster, a group thought long extinct before ''Neoglyphea'' was discovered. It is a lobster-like animal, up to around in length, although without claws. It is only known from 17 specimens, ca ...
'' and ''
Laurentaeglyphea neocaledonica'') were formerly included here.
The
cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
below shows Astacidea's internal relationships and the early split between
lobsters
Lobsters are a family (Nephropidae, synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs have claws, including the first pair, ...
and
crayfish
Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...
:
Taxonomy
*
Palaeopalaemon
''Palaeopalaemon'' is an extinct genus of the oldest lobster-like aquatic decapod crustaceans, containing the species ''Palaeopalaemon newberryi''.
References
{{Taxonbar, from1=Q98077933, from2=Q107155530
Decapods
Prehistoric crustacean ge ...
oidea †
*#
Palaeopalaemon
''Palaeopalaemon'' is an extinct genus of the oldest lobster-like aquatic decapod crustaceans, containing the species ''Palaeopalaemon newberryi''.
References
{{Taxonbar, from1=Q98077933, from2=Q107155530
Decapods
Prehistoric crustacean ge ...
idae †
*
Enoplometopoidea
Reef lobsters, ''Enoplometopus'', are a genus of small lobsters that live on reefs in the Indo-Pacific, Caribbean and warmer parts of the Atlantic Ocean.
Description
Species of ''Enoplometopus'' occur from coral reefs at depths of less than to ...
*#
Enoplometopidae
Reef lobsters, ''Enoplometopus'', are a genus of small lobsters that live on reefs in the Indo-Pacific, Caribbean and warmer parts of the Atlantic Ocean.
Description
Species of ''Enoplometopus'' occur from coral reefs at depths of less than ...
*#
Uncinidae †
*
Nephropoidea
Nephropoidea is a superfamily of decapod crustaceans. It contains the true lobsters in the Nephropidae (including the rare thaumastochelid lobsters), and three fossil families: Chilenophoberidae, Protastacidae and Stenochiridae. Their closes ...
*#
Chilenophoberidae †
*#
Nephropidae
Lobsters are a family (Nephropidae, synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs have claws, including the first pair, ...
*#
Protastacidae †
*#
Stenochiridae †
*
Astacoidea
Astacoidea is superfamily of freshwater crayfish that live in the Northern Hemisphere. The other superfamily of crayfish, Parastacoidea, lives in the Southern Hemisphere. Astacoidea consists of three families: Astacidae (from Europe and weste ...
[
*#]Astacidae
Astacidae is a family of freshwater crayfish native to Europe and western North America. The family is made up of four extant (living) genera: The genera ''Astacus'' (which includes the European crayfish), ''Pontastacus'' (which includes the T ...
*#Cambaridae
The Cambaridae are the largest of the four families of freshwater crayfish, with over 400 Species. Most of the species in the family are native the United States east of the Great Divide and Mexico, but fewer range north to Canada, and south to ...
*#Cambaroididae
''Cambaroides'' is a genus of freshwater crayfish from eastern Asia (eastern Russia, northeastern China, Korean Peninsula and Japan). Together with ''Astacus
''Astacus'' (from the Greek , ', meaning "lobster" or "crayfish") is a genus of c ...
*# Cricoidoscelosidae †
*Parastacoidea
The Parastacidae are the family of freshwater crayfish found in the Southern Hemisphere. The family is a classic Gondwana-distributed taxon, with extant members in South America, Madagascar, Australia, New Zealand, and New Guinea, and extinct ta ...
*#Parastacidae
The Parastacidae are the family of freshwater crayfish found in the Southern Hemisphere. The family is a classic Gondwana-distributed taxon, with extant members in South America, Madagascar, Australia, New Zealand, and New Guinea, and extinct ta ...
References
{{Authority control
Decapods
Arthropod infraorders
Taxa named by Pierre André Latreille