Reptantia is a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

of decapod

crustacean 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 group ...

s named in 1880 which includes

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 ...

crab 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 ...

s and many other well-known crustaceans.

Classification

In older classifications, Reptantia was one of the two sub-orders of

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 ...

alongside

Natantia Natantia (Boas, 1880) is an obsolete taxon of decapod crustaceans, comprising those families that move predominantly by swimming – the shrimp (comprising Caridea and Procarididea), prawns (Dendrobranchiata) and boxer shrimp. The remaining Decap ...

, with Reptantia containing the walking forms, and Natantia containing the swimming forms (

prawn Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs (which is a member of the order decapoda), some of which can be eaten. The term "prawn"Mortenson, Philip B (2010''This is not a weasel: a close look at nature ...

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

and

boxer shrimp The Stenopodidea or boxer shrimps are a small group of decapod crustaceans. Often confused with Caridea shrimp or Dendrobranchiata prawns, they are neither, belonging to their own group. Anatomy They can be differentiated from the Dendrobranc ...

). However, in 1963

Martin Burkenroad Martin David Burkenroad (March 20, 1910 – January 12, 1986) was an American marine biologist. He specialized in decapod crustaceans and fisheries science. Biography Burkenroad was born in New Orleans in 1910 as the only child of coffee import ...

found

to be

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

and invalid, and instead split Decapoda into the two sub-orders of

Dendrobranchiata Dendrobranchiata is a suborder of Decapoda, decapods, commonly known as prawns. There are 540 extant species in seven families, and a fossil record extending back to the Devonian. They differ from related animals, such as Caridea and Stenopodidea ...

(prawns) and

Pleocyemata Pleocyemata is a suborder of decapod crustaceans, erected by Martin Burkenroad in 1963. Burkenroad's classification replaced the earlier sub-orders of Natantia and Reptantia with the monophyletic groups Dendrobranchiata (prawns) and Pleocyemata. ...

. Pleocyemata contains all the members of the Reptantia (including crabs, lobsters, crayfish, and others), as well as the

Stenopodidea The Stenopodidea or boxer shrimps are a small group of decapod crustaceans. Often confused with Caridea shrimp or Dendrobranchiata prawns, they are neither, belonging to their own group. Anatomy They can be differentiated from the Dendrobranc ...

("boxer shrimp"), and

Caridea The Caridea, commonly known as caridean shrimp or true shrimp, are an infraorder of shrimp within the order Decapoda. This infraorder contains all species of true shrimp. They are found widely around the world in both fresh and salt water. Many ...

(true shrimp). Reptantia remains a valid

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

grouping, but is now no longer ranked as a sub-order.

Anatomy

The name Reptantia means "those that walk", and contains those decapods whose primary mode of locomotion is to walk along a surface using the pereiopods rather than swimming through the water with the

pleopods The decapod ( crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in variou ...

. Despite this, many reptants are able to propel themselves through the water, and many non-reptants can and will walk.

Systematics

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 Reptantia under the sub-order

within the larger order

, from analysis by Wolfe ''et al.'', 2019. Reptantia comprises the following

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 ...

s: *

Achelata The Achelata is an infra-order of the decapod crustaceans, holding the spiny lobsters, slipper lobsters and their fossil relatives. Description The name "Achelata" derives from the fact that all the members of this group lack the chelae (claw ...

(spiny, slipper, and furry lobsters) *

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 ...

(benthic crustaceans) *

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 ...

(glypheoid lobsters) *

Astacidea Astacidea is an infraorder of decapod crustaceans including lobsters (though not "lobsters" such as the spiny lobster etc.), crayfish, and their close relatives. Description The Astacidea are distinguished from most other decapods by the presen ...

(true lobsters, reef lobsters, and crayfish) *

Axiidea Axiidea is an infraorder of decapod crustaceans. They are colloquially known as mud shrimp, ghost shrimp, or burrowing shrimp; however, these decapods are only distantly related to true shrimp. Axiidea and Gebiidea are divergent infraoders of ...

(mud lobsters and ghost shrimp) *

Gebiidea Gebiidea is an infraorder of Decapoda, decapod crustaceans. Gebiidea and Axiidea are divergent infraoders of the former infraorder Thalassinidea. These infraorders have converged Ecology, ecologically and Morphology (biology), morphologically as ...

(mud lobsters and mud shrimp) *

Anomura Anomura (sometimes Anomala) is a group of Decapoda, decapod crustaceans, including hermit crabs and others. Although the names of many anomurans include the word ''crab'', all true crabs are in the sister group to the Anomura, the Brachyura (the ...

(squat lobsters, hermit crabs, and relatives) * Brachyura (true crabs)

References

{{Decapoda Decapods Extant Devonian first appearances Unranked clades