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 ter ...

of decapod

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

s named in 1880 which includes

lobster 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, ...

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 th ...

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 estim ...

alongside Natantia, 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 ref ...

and boxer shrimp). 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 imp ...

found Natantia to be

paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...

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

Dendrobranchiata Dendrobranchiata is a suborder of 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, by t ...

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

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

pereiopod 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 ...

s rather than swimming through the water with the pleopods. 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 ...

below shows Reptantia under the sub-order Pleocyemata within the larger

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

, 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 (spiny, slipper, and furry lobsters) * Polychelida (benthic crustaceans) * Glypheidea (glypheoid lobsters) * Astacidea (true lobsters, reef lobsters, and crayfish) * Axiidea (mud lobsters and ghost shrimp) * Gebiidea (mud lobsters and mud shrimp) * Anomura (squat lobsters, hermit crabs, and relatives) * Brachyura (true crabs)

References

{{Decapoda Decapods Extant Devonian first appearances Unranked clades