Anomura

Anomura Temporal range: Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N
The hermit crab Dardanus megistos
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Decapoda
Suborder:	Pleocyemata
(unranked):	Reptantia
Infraorder:	Anomura Macleay, 1838
Superfamilies
Aegloidea Chirostyloidea † Eocarcinoidea Galatheoidea Hippoidea Lithodoidea Lomisoidea Paguroidea

Anomura (sometimes Anomala) is a group of

The name Anomura derives from an old classification in which reptant decapods were divided into Macrura (long-tailed), Brachyura (short-tailed) and Anomura (differently-tailed). The alternative name Anomala reflects the unusual variety of forms in this group; whereas all crabs share some obvious similarities, the various groups of anomurans are quite dissimilar.^[3]

The group has been moulded by several instances of carcinisation – the development of a crab-like body form.^[4] Thus, the king crabs (Lithodidae), porcelain crabs (Porcellanidae) and hairy stone crab (Lomisidae) are all separate instances of carcinisation.^[4]

As decapods (meaning ten-legged), anomurans have ten

The cladogram below shows Anomura's placement within the larger order Decapoda, from analysis by Wolfe et al. (2019).^[7]

Decapoda

Dendrobranchiata (prawns)  Pleocyemata   Stenopodidea (boxer shrimp)  Procarididea  Caridea (true shrimp)  Reptantia   Achelata (spiny lobsters, slipper lobsters)  Polychelida (benthic crustaceans)  Astacidea (lobsters, crayfish)        Axiidea (mud shrimp, ghost shrimp, or burrowing shrimp)  Gebiidea (mud lobsters and mud shrimp)  Meiura   Anomura (hermit crabs and others)   Brachyura (crabs)  (crawling / walking decapods)

Some of the internal relationships within Anomura can be shown in the cladogram below, which shows Hippidae as

The infraorder Anomura contained seven extant superfamilies:[8]^[9][10][11]

Superfamily	Members	Families	Photo
Aegloidea	Aegla	Aeglidae	Aegla sp.
Chirostyloidea	squat lobsters	Kiwaidae	Eumunida picta
† Eocarcinoidea	† Eocarcinus † Platykotta	† Eocarcinidae † Platykottidae
Galatheoidea	squat lobsters porcelain crabs	Galatheidae Munididae Munidopsidae Porcellanidae † Retrorsichelidae	Munidopsis serricornis (Munidopsidae)
Hippoidea	mole crabs or sand crabs	Albuneidae Blepharipodidae Hippidae	Blepharipoda occidentalis (Blepharipodidae)
Lithodoidea	king crabs	Lithodidae	Lithodes santolla (Lithodidae)
Lomisoidea	hairy stone crab	Lomisidae	Lomis hirta (Lomisidae)
Paguroidea	hermit crabs coconut crab	Coenobitidae Diogenidae Paguridae Parapaguridae Parapylochelidae Pylochelidae Pylojacquesidae	Coenobita clypeatus (Coenobitidae )

The oldest fossil attributed to Anomura is Platykotta, from the Norian–Rhaetian (Late Triassic) Period in the United Arab Emirates.^[9]

References