What is Cephalocarida?
{{Taxobox | name = Cephalocarida | image = File:Hutchinsoniella macracantha (YPM IZ 003617.CR) 001.jpeg | image_caption = ''[[Hutchinsoniella macracantha]]'' | regnum = [[Animal]]ia | phylum = [[Arthropod]]a | subphylum = [[Crustacean|Crustacea]] | classis = '''Cephalocarida''' | ordo = '''Brachypoda''' | familia = '''Hutchinsoniellidae''' | familia_authority = [[Howard L. Sanders|Sanders]], 1955 | subdivision_ranks = [[Genus|Genera]] | subdivision = *''[[Chiltoniella]]'' *''[[Hampsonellus]]'' *''[[Hutchinsoniella]]'' *''[[Lightiella]]'' *''[[Sandersiella]]'' | synonyms = * Lightiellidae <small>Jones 1961</small> }} '''Cephalocarida''' is a [[class (biology)|class]] inside the sub[[phylum]] [[Crustacean|Crustacea]] that has only twelve [[shrimp]]-like benthic [[species]]. They were discovered in 1955, and are commonly referred to as '''horseshoe shrimps'''. All cephalocaridans are in just one family: '''Hutchinsoniellidae'''. Even though there is no [[fossil]] record of cephalocaridans, most specialists believe them to be [[basal]] (primitive) among crustaceans. == Description and anatomy == These crustaceans are from {{convert|2|to|4|mm}} in length, with a long body. They have no eyes, and live in a [[mud]]dy natural [[habitat]].<ref name=IZ>{{cite book |author= Barnes, Robert D. |year=1982 |title= Invertebrate Zoology |publisher= Holt-Saunders International |location= Philadelphia, PA|page= 672|isbn= 0-03-056747-5}}</ref> The structural and functional similarity between the maxillae and the legs may be a sign of primitive organization; the maxillae are not specialized, as they are in other crustaceans.<ref name=IZ /> The [[thorax]] consists of 10 segments, and the abdomen bears a [[telson]] but no other appendages. == Ecology == Cephalocaridans are found from the [[intertidal zone]] down to a depth of 1500 metres, in all kinds of [[sediment]]s. They feed on marine [[detritus]]. To bring in food particles, they make water currents with the thoracic appendages like the [[branchiopod]]s and the [[malacostra