Euthycarcinoidea

The euthycarcinoid body was divided into a cephalon (head), preabdomen, and postabdomen. The cephalon consisted of two segments and included mandibles, antennae and presumed eyes. The preabdomen consisted of five to fourteen tergites, each having up to three somites. Each somite had in turn a pair of uniramous, segmented legs. The postabdomen was limbless and consisted of up to six segments and a terminal tail spine. macnaughtoni'' from the Elk Mound Group, Blackberry Hill, central Wisconsin. Cambrian euthycarcinoids such as this one may have been the first animals to walk and survive on land. ==Affinities==

Due to its particular combination of characteristics, the position of the Euthycarcinoidea within the Arthropoda has been ambiguous; previous authors have allied euthycarcinoids with crustaceans (interpreted as copepods, branchiopods, or an independent group), with trilobites, or the merostomatans (horseshoe crabs and sea scorpions, now an obsolete group }} }} }}}}}} }}}} }}}}}}}}}}}}}}}}}}}}}}}}|label1=Mandibulata}} ==Environment and life habits==

Euthycarcinoid fossils have been found in marine, brackish and freshwater deposits. Taxa from the Cambrian are from marine or intertidal sediments, while all specimens from the Ordovician to the Triassic are freshwater or brackish. Fossil impressions of euthycarcinoid postabdomens in association with Protichnites trackways in Cambrian intertidal/supratidal deposits also suggest that euthycarcinoids may have been the first arthropods to walk on land. It has been suggested that the biofilms and microbial mats that covered much of the vast tidal flats during the Cambrian Period in North America may have provided the nourishment that lured these arthropods onto the land. Fossil evidence also suggests the possibility that some euthycarcinoids came onto the land to lay and fertilize their eggs via amplexus, as do the modern horseshoe crabs. ==Classification==

The known species of euthycarcinoids and their distribution were reviewed by Racheboeuf et al. in 2008. Additional species were described by Collette and Hagadorn in 2010. ==References==