The suborder faced a slow extinction during the Middle and Late Devonian, possibly tied to the emergence of jawed vertebrates.

In the Stylonurina, this appendage takes the form of a long and slender walking leg, lacking a modified spine (termed podomere 7a).

[3] The most basal eurypterines with swimming legs, the genus Onychopterella, are known from the east coast of Gondwana close to the equator (a region that today is South Africa) from the Late Ordovician.

Isolated and fragmentary fossils from the Late Silurian of Vietnam and the Czech Republic show that the terranes of Annamia and Perunica were within the geographical range of the carcinosomatoids.

Only a few basal carcinosomatoids (e.g. Carcinosoma and Paracarcinosoma) have been found in deeper waters whilst the more derived forms, such as Mixopterus and Lanarkopterus have not.

Fossil remains have been recovered from Australia, Libya, Algeria, Morocco, Florida, Saudi Arabia, Iberia, South America, vast swaths of Gondwana, Bohemia and Siberia.

The Carcinosomatoidea have a poorly resolved internal phylogeny, though can be easily recognised by scorpion-like appearance and heavily spinose appendages.

Eurypterines are characterised by the transformation of the posteriormost prosomal appendage into a swimming paddle, one of the main features used to distinguish them from the stylonurines.

The cladogram presented below, simplified from a study by Tetlie,[3] showcases the phylogenetic relationships of the Eurypterina based on this adaptation, and the enlargement of the chelicerae, which characterises the family Pterygotidae, to be used for active prey capture.Stylonurina Megalograptoidea Eurypteroidea Carcinosomatoidea Waeringopteroidea Adelophthalmoidea Hughmilleria Herefordopterus Slimonia Pterygotidae