Eurypterina

Eurypterina Temporal range: Middle Ordovician - Early Permian, 467.3–283.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N
The defining characteristic of eurypterine eurypterids is the transformation of the sixth pair of legs into swimming paddles. Reconstructed leg of Bassipterus.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Clade:	Sclerophorata
Order:	†Eurypterida
Suborder:	†Eurypterina Burmeister, 1843
Type species
†Eurypterus remipes De Kay, 1825
Subgroups
†Onychopterelloidea †Moselopteroidea †Eurypteroidea †Diploperculata †Carcinosomatoidea †Waeringopteroidea †Adelophthalmoidea †Pterygotioidea Incertae sedis †Wiedopterus
Synonyms
Pterygotina Caster & Kjellesvig-Waering, 1964

Eurypterina is one of two suborders of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". Eurypterine eurypterids are sometimes informally known as "swimming eurypterids".^[1] They are known from fossil deposits worldwide, though primarily in North America and Europe.

Seventy-five percent of eurypterid species are eurypterines; this represents 99% of specimens.^[2] The superfamily Pterygotioidea is the most species-rich clade, with 56 species, followed by the Adelophthalmoidea with 43 species; as sister taxa, they comprise the most derived eurypterines. Pterygotioidea includes the pterygotids, which are the only eurypterids known to have a cosmopolitan distribution.^[3]

Though more numerous both in specimens and taxa, the eurypterines have the shorter temporal range of the two eurypterid suborders. They first appeared around the same time as the Stylonurina in the Middle Ordovician. The suborder faced a slow extinction during the Middle and Late Devonian, possibly tied to the emergence of jawed vertebrates.^[4] Every Eurypterine genus and lineage went extinct before the Carboniferous save for Adelophthalmus which would go extinct in the Early Permian, millions of years before the Permian-Triassic extinction event that ended the stylonurines.^[5]