Құрышқан шаяндар туысы Eurypterus

Extinct genus of sea scorpions

Eurypterus (/j//ʊəˈr//ɪ//p//t//ər//ə//s/ yooRIPtərəs) is an extinct genus of eurypterid, a group of organisms commonly called "sea scorpions". The genus lived during the Silurian period, from around 432 to 418 million years ago. Eurypterus is by far the most well studied and well known eurypterid. Eurypterus fossil specimens probably represent more than 95% of all known eurypterid specimens. There are fifteen species belonging to the genus Eurypterus, the most common of which is E. remipes, the first eurypterid fossil discovered and the state fossil of New York. Members of Eurypterus averaged at about in length, but the largest individual discovered was estimated to be long. They all possessed spine bearing appendages and a large paddle they used for swimming. They were generalist species, equally likely to engage in predation or scavenging.

The first fossil of Eurypterus was found in 1818 by S. L. Mitchill, a fossil collector. It was recovered from the Bertie Formation of New York (near Westmoreland, Oneida County). Mitchill interpreted the appendages on the carapace as barbels arising from the mouth. It was only after seven years, in 1825, that the American zoologist James Ellsworth De Kay identified the fossil correctly as an arthropod. He named it Eurypterus remipes and established the genus Eurypterus in the process. The name means 'wide wing' or 'broad paddle', referring to the swimming legs, from Greek εὐρύς (eurús 'wide') and πτερόν (pteron 'wing').

The largest arthropods to have ever existed were eurypterids. The largest known species (Jaekelopterus rhenaniae) reached up to in length, about the size of a crocodile. Species of Eurypterus, however, were much smaller. E. remipes are usually between in length. E. lacustris average at larger sizes at in length. However, a single telson (the posteriormost division of the body) of a specimen of this species reaches this length, being long and indicating a specimen of of length, and that is the largest specimen ever described in literature. In the introduction page of E. remipes in website of University of Texas at Austin says that the largest specimen ever found was long, currently on display at the Paleontological Research Institution of New York. However, the text section describes the group eurypterid itself rather than Eurypterus, so it is not possible to determine in context whether the long specimen is actually from E. remipes or another eurypterid. Eurypterus fossils often occur in similar sizes in a given area. This may be a result of the fossils being "sorted" into windrows as they were being deposited in shallow waters by storms and wave action. The Eurypterus body is broadly divided into two parts: the prosoma and the opisthosoma (in turn divided into the mesosoma and the metasoma). The prosoma is the forward part of the body, it is actually composed of six segments fused together to form the head and the thorax. They also possessed two smaller light sensitive simple eyes (the median ocelli) near the center of the carapace on a small elevation (known as the ocellar mound). Underneath the carapace is the mouth and six appendages, usually referred to in Roman numerals I VI. Each appendage in turn is composed of nine segments (known as podomeres) labeled in Arabic numerals 1–9. The first segments which connect the appendages to the body are known as the coxa (plural coxae). It is further subdivided in two ways. Based on the width and structure of each segment, they can be divided into the broad preabdomen (segments 1 to 7) and the narrow postabdomen (segments 8 to 12). The preabdomen is the broader segments of the anterior portion of the ophisthosoma while the postabdomen are the last five segments of the Eurypterus body. Each of the segments of the postabdomen contain lateral flattened protrusions known as the epimera with the exception of the last needle like (styliform) part of the body known as the telson. The segment immediately preceding the telson (which also has the largest epimera of the postabdomen) is known as the pretelson. The mesosoma contains the gills and reproductive organs of Eurypterus. Its ventral segments are overlaid by appendage derived plates known as Blattfüsse (singular Blattfuss, German for "sheet foot"). Protected within which are the branchial chambers which contain the respiratory organs of Eurypterus. Eurypterus are sexually dimorphic. On the bottom side of the first two segments of the mesosoma are central appendages used for reproduction. In females, they are long and narrow. In the males they are very short.