Eurypteridae are an extinct family of eurypterids. They were members of the superfamily Eurypteroidea

Eurypteroidea

Eurypteroidea are an extinct superfamily of eurypterids.-Description:Eurypteroidea, which lived from the Ordovician to Permian periods, were characterized by their last pair of prosomal appendages, which were developed as swimming legs, carrying paddles formed by the expansion of the two...

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Description

Eurypteridae, which lived during the Silurian

Silurian

The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...

 period, were characterized by small to large exoskeletons with inconspicuous semilunar scales or curved ridges. The telson

Telson

The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...

, (tail) was styliform, or pointed. Eurypteridae also had chelicerae (appendages in front of the mouth) that were small. Their walking legs were covered in spines. The prosoma (head) was subrectangular, with slightly curved compound eyes located relatively centrally on the dorsal surface. Genital appendages in the female were very short with lateral lobes in the female, but long in the nale, with diverging distal spines.

Genera

• Class Merostomata
  Merostomata
  Merostomata is the name given to a grouping of the extinct Eurypterida and the Xiphosura . The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups....
  
   Dana, 1852
• Order Eurypterida Burmeister, 1843
• Suborder Eurypterina Burmeister, 1843
• Superfamily Eurypteroidea
  Eurypteroidea
  Eurypteroidea are an extinct superfamily of eurypterids.-Description:Eurypteroidea, which lived from the Ordovician to Permian periods, were characterized by their last pair of prosomal appendages, which were developed as swimming legs, carrying paddles formed by the expansion of the two...
  
   Burmeister, 1843

  Family Eurypteridae Burmeister, 1843

  Genus Eurypterus

  Eurypterus

  Eurypterus is an extinct genus of sea scorpions. They existed during the Silurian Period, from around 432 to 418 million years ago.There are fifteen species belonging to the genus Eurypterus, the most common of which is Eurypterus remipes, the first eurypterid fossil discovered and the state...

  
  De Kay, 1825