Eurypterid

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iEurypterids

Eurypterid from Ernst Haeckel's Kunstformen der Natur, 1904.

Extinct (fossil)

Scientific classification

Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Class:	Eurypterida

Orders

†Stylonuroidea Diener, 1924
†Eurypteroidea Burmeister, 1843

The eurypterids were the largest known arthropods that ever lived (with the possible exception of Anomalocarids). They are members of the extinct class Eurypterida (Arachnomorpha, Chelicerata) and predate the earliest fishes. The largest, such as Pterygotus, reached 2 m or more in length, but most species were less than 20 cm. They were formidable predators that thrived in warm shallow water in the Cambrian to Permian from 510 to 248 million years ago. Eurypterids were the most fearsome swimming predators of the Palaeozoic. Although called "sea scorpions", only the earliest ones were marine (most lived in brackish or freshwater), and they were not true scorpions. The move from the sea to fresh water probably occurred by the Pennsylvanian period.

Eurypterus is perhaps the most well-known genus of eurypterid, of which 200 fossil species are known. The genus Eurypterus was created in 1825 by James Ellsworth DeKay, a zoologist. He recognized the arthropod nature of the first ever described eurypterid specimen found by Dr. S. L. Mitchell. In 1984, Eurypterus remipes was named the State Fossil of New York.

1 Body structure
2 Eurypterid fossils
3 Classification by Tollerton, 1989
4 See also
5 References

[edit] Body structure

The typical eurypterid had a large, flat, semicircular carapace, followed by a jointed section, and finally a tapering, flexible tail, with a long spine at the end. Behind the head of the eurypterids were twelve body segments. These segments are formed by a dorsal plate called tergite, and a ventral plate called sternite. The tail, which is spiked, and in some species may have been used to inject venom, like in modern scorpions, is known as the telson. Some eurypterids have paddles, which were used to propel themselves through water. Some argue that the paddles were also used for digging. Underneath, in addition to the pair of swimming appendages the creature had 4 pairs of jointed legs for walking, and two small claws at the front, chelicerae. Other features, common to ancient and modern arthropods of this type, include one pair of compound eyes and a pair of smaller eyes called ocelli.

Although many eurypterids had legs too tiny to do more than allow them to crawl over the sea bottom, a number of forms had large stout legs, and were clearly capable of terrestrial locomotion (like land crabs today). While functional studies suggest that eurypterids used out-of-phase walking techniques, their trackways indicate that they used in-phase, hexapodous (six-legged) and octopodous (eight-legged) gaits. Some species may have been amphibious, emerging onto land for at least part of their life cycle. They may have been capable of breathing both in water and in air.

[edit] Eurypterid fossils

Eurypterid fossils have been found on nearly every continent. Locations currently producing excellent fossils include western New York State and southern Ontario, Canada, in Silurian rocks. Although relatively rare, the fossils are famous for excellent preservation. Eurypterid fossils are routinely found at Ridgemount Quarry, in Fort Erie, Ontario Canada. A commercial eurypterid quarry has been open for several years in Mohawk, New York.

Among the largest eurypterids are the Hibbertopterina, named after the British palaeontolgist S. Hibbert, who described Hibbertopterus scouleri at a limestone quarry in East Kirkton, Scotland, in 1836. Fossil tracks (a form of trace fossil) were identified recently in East Lothian, Scotland, as made by a 1.6-meter-long Hibbertopterus (Whyte, 2005).

Eurypterids are related to the modern marine horseshoe crabs and land scorpions. About two dozen families of eurypterids are known. They went extinct in the Permian-Triassic extinction event 248 million years ago (m.y.a.).

[edit] Classification by Tollerton, 1989

There are more than 300 identified species of the extinct sea scorpions. They have been classified by Tollerton (1989) and others in more than 60 genera and in about 20 families:

Glyptoscorpioidae

Glyptoscorpiidae
- Glyptoscorpius
  - G. perornatus
Belinuropsidae
- Belinuropsis
  - B. wigodensis

Slimonioidea

Slimoniidae
- Slimonia
  - S. acuminatus
- Himantopterus
  - H. acuminata

Hughmillerioidea

Hughmilleriidae
- Hastimima
  - H. whitei
- Hughmilleria
  - H. socialis
  - H. norvegica
  - H. bellistriata
- Salteropterus
  - S. abbreviatus
- Grossopterus
  - G. overathi
- Lepidoderma
  - L. mansfieldi
  - L. mazonense

Carcinosomatidae
- Carcinosoma
  - C. newlini
  - C. vaningeni
  - C. scorpionis
Adelophthalmidae
- Adelophthalmus
  - A. imhofi
- Lepidoderma
  - L. imhofi

Mixopteroidea

Mixopteridae
- Mixopterus
  - M. multispinosus
  - M. kiaeri
Lanarkopteridae

Megalograptoidea

Megalograptidae
- Megalograptus
  - M. welchi
  - M. ohioensis
- Echinognathus
  - E. clevelandi

Eurypteroidea

Eurypteridae
- Eurypterus
  - E. clevelandi
  - E. cestrotus
  - E. remipes
  - E. fischeri
  - E. kokomoensis
  - E. boyli
  - E. ? abbreviatus
  - E.? overathi
- Onychopterella
  - O. kokomoensis
- Tylopterella
  - T. boyli

Dolichopteridae
- Dolichopterus
  - D. macrocheirus
- Strobilopterus
  - S. princetoni
Erieopteridae

Stylonuroidea

Stylonuridae
- Stylonurus
  - S. powriei
  - S. dolichopteroides
  - S. logani
  - S. macrophthalmus
  - S. scoticus
  - S.? multispinosus
- Drepanopterus
  - D. pentlandicus
  - D. longicaudatus
- Brachyopterus
  - B. stubblefieldi
  - B. pentagonalis
- Ctenopterus
  - C. cestrotus
- Tarsopterella
  - T. scoticus
- Melbournopterus
  - M. crossotus
- Campulocephalus
  - C. oculatus
  - C. scouleri

Dolichocephala

Claypolidae (?)
- Claypole
  - C.? lacoana
Drepanopteridae
Parastylonuridae
Laurieipteridae

Kokomopteroidea

Kokomopteridae
Hardieopteridae

Brachyopterelloidea

Brachyopterellidae

Rhenopteroidea

Rhenopteridae
- Rhenopterus
  - R. diensti

Mycopteropoidea

Mycteropidae
- Mycterops
  - M. scabrosus
  - M. mathieui
Woodwardopteridae
- Woodwardopterus

Pterygotoidea

Jaekelopteridae
Pterygotidae
- Pterygotus
  - P. (P.) rhenaniae
  - P. (P.) anglicus
  - P. (A.) buffaloensis
  - P. (A.) bohemicus
  - P. (P.) osiliensis
  - P. (P.) bilobus
- Acutiramus
- Erettopterus
- Himantopterus

Incertae sedis (phylogeneticly troublesome)

Willwerathia
Tylopterella
Tarsopterella
Pittsfordipterus
Dorfopterus
Melbournopterus
Hallipterus
Megarachne
Palmichnium
Waeringoopterus

[edit] See also

Hibbertopteroid track

[edit] References

Ciurca, Samuel J. (1998). The Silurian Eurypterid Fauna (http://www.eurypterid.net/ ). Retrieved July 25, 2004.
Clarke, John M. & Rudolf R. The Eurypterida of New York. Albany: New York State Education Department, 1912.
Whyte, Martin A. "Palaeoecology: A gigantic fossil arthropod trackway". Nature 438, 576-576 (01 December 2005).

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Category: Prehistoric arthropods