Pterygotidae

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Pterygotidae
Temporal range: LlandoveryEarly Devonian
File:Acutiramus cummingsi 02.jpg
Reconstruction of Acutiramus cummingsi
Scientific classification e
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Merostomata
Order: Eurypterida
Suborder: Eurypterina
Superfamily: Pterygotioidea
Family: Pterygotidae
Clarke & Ruedemann, 1912
Genera

See text

Synonyms

<templatestyles src="Noitalic/styles.css"/>Jaekelopteridae Størmer, 1974

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Pterygotidae are an extinct family of eurypterids. They were members of the superfamily Pterygotioidea,[1] and were the only eurypterids to have a truly worldwide distribution,[2] and include the largest arthropods to have ever lived.

Description

Pterygotidae, which lived from the late Early Silurian to the Middle Devonian,[3][4] were characterized by small to large exoskeletons with semilunar scales. The telson, (tail) was expanded, or flatter than it was tall. Pterygotidae also had chelicerae (claws in front of the mouth) that were large and long, with strong, well developed teeth on the claws. Their walking legs were small and slender, without spines.[5] They were the largest arthropods to have ever lived; the largest described fragments shows individuals up to 250 cm in length.[6][7] The pterygotids had good binocular vision and chelicerae adapted for cutting or crushing, making them some of the most formidable predators of the Paleozoic. A recent paper from Yale on the other hand speculated that Pterygotids may have been scavengers or hunted in dark waters based on their finding that Pterygotids had poor eyesight.[8]

Genera

Phylogeny

The genus Slimonia is thought to represent the sister group to the pterygotids.[6] Although the clade Pterygotidae is one of the best supported within the Eurypterida, relationships within the clade have been difficult to resolve.

Pterygotida[Node 1] 
[Node 2]

Erettopterus


[Node 4]

Pterygotus


[Node 3]

Acutiramus




Jaekelopterus






The interrelationships of the pterygotids, based on studies by Braddy et al.[6] and Tetlie and Briggs;[3] the synapomorphies are as follows:
  1. Chelicerae enlarged, walking appendages long, serrated podomere margins lost, pretelson with median dorsal carina
  2. Bilobed telson, undifferentiated denticles
  3. Large angular denticle on the fixed ramus of the chelicerae
  4. Telson with a posterior spine

References

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  8. http://news.yale.edu/2014/07/09/extinct-sea-scorpion-gets-yale-eye-exam-surprising-results