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

See text


Jaekelopteridae Størmer, 1974

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.


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 540 cm in length.[6] Some of the pterygotids had reasonable binocular vision and chelicerae adapted for cutting or crushing, making them some of the most formidable predators of the Paleozoic. Others had poor eyesight and chelicerae more adapted to slicing, and so, most likely either scavenged or fed on soft-bodied organisms.[7]



The genus Slimonia is thought to represent the sister group to the pterygotids.[8] Although the clade Pterygotidae is one of the best supported within the Eurypterida, relationships within the clade have been difficult to resolve.

Pterygotida[Node 4] 
[Node 1]


[Node 3]


[Node 2]



The interrelationships of the pterygotids, based on studies by Braddy et al.[8] and Tetlie and Briggs;[3] the synapomorphies are as follows:
  1. ^ Bilobed telson, undifferentiated denticles
  2. ^ Large angular denticle on the fixed ramus of the chelicerae
  3. ^ Telson with a posterior spine
  4. ^ Chelicerae enlarged, walking appendages long, serrated podomere margins lost, pretelson with median dorsal carina


  1. ^ Alfred S. Romer (1993). "Eurypterid influence on vertebrate history". Science. 78 (2015): 114–117. doi:10.1126/science.78.2015.114. PMID 17749819. 
  2. ^ O. Erik Tetlie (2007). "Distribution and dispersal history of Eurypterida (Chelicerata)" (PDF). Palaeogeography, Palaeoclimatology, Palaeoecology. 252 (3–4): 557–574. doi:10.1016/j.palaeo.2007.05.011. 
  3. ^ a b O. Erik Tetlie & Derek E. G. Briggs (2009). "The origin of pterygotid eurypterids (Chelicerata: Eurypterida)". Palaeontology. 52 (5): 1141–1148. doi:10.1111/j.1475-4983.2009.00907.x. 
  4. ^ D. E. G. Briggs; R. A. Fortey; E. N. K. Clarkson (1998). "Extinction and the fossil record of arthropods". In Gilbert Powell Larwood. Extinction and survival in the fossil record. Systematics Association. pp. 171–209. ISBN 978-0-19-857708-9. 
  5. ^ L. Størmer (1955). "Merostomata". Treatise on Invertebrate Paleontology, Part P Arthropoda 2, Chelicerata. p. 23. 
  6. ^
  7. ^ McCoy, Victoria E., James C. Lamsdell, Markus Poschmann, Ross P. Anderson, and Derek E. G. Briggs. "All the better to see you with: eyes and claws reveal the evolution of divergent ecological roles in giant pterygotid eurypterids." Royal Society Publishing. 19 Aug. 2015. Web. <>.
  8. ^ a b Simon J. Braddy, Markus Poschmann & O. Erik Tetlie (2008). "Giant claw reveals the largest ever arthropod". Biology Letters. 4 (1): 106–109. doi:10.1098/rsbl.2007.0491. PMC 2412931Freely accessible. PMID 18029297.