Pterygotidae

Pterygotidae Temporal range: Llandovery – Early Devonian PreЄ Є O S D C P T J K Pg N
Reconstruction of Acutiramus
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Class:	Merostomata
Order:	†Eurypterida
Suborder:	†Eurypterina
Superfamily:	†Pterygotioidea
Family:	†Pterygotidae Clarke & Ruedemann, 1912
Genera
See text
Synonyms
†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.

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] 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.^[8]

Genera

• Class Merostomata Dana, 1852
• Order Eurypterida Burmeister, 1843
• Suborder Eurypterina Burmeister, 1843
• Superfamily Pterygotioidea Clarke & Ruedemann, 1912

  Family Pterygotidae Clarke & Ruedemann, 1912

  Genus Acutiramus Ruedemann, 1935

  Genus Ciurcopterus Tetlie & Briggs, 2009

  Genus Erettopterus Salter in Huxley & Salter, 1859

  Genus Jaekelopterus Waterston, 1964

  Genus Pterygotus Agassiz, 1839

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 3] Pterygotus [Node 4] 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: Chelicerae enlarged, walking appendages long, serrated podomere margins lost, pretelson with median dorsal carina Bilobed telson, undifferentiated denticles Telson with a posterior spine Large angular denticle on the fixed ramus of the chelicerae

References

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. 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. 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 2412931. PMID 18029297.
7. Jason A. Dunlop, David Penney, O. Erik Tetlie & Lyall I. Anderson (2008). "How many species of fossil arachnids are there?" (PDF). Journal of Arachnology 36 (2): 267–272. doi:10.1636/CH07-89.1.
8. 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. <http://rsbl.royalsocietypublishing.org/content/11/8/20150564>.