Pterygotidae

Pterygotidae
Temporal range: Llandovery – Early Devonian
Reconstruction of Acutiramus cummingsi
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
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] 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 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:
  1. ↑ Chelicerae enlarged, walking appendages long, serrated podomere margins lost, pretelson with median dorsal carina
  2. ↑ Bilobed telson, undifferentiated denticles
  3. ↑ Telson with a posterior spine
  4. ↑ 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. ↑ 3.0 3.1 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. ↑ 6.0 6.1 6.2 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. ↑ http://news.yale.edu/2014/07/09/extinct-sea-scorpion-gets-yale-eye-exam-surprising-results