Eurycleidus

Eurycleidus Temporal range: Early Jurassic, 199.6–198 Ma PreЄ Є O S D C P T J K Pg N ↓
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Plesiosauria
Family:	†Rhomaleosauridae
Genus:	†Eurycleidus Andrews, 1922
Type species
†Eurycleidus arcuatus (Owen, 1840 [originally Plesiosaurus arcuatus])

Eurycleidus is an extinct genus of large-bodied rhomaleosaurid known from the Early Jurassic period (most likely earliest Hettangian stage) of the United Kingdom. It contains a single species, E. arcuatus.^[1] Like other plesiosaurs, Eurycleidus probably lived on a diet of fish, using its sharp needle-like teeth to catch prey. Its shoulder bones were fairly large, indicating a powerful forward stroke for fast swimming.

Phylogeny

Most phylogenetic analyses find the type species of the genus, Eurycleidus arcuatus, to be a relatively basal rhomaleosaurid.^[2][3][4][1] A second species, E. megacephalus (Stutchbury, 1846 [originally Rhomaleosaurus megacephalus]), was re-assigned to this genus by Smith (2007).^[2] However, most analyses find E. megacephalus to represent an unnamed genus, which is distinct from both Eurycleidus and Rhomaleosaurus.^[3][5][4] E. megacephalus was moved to its own genus Atychodracon by Adam Smith in 2015.^[6]

The cladogram below shows E. arcuatus phylogenetic position among other plesiosaurs following Benson et al. (2012).^[1]

Plesiosauria	Neoplesiosauria  Pliosauridae Plesiosauroidea  Rhomaleosauridae  Stratesaurus taylori Macroplata tenuiceps Avalonnectes arturi Eurycleidus arcuatus Meyerasaurus victor Maresaurus coccai Atychodracon megacephalus Archaeonectrus rostratus Rhomaleosaurus cramptoni Rhomaleosaurus thorntoni Rhomaleosaurus zetlandicus

See also

• Timeline of plesiosaur research

• List of plesiosaurs

References

1. Roger B. J. Benson, Mark Evans and Patrick S. Druckenmiller (2012). "High Diversity, Low Disparity and Small Body Size in Plesiosaurs (Reptilia, Sauropterygia) from the Triassic–Jurassic Boundary". PLoS ONE 7 (3): e31838. doi:10.1371/journal.pone.0031838. PMC 3306369. PMID 22438869.
2. Adam S. Smith (2007). "Anatomy and systematics of the Rhomaleosauridae (Sauropterygia, Plesiosauria)". Ph.D. thesis, University College Dublin. line feed character in |journal= at position 33 (help)
3. Adam S. Smith and Gareth J. Dyke (2008). "The skull of the giant predatory pliosaur Rhomaleosaurus cramptoni: implications for plesiosaur phylogenetics" (PDF). Naturwissenschaften 95: 975–980. doi:10.1007/s00114-008-0402-z. PMID 18523747.
4. Hilary F. Ketchum and Roger B. J. Benson (2011). "A new pliosaurid (Sauropterygia, Plesiosauria) from the Oxford Clay Formation (Middle Jurassic, Callovian) of England: evidence for a gracile, longirostrine grade of Early-Middle Jurassic pliosaurids". Special Papers in Palaeontology 86: 109–129. doi:10.1111/j.1475-4983.2011.01083.x.
5. Roger B. J. Benson, Hilary F. Ketchum, Leslie F. Noè and Marcela Gómez-Pérez (2011). "New information on Hauffiosaurus (Reptilia, Plesiosauria) based on a new species from the Alum Shale Member (Lower Toarcian: Lower Jurassic) of Yorkshire, UK". Palaeontology 54 (3): 547–571. doi:10.1111/j.1475-4983.2011.01044.x.
6. Smith, Adam S. (22 April 2015). "Reassessment of ‘Plesiosaurus’ megacephalus (Sauropterygia: Plesiosauria) from the Triassic-Jurassic boundary, UK". Palaeontologia Electronica 18 (1): 1–20.