Eurycleidus

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.

Eurycleidus
Temporal range: Early Jurassic,
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: †Sauropterygia
Order: †Plesiosauria
Family: †Rhomaleosauridae
Genus: †Eurycleidus
Andrews, 1922
Type species
†Eurycleidus arcuatus
(Owen, 1840)
Synonyms

Phylogeny

Most phylogenetic analyses find the type species of the genus, Eurycleidus arcuatus, to be a relatively basal rhomaleosaurid.[1][2][3][4] A second species, E. megacephalus (Stutchbury, 1846 [originally Rhomaleosaurus megacephalus]), was reassigned 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][4][5] 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

References
  1. Roger B. J. Benson; Mark Evans & 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. Bibcode:2012PLoSO...731838B. 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.
  3. Adam S. Smith; Gareth J. Dyke (2008). "The skull of the giant predatory pliosaur Rhomaleosaurus cramptoni: implications for plesiosaur phylogenetics" (PDF). Naturwissenschaften. 95 (10): 975–980. Bibcode:2008NW.....95..975S. doi:10.1007/s00114-008-0402-z. PMID 18523747. S2CID 12528732.
  4. Hilary F. Ketchum; 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.
  5. Roger B. J. Benson; Hilary F. Ketchum; Leslie F. Noè; 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.
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