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]
| Eurycleidus Temporal range: Early Jurassic,
| |
|---|---|
Scientific 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 | |
| |
Discovery and naming
The known remains consist of syntypes BMNH 2027, 2028, 2029, 2030, and associated specimens BMNH R.1317 en R.1318, BMNH 2047, BMNH 2061 and BMNH R.1319. They were acquired by Thomas Hawkins during the early 1830s from a quarry in Street, Somerset and he described them in 1834.[2]
In 1837, Richard Owen erroneously believed the remains had been found in Lyme Regis, and in 1840 he assigned them to Plesiosaurus under the newly created species P. arctuatus.[3]
In 1889 Richard Lydekker moved the species to the genus Thaumatosaurus as T. arcuatus.[4] Lydekker stated that specimen BMNH 2030, a symphysis of the lower jaws, was the holotype, although it can at most be a lectotype.[5] He believed that the other pieces belonged to the same individual, indicating that they could have been obtained from a continuous piece of rock and that there is no overlap in the elements (BMNH R2029 is a left coracoid, BMNH R2027 is a left femur and a vertebra, BMNH R1322 are the clavicles and the interclavicle and skull material was completely unknown at the time).
In 1922, Charles William Andrews, after the pectoral girdle had been re-prepared and exposed, named a separate genus Eurycleidus.[6]
In1932, Thaumatosaurus victor was renamed to Eurycleidus victor; it was moved to its own genus Meyerasaurus in 2010.
In 1994, the fairly complete skeleton OUM J.28585 was assigned to E. arcuatus. It was later moved to Atychodracon.[7]
A second species, E. megacephalus (Stutchbury, 1846 [originally Rhomaleosaurus megacephalus]), was reassigned to this genus by Smith (2007).[5] However, most analyses find E. megacephalus to represent an unnamed genus, which is distinct from both Eurycleidus and Rhomaleosaurus.[8][9][10] E. megacephalus was moved to its own genus Atychodracon by Adam Smith in 2015.[7]
A specimen discovered in 1899 in Halberstadt, Germany that was assigned to Eurycleidus arctuatus was moved to its own genus Lindwurmia in 2019.
Description
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, Plesiosaurus arcuatus Owen 1840,[3] with as combinatio nova EurycleA second species, E. megacephalus (Stutchbury, 1846 [originally Rhomaleosaurus megacephalus]), was reassigned to this genus by Smith (2007).[11] However, most analyses find E. megacephalus to represent an unnamed genus, which is distinct from both Eurycleidus and Rhomaleosaurus.[12][13][14] E. megacephalus was moved to its own genus Atychodracon by Adam Smith in 2015.[15]idus arcuatus Andrews 1922,[6] to be a relatively basal rhomaleosaurid.[1][5][8][9]
The cladogram below shows E. arcuatus phylogenetic position among other plesiosaurs following Benson et al. (2012).[1]
See also
References
- ^ a b c 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.
- ^ Hawkins, T.H. (1834). Memoirs on Ichthyosauri and Plesiosauri; Extinct monsters of the ancient Earth. Reife and Fletcher, London, 58 pp
- ^ a b Owen, R. (1840). Report on British fossil reptiles. Part I. Report of the British Association for the Advancement of Science 1839: 43-126
- ^ Lydekker, R. (1889). Catalogue of the fossil Reptilia and Amphibia in the British Museum (Natural History). Part II. Containing the orders Ichthyopterygia and Sauropterygia. British Museum (Natural History), London, 307 pp
- ^ a b c Adam S. Smith (2007). Anatomy and systematics of the Rhomaleosauridae (Sauropterygia, Plesiosauria) (Ph.D. thesis). University College Dublin.
- ^ a b C. W. Andrews. (1922). "Description of a new plesiosaur from the Weald Clay of Berwick (Sussex)". Quarterly Journal of the Geological Society 78: 285-298
- ^ a b Smith, Adam S. (22 April 2015). "Reassessment of Plesiosaurus' megacephalus (Sauropterygia: Plesiosauria) from the Triassic-Jurassic boundary, UK". Palaeontologia Electronica. 18 (1): 1–20.
- ^ a b 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.
- ^ a b 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.
- ^ 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.
- ^ Adam S. Smith (2007). Anatomy and systematics of the Rhomaleosauridae (Sauropterygia, Plesiosauria) (Ph.D. thesis). University College Dublin.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ Smith, Adam S. (22 April 2015). "Reassessment of Plesiosaurus' megacephalus (Sauropterygia: Plesiosauria) from the Triassic-Jurassic boundary, UK". Palaeontologia Electronica. 18 (1): 1–20.