Eretmosaurus

Eretmosaurus; Temporal range: Early - Middle Jurassic, 199.5–161.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Neotype specimen of E. rugosus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Plesiosauria
Family:	†Microcleididae
Genus:	†Eretmosaurus; Seeley, 1874
Type species
	†Eretmosaurus rugosus; Seeley, 1874
Other species
	†E. dubius Blake in Tate & Blake, 1876;
Synonyms
	Erethmosaurus von Huene, 1956; Plesiosaurus dubius Tate & Blake, 1876; Plesiosaurus rugosus Owen, 1840;

Eretmosaurus (meaning "oar lizard") is an extinct genus of plesiosaur from the Early and Middle Jurassic of England and Russia.^[1]^[2] Two species are known: E. rugosus and E. dubius.

History

Eretmosaurus rugosus

c. 1870 illustration of the holotype of *E. rugosus*

The holotype of E. rugosus consists of vertebrae, girdles, and limb bones and was discovered along Aust Cliff, where the Westbury Formation outcrops. Specimen BRSMB Cb 2458 was also assigned to the species by Owen (1840).^[3] This specimen later became the syntype and it consisted of several vertebrae that had been discovered at different locations in the Blue Lias in Gloucestershire.

Owen (1840) was the first to describe the specimens, which were named as Plesiosaurus rugosus.^[3] Later, Owen (1865) described a headless skeleton discovered in the Ammonites stellaris zone of the Blue Lias at Granby, Nottinghamshire (NHMUK 14435) that he assigned to P. rugosus,^[4] and Seeley used NHMUK 14435 as the basis for naming Eretmosaurus rugosus in 1874.^[5]

As BRSMB Cb 2458 was not diagnostic and was lost by 1940, a petition was filed with the ICZN over the holotype by Brown and Bardet (1994),^[1] and NHMUK 14435 was allocated as the official neotype in 1996.^[6]

A fragmentary specimen of Eretmosaurus rugosus has also been identified from the Middle Jurassic of Siberia by Menner (1992).^[2]

Eretmosaurus dubius

A partial skull and skeleton belonging to a plesiosaur was discovered in the Harpoceras faleifer zone, Whitby, England and it was initially described by Blake & Tate (1876) as a species of Plesiosaurus known as P. dubius. It was later reclassified as a species of Eretmosaurus by Blake in Blake & Tate (1876).^[7]

Other species

Benton and Spencer (1995) mentioned a third species of Eretmosaurus: E. macropterus; they rectified this mistake within the same paper by mentioning on page 116 that E. macropterus actually belongs to Microcleidus.^[8]

Classification

Eretmosaurus was classified into Rhomaleosauridae by Persson (1963),^[9] then into Pliosauridae by Brown (1981),^[10] then into Elasmosauridae by Bardet (1995)^[11] and Bardet et al. (1999),^[12] and most recently into Microcleididae by Benson et al. (2012).^[13]

References

^ ^a ^b David S. Brown and Nathalie Bardet (1994). Plesiosaurus rugosus Owen, 1840 (currently Eretmosaurus rugosus, Reptilia, Plesiosauria) proposed designation of a neotype. Bulletin of Zoological Nomenclature 51(3)
^ ^a ^b Menner, V. V. (1992). "Remains of Plesiosaurs from Middle Jurassic Deposits of Eastern Siberia". Russian Academy of Sciences, Department of Geology, Geophysics, Geochemistry and Mining Sciences, Order of the Red Manner of Labour Geological Institute: 74–91.
^ ^a ^b R. Owen. (1840). Report on British fossil reptiles. Report of the Ninth Meeting of the British Association for the Advancement of Science, Reports on the State of Science 43-126
^ R. Owen. (1865). A monograph of the fossil Reptilia of the Liassic formations. Part I, Sauropterygia. Palaeontographical Society Monographs 17(75):1-40
^ Seeley, H. G., (1874), Note on some of the generic modifications of the plesiosaurian pectoral arch: Quarterly Journal of the Geological Society of London, 1874, p. 436-449.
^ David S. Brown and Nathalie Bardet (1996). Plesiosaurus rugosus Owen, 1840 (currently Eretmosaurus rugosus, Reptilia, Plesiosauria) neotype designated. Bulletin of Zoological Nomenclature 53(1)
^ Blake, John F.; Tate, Ralph (1876). The Yorkshire Lias. University of California. ISBN 9789333163415.
^ Benton, M. J. and Spencer, P. S. (1995). Fossil reptiles of Great Britain. Chapman and Hall, London, 386 pp.
^ Persson, P.O. (1963): A revision of the classification of the Plesiosauria, with a synopsis of the stratigraphical and geographical distribution of the group. University of Lunds Årsskrift 59, No. 1, p. 1-57.
^ Brown, D. S. (1981). The English Upper Jurassic Plesiosauroidea (Reptilia) and a review of the phylogeny and classification of the Plesiosauria. Bulletin of the British Museum (Natural History): Geology, 35, (4), 253-347.
^ Bardet, N. (1995). Evolution et extinction des reptiles marins au cours du Mésozoïque. Palaeovertebrata, 24, 177-283.
^ Bardet, N.; Godefroit, P.; and Sciau, J. (1999). A new elasmosaurid plesiosaur from the Lower Jurassic of Southern France. Palaeontology'", 42, (5), 927-952.
^ Benson, Roger B. J.; Evans, Mark; Druckenmiller, Patrick S. (2012-03-16). Lalueza-Fox, Carles (ed.). "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. ISSN 1932-6203. PMC 3306369. PMID 22438869.