Seeleyosaurus
{{short description|Genus of reptiles (fossil)}}
{{Automatic taxobox
| fossil_range = Early Jurassic, {{fossilrange|Toarcian|latest=Middle Jurassic}}
| image = Seeleyosaurus guilelmiimperatoris 2.JPG
| image_upright = 1.15
| image_caption = Cast of Seeleyosaurus guilelmiimperatoris fossil with reconstructed parts based on the holotype
| taxon = Seeleyosaurus
| authority = White, 1940
| type_species = {{extinct}}Seeleyosaurus guilelmiimperatoris
| type_species_authority = (Dames, 1895)
| synonyms = *Microcleidus guilelmi imperatoris Menner, 1992
- Plesiosaurus guilelmi imperatoris Fraas, 1910 non Dames, 1895
- Plesiosaurus imperatoris guilelmi Menner, 1992
- Plesiosaurus guilelmiimperatoris Dames, 1895
- Seeleyosaurus holzmadensis White, 1940
}}
Seeleyosaurus is an extinct genus of plesiosaur from Germany and possibly also Russia.
Two species were known: the type, S. guilelmiimperatoris, and the now obsolete species S. holzmadensis,White, T. E. (1940). Holotype of Plesiosaurus longirostris Blake and classification of the plesiosaurs. Journal of Paleontology 14(5):451-467 which has since been absorbed into S. guilelmiimperatoris.
Discovery and naming
The holotype is MB.R.1992, a large almost complete skeleton from the Upper Lias (Toarcian) Lias Group Formations of Württemberg, Germany. It was offered for sale by Bernard Hauff and it was purchased by the State Museum of Natural History Stuttgart in August 1893.Dames, H. W. (1895). Die Plesiosaurier der süddeutschen Liasformation. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 2:1-83 It preserved soft tissue that was painted over around ten years laterWilhelm, B. (2010). Novel anatomy of cryptoclidid plesiosaurs with comments on axial locomotion. M.S. thesis, Marshall University, Huntington, West Virginia, 76 pp. and a cast of the holotype was described in by Ketchum & Benson (2011), who determined that it seems to preserve the impression of a rhomboidal flap of skin in a vertical plane, suggesting that many other plesiosaurs may have been equipped in this way.{{cite journal |last1=Ketchum |first1=Hillary F. |last2=Benson |first2=Roger B.J. |year=2011 |title=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 |url=https://www.palass.org/publications/special-papers-palaeontology/archive/86/article_pp109-129 |journal=Special Papers in Palaeontology |volume=86 |pages=109–129}} The holotype was destroyed in 1945.
Seeleyosaurus was initially described as Plesiosaurus guilelmiimperatoris by Dames (1895) before White (1940) moved P. guilelmiimperatoris to its own genus. White (1940) also assigned a second species to Seeleyosaurus as S. holzmadensis which was later determined to be the same animal as S. guilelmiimperatoris.
A second specimen (SMNS 12039), preserved in 3D, was initially the holotype of S. holzmadensis. It was discovered within a chalkstone and shale quarry located between Holzmaden and Zell unter Aichelberg, and it intersected an extremely hard forty centimetres thick layer of Stinkstein chalk, which was deemed worthless. The rocks were dumped in a ravine and the holotype was discovered there in November 1906 by fossil trader Bernhard Hauff. Alongside the holotype of Meyerasaurus victor, it was offered for sale, and financial support by D. Landauer and Victor Fraas allowed the Stuttgarter Königliche Naturalienkabinett to obtain both specimens.{{cite journal |last=Fraas |first=Eberhard |year=1910 |title=Plesiosaurier aus dem oberen Lias von Holzmaden |url=https://www.zobodat.at/pdf/Palaeontographica_57_0105-0140.pdf |journal=Palaeontographica |volume=57 |issue=3–4 |pages=105-140}}
A fragmentary specimen of Seeleyosaurus guilelmiimperatoris has also been identified from the Middle Jurassic of Siberia by Menner (1992).{{Cite journal |last=Menner |first=V. V. |date=1992 |title=Remains of Plesiosaurs from Middle Jurassic Deposits of Eastern Siberia |journal=Russian Academy of Sciences, Department of Geology, Geophysics, Geochemistry and Mining Sciences, Order of the Red Manner of Labour Geological Institute |pages=74-91}}
Description
Seeleyosaurus was a relatively small plesiosaur, measuring {{cvt|2.9|-|3.6|m|ft}} long.{{Cite journal |author=Peggy Vincent |year=2011 |title=A re-examination of Hauffiosaurus zanoni, a pliosauriod from the Toarcian (Early Jurassic) of Germany |journal=Journal of Vertebrate Paleontology |volume=31 |issue=2 |pages=340–351 |bibcode=2011JVPal..31..340V |doi=10.1080/02724634.2011.550352 |s2cid=84743241}}{{Cite journal |author1=Valentin Fischer |author2=Nikolay G. Zverkov |author3=Maxim S. Arkhangelsky |author4=Ilya M. Stenshin |author5=Ivan V. Blagovetshensky |author6=Gleb N. Uspensky |year=2020 |title=A new elasmosaurid plesiosaurian from the Early Cretaceous of Russia marks an early attempt at neck elongation |url=https://orbi.uliege.be/handle/2268/251614 |journal=Zoological Journal of the Linnean Society |volume=192 |issue=4 |pages=1167–1194 |doi=10.1093/zoolinnean/zlaa103 |hdl=2268/251614}}[https://orbi.uliege.be/bitstream/2268/251614/2/Supp_info.pdf Supplementary Information]
Classification
The following cladogram follows an analysis by Ketchum & Benson, 2011.
A redescription and a study on the affinities of Seeleyosaurus guilelmiimperatoris published by Sachs et al. (2025) interpreted Plesiopterys wildi as a taxon distinct from S. guilelmiimperatoris.{{Cite journal |last1=Sachs |first1=S. |last2=Madzia |first2=D. |last3=Marx |first3=M. |last4=Roberts |first4=A. J. |last5=Hampe |first5=O. |last6=Kear |first6=B. P. |year=2025 |title=The osteology, taxonomy, and phylogenetic placement of Seeleyosaurus guilelmiimperatoris (Plesiosauroidea, Microcleididae) from the Lower Jurassic Posidonia Shale of Germany |journal=The Anatomical Record |doi=10.1002/ar.25620 |pmid=39981975}}Gallery
File:SeeleysaurusDB.jpg|Restoration
File:Seleyosaurus holotype 1895.png|Holotype of S. guilelmiimperatoris in 1895
File:Image from page 85 of "Water reptiles of the past and present" (1914) (14749985076).jpg|Seeleyosaurus (left) and Thaumatosaurus, now Meyerasaurus (right) as depicted in Water reptiles of the past and present (1914)
See also
{{Portal|Paleontology}}
References
{{Sauropterygia|Pliosauroidea}}
{{Taxonbar|from=Q7445837}}
Category:Early Jurassic plesiosaurs of Europe
Category:Sauropterygian genera
Category:Fossil taxa described in 1940
Category:Toarcian first appearances
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