''Seeleyosaurus'' is an extinct
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
plesiosaur
The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia.
Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...
from
Germany
Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
and possibly also
Russia
Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
.
Two species were known: the
type
Type may refer to:
Science and technology Computing
* Typing, producing text via a keyboard, typewriter, etc.
* Data type, collection of values used for computations.
* File type
* TYPE (DOS command), a command to display contents of a file.
* ...
, ''S. guilelmiimperatoris'', and the now obsolete species ''S. holzmadensis'',
[White, T. E. (1940). Holotype of '']Plesiosaurus
''Plesiosaurus'' (Greek: ' ('), near to + ' ('), lizard) is a genus of extinct, large marine sauropterygian reptile that lived during the Early Jurassic. It is known by nearly complete skeletons from the Lias of England. It is distinguishable by ...
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
The Toarcian is, in the International Commission on Stratigraphy, ICS' geologic timescale, an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic. It spans the time between 184.2 Megaannum, Ma (million ...
)
Lias Group Formations of
Württemberg
Württemberg ( ; ) is a historical German territory roughly corresponding to the cultural and linguistic region of Swabia. The main town of the region is Stuttgart.
Together with Baden and Province of Hohenzollern, Hohenzollern, two other histo ...
, Germany. It was offered for sale by Bernard Hauff and it was purchased by the
State Museum of Natural History Stuttgart
The State Museum of Natural History Stuttgart (), abbreviated SMNS, is one of the two state of Baden-Württemberg's natural history museums. Together with the State Museum of Natural History Karlsruhe (Staatliches Museum für Naturkunde Karls ...
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 later 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.
The holotype was destroyed in 1945.
''Seeleyosaurus'' was initially described as ''
Plesiosaurus
''Plesiosaurus'' (Greek: ' ('), near to + ' ('), lizard) is a genus of extinct, large marine sauropterygian reptile that lived during the Early Jurassic. It is known by nearly complete skeletons from the Lias of England. It is distinguishable by ...
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
Zell unter Aichelberg is a municipality in the district of Göppingen (district), Göppingen in Baden-Württemberg in southern Germany.
Geographical location
Between Stuttgart and Ulm, on the western edge of the district Göppingen, lies the muni ...
, 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
Bernhard is both a given name and a surname. Notable people with the name include:
Given name
*Bernhard of Saxe-Weimar (1604–1639), Duke of Saxe-Weimar
* Bernhard, Prince of Saxe-Meiningen (1901–1984), head of the House of Saxe-Meiningen 194 ...
. 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.
A fragmentary specimen of ''Seeleyosaurus guilelmiimperatoris'' has also been identified from the
Middle Jurassic
The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...
of
Siberia
Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...
by Menner (1992).
Description
''Seeleyosaurus'' was a relatively small plesiosaur, measuring long.
Classification
The following
cladogram
A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
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''.
Gallery
File:SeeleysaurusDB.jpg, Restoration
File:Seleyosaurus holotype 1895.png, Holotype of ''S. guilelmiimperatoris'' in 1895
See also
*
List of plesiosaur genera
This list of plesiosaurs is a comprehensive listing of all genera that have ever been included in the order Plesiosauria, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered inv ...
*
Timeline of plesiosaur research
This timeline of plesiosaur research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, Taxonomy (biology), taxonomic revisions, and cultural portrayals of plesiosaurs, an order of marine reptiles ...
References
Early Jurassic plesiosaurs of Europe
Plesiosauroids
Sauropterygian genera
Fossil taxa described in 1940
Toarcian first appearances
{{plesiosaur-stub