''Ceresiosaurus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

aquatic

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 lariosaurine

nothosaurid Nothosauridae are an extinct family of carnivorous aquatic sauropterygian reptiles from the Triassic time period of China, France, Germany, Israel, Italy, Netherlands, Russia, Switzerland, and northern Africa. Phylogeny The cladogram shown bel ...

sauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic diapsid reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosau ...

n known from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

(

Anisian In the geologic timescale, the Anisian is the lower stage (stratigraphy), stage or earliest geologic age, age of the Middle Triassic series (stratigraphy), series or geologic epoch, epoch and lasted from million years ago until million years ag ...

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

boundary) of

Monte San Giorgio Monte San Giorgio is a Swiss mountain and UNESCO World Heritage Site near the border between Switzerland and Italy. It is part of the Lugano Prealps, overlooking Lake Lugano in the Swiss Canton of Ticino. Monte San Giorgio is a wooded mountai ...

, southern

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

and northern

Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...

. Ceresiosaurus, meaning "Lizard of Ceresio" (Ceresio is the name of the

Lake Lugano Lake Lugano ( or , from ; ) is a glacial lake which is situated on the border between southern Switzerland and northern Italy. The lake, named after the city of Lugano, is situated between Lake Como and Lago Maggiore. It was cited for the first t ...

, in

). The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''Ceresiosaurus calcagnii'', was named by

Bernhard Peyer Bernhard Peyer (25 July 1885 – 23 February 1963) was a Swiss paleontologist and anatomist who served as a professor at the University of Zurich. A major contribution was on the evolution of vertebrate teeth. Peyer was born in Schaffhausen, Swit ...

1931 Events January * January 2 – South Dakota native Ernest Lawrence invents the cyclotron, used to accelerate particles to study nuclear physics. * January 4 – German pilot Elly Beinhorn begins her flight to Africa. * January 22 – Sir I ...

. ''C. calcagnii'' is known from both the Cava superiore and Cava inferiore beds of the Lower Meride Limestone at Monte San Giorgio, dating to the latest Anisian of the Middle Triassic. Rieppel (1998) suggested that the back then

monospecific In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

genus ''Ceresiosaurus'', is a

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

of the better known ''

Lariosaurus ''Lariosaurus'' is an extinct genus of nothosaurid from the Middle Triassic (late Anisian to late Ladinian stage) of central and western Europe and China. With a complete specimen of ''L. xingyiensis'' measuring long and ''L. hongguoensis'' poss ...

'', yet he kept it type species as a separate species under the new combination ''L. calcagnii''. In 2004, however, this synonymy was objected by Hänni who described and name a second species of ''Ceresiosaurus'', ''C. lanzi'' - a separation supported by several other authors since. This species is known only from the

stratigraphically Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostrati ...

younger Cassima beds of Monte San Giorgio, although also from the Lower Meride Limestone, dating to possibly the lowest

age. The species in a subtropical

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

al environment with varying open marine influences, and alongside many related but smaller species of

s and pachypleurosaurids. ''Ceresiosaurus'' represents one of the largest vertebrate of up to snout-tail length from the very diversified paleoenvironment of the Middle Triassic Monte San Giorgio.

Palaeobiology

''Ceresiosaurus'' was much more elongated than its relatives, reaching in length, and had fully developed flippers with no trace of visible toes. It had multiple elongated

phalanges The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three phalanges. ...

, making the flippers much longer than in most other nothosaurs, and more closely resembling those of the later

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 ...

s. ''Ceresiosaurus'' also had the shortest

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

of any known nothosaur, which further increased its resemblance to plesiosaurs. Although possessing a long neck and tail, ''Ceresiosaurus'' may not have swum by undulating its body. Analysis of the bone structure of the hips and powerful tail suggest that it instead propelled itself through the water much like a

penguin Penguins are a group of aquatic flightless birds from the family Spheniscidae () of the order Sphenisciformes (). They live almost exclusively in the Southern Hemisphere. Only one species, the Galápagos penguin, is equatorial, with a sm ...

. The evidence of

pachypleurosaur Pachypleurosauria is an extinct clade of primitive sauropterygian reptiles from the Triassic period. Pachypleurosaurs vaguely resembled aquatic lizards, with elongate forms ranging in size from , with small heads, long necks, paddle-like limbs, a ...

s in the preserved stomach of ''Ceresiosaurus'' remains lend credence to the theory of it being a fast swimmer.

References

External links

Palaeos.com
{{Authority control Nothosaurs Triassic sauropterygians Middle Triassic reptiles of Europe Anisian life Sauropterygian genera