| Scanisaurus | |
|---|---|
_and_lower_back_(bottom)_vertebrae.png) | |
| Neck (top) and lower back (bottom) vertebrae referred toScanisaurus sp., excavated in theKristianstad Basin | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | †Sauropterygia |
| Order: | †Plesiosauria |
| Superfamily: | †Plesiosauroidea |
| Family: | †Elasmosauridae |
| Genus: | †Scanisaurus Persson, 1959 |
| Species: | †S. nazarowi |
| Binomial name | |
| †Scanisaurus nazarowi (Bogolyubov, 1911) | |
| Synonyms | |
| |
Scanisaurus is adubiousgenus ofplesiosaur that lived in what is now Sweden and Russia during theCampanian stage of theLate Cretaceous period. The nameScanisaurus means "Skåne lizard", Skåne being the southernmost province of Sweden, where a majority of the fossilsreferred to the genus have been recovered. The genus contains one species,S. nazarowi, described in 1911 byNikolay Bogolyubov as a species ofCimoliasaurus based on a singlevertebral centrum discovered nearOrenburg, Russia. the species was moved into its own genus by Per-Ove Persson in 1959 after several differences were observed between the Russian centra and new fossils from Skåne and the type species ofCimoliasaurus. Due to the limited type material and the lack of diagnostic features in the Swedish fossils confidently separatingScanisaurus from other Late Cretaceouselasmosaurids, the genus is of questionable validity, though it continues to be used in practice.
Scanisaurus fossils have mainly been found in theKristianstad Basin in northeastern Skåne, where they represent the most common plesiosaur fossils.Scanisaurus shared its environment with a diverse marine fauna, including many other marine reptiles. It would have been a middletrophic-level predator, about 4–5 meters (13–16 ft) in length, and would have been able to feed both in open water and on the sea floor, likely feeding mainly on small prey such as small fish orbelemnites.
In 1911, Russian paleontologistNikolay Bogolyubov described a Late Cretaceousposteriorcervical (neck)vertebral centrum discovered nearOrenburg, Russia. Bogolyubovreferred the centrum to the plesiosaur genusCimoliasaurus and believed it to represent a new species, which he namedC. nazarowi.[1] Bogolyubov compared the centrum with those of other plesiosaurs and found it to be most similar to a vertebra referred toCimoliasaurus sp. from theCenomanianQuiriquina Formation ofQuiriquina Island, Chile and to vertebrae referred toCimoliasaurus magnus, thetype species ofCimoliasaurus.[2] The main distinguishing feature used by Bogolyubov to justify the creation of a new species was that his centrum was wider than other centra referred toCimoliasaurus.[3]
In 1959, Swedish paleontologist Per-Ove Persson examined the fragmentary plesiosaur fossil record of Late CretaceousSkåne in southern Sweden, primarily recovered from fossil sites within theKristianstad Basin (many from the island ofIvö) and from south-western Skåne. He found that cervical vertebral centra from Skåne accorded so well with the vertebra described by Bogolyubov that they "must belong to one and the same genus". Furthermore, Persson noted several differences between Bogolyubov's centrum and the Swedish material and the fossils ofC. magnus, and consideredC. nazarowi distinct enough to warrant being placed in a separate genus. Persson named this new genusScanisaurus, meaning "Skåne lizard".[1] Persson noted thatS. nazarowi remained an "undefinable" species since it remains based on only a single vertebral centrum, but felt confident that the Swedish material was referrable to the species since it did not differ in any essential points from Bogolyubov's fossil.[4] Persson noted that the Swedish fossils were the same species "with a fairly great degree of probability" and provisionally designated them asS. cf.nazarowi.[5]
There were three principal characteristics Persson perceived to differentiateScanisaurus fromCimoliasaurus. First, inCimoliasaurus, the ribs were fused to the vertebrae with at least the pre-pectoral centra, whilst inScanisaurus the cervical ribs were fused to the centra by only the sutures. Second, the length of the posterior cervical centra decreased towards the head inCimoliasaurus, while the opposite was true inScanisaurus. Third, the cervical centra ofScanisaurus were broader proportional to their length than the corresponding centra ofCimoliasaurus.[1]
Because centra referred toS. cf.nazarowi were far more common in the Swedish fossil sites compared to centra from other plesiosaurs, Persson concluded thatS. cf.nazarowi was "obviously the most common plesiosaurian" in Late Cretaceous Skåne. With this in mind, he also referred the most common type of plesiosaur teeth found, some of which had been found in association withS. cf.nazarowi vertebrae, to the species as well, alongside associatedossifications ofhumeri andfemora.[6]
In 1995, in an examination of material referred to the invalid speciesPlesiosaurus houzeaui (found in Belgium), French paleontologist Nathalie Bardet and Belgian paleontologistPascal Godefroit discussed other questionable plesiosaur species from Europe. Bardet and Godefroit noted that though Persson had referred the Swedish material to several different elasmosaurid genera, includingScanisaurus andElasmosaurus, the fossils only possessed the necessary characteristics to be referred to the Elasmosauridae, not a particular genus or species. Though the material referred toS. cf.nazarowi, consisting of vertebrae, teeth and limb bones, was more complete than the material referred toElasmosaurus, it was deemed to lack any diagnostic features with which it could be differentiated from other Late Cretaceous elasmosaurids.[7] ThoughScanisaurus for this reason is typically no longer considered a valid taxon (constituting anomen dubium), the name continues to be used in practice.[8]
In 1996, Persson provisionally referred a crushed reptile skull recovered from Ignaberga quarry in the Kristianstad Basin toScanisaurus sp., since two tooth fragments associated with the fossil showed the same striation pattern as in the teeth referred toS. cf.nazrowi. Though the skull is too crushed to give much useful anatomical information, it is the only cranial fossil referred toScanisaurus (with the exception of teeth) and demonstrates that its head was comparatively larger than the heads of other dolichodiran plesiosaurs.[9]
Scanisaurus was a "dolichodiran" (i.e. long-necked) plesiosaur, albeit one with a neck relatively shorter than those of some of its relatives (such asElasmosaurus).[1] It has sometimes been described as a "mesodiran" plesiosaur, with a larger head and shorter neck relative to other dolichodiran genera.[10] It was likely similar to other relatively short-necked elasmosaurids, such asCimoliasaurus and the genera in the subfamilyAristonectinae.[11] Based on the size of its fossils and comparisons with the proportions of other plesiosaurs,Scanisaurus probably reached 4–5 meters (13–16 ft) in length.[12]
Persson wrote that most of the known characteristicsScanisaurus agreed well with the characteristics of the Elasmosauridae. However, Persson did not consider the genus to represent a typical elasmosaurid and noted that it differed in one essential feature; the cervical centra ofScanisaurus were shorter and broader than those of other elasmosaurids. With this in mind, Persson suggested thatScanisaurus could be a representative of a new family of Late Cretaceous plesiosaurs, possibly a group intermediate between pliosaurs such as thepolycotylids and elasmosaurids. BecauseScanisaurus was far more similar to elasmosaurids than it was to polycotylids, Persson provisionally referred the genus to the Elasmosauridae.[5]
In 1960, Persson referred bothCimoliasaurus andScanisaurus to a new family of mesodiran plesiosaurs, which he dubbed the Cimoliasauridae.[10] In 1963, Persson also referredAristonectes to the Cimoliasauridae on account of perceived close resemblances with fossil material ofCimoliasaurus andScanisaurus in the length-width ratio of the cervical centra.[13] Cimoliasauridae was placed as the sister group to Polycotylidae,[14] but a 2009 revision of the type fossils ofCimoliasaurus by American paleontologist F. Robin O'Keefe and Canadian paleontologist Hallie P. Street showed thatCimoliasaurus belonged to the Elasmosauridae, making the Cimoliasauridae synonymous with the Elasmosauridae.[15] A 2011 re-examination of the cervical vertebrae referred toScanisaurus by Swiss paleontologist Christian Foth and German paleontologists Johannes Kalbe and René Kautz suggested thatScanisaurus being placed in the Elasmosauridae was plausible. The well-defined ossified articular margins and binocular-shaped articular faces of the centra, combined with their relatively short length, are features shared betweenScanisaurus and other elasmosaurids.[14] Modern research thus tends to placeScanisaurus in the Elasmosauridae, though its precise position within the family is uncertain.[11][16]
A 2017 study by Swedish paleontologists Benjamin P. Kear, Dennis Larsson and Johan Lindgren and Slovak paleontologist Martin Kundrát interpretedScanisaurus as a middletrophic-level predator that would have been able to feed both in open water and on the sea floor.[17][18] Kear and colleagues drew this conclusion from the fact that elasmosaurid teeth were both structurally fragile and took more time to replace than the teeth of other reptiles, meaning that elasmosaurids such asScanisaurus would probably have kept to easily subdued prey to minimize the potential for damage, making them ecologically optimized towards middle trophic level aquatic predation.[18] The sharp and elongated teeth ofScanisaurus indicates that they were used to smash or pierce smaller prey such as small fish orbelemnites. Stomach content from other plesiosaurs has revealed a wide variety of prey, including bottom-dwelling invertebrates (i.e.gastropods andbivalves), fish,pterosaurs andammonites.[19]
Most of the fossils referred toScanisaurus cf.nazarowi have been recovered from fossil sites within the Kristianstad Basin, where, according to Persson,S. cf.nazarowi fossils represent the most common plesiosaur fossils found.[6][8] During theCampanian, the Kristianstad Basin was asubtropical totemperate shallow inland sea home to a diverse marine fauna characteristic of shallow marine life of an inner shelf community and included abundantalgae,brachiopods,bryozoans,molluscs (including bivalves, gastropods, belemnites and the ammonites),sea urchins,serpulids,decapods andsponges.[20][21] Additionally, fish (including a vast array ofsharks) were also common and fossils of many species of reptiles, most of them marine, have also been found, includingmosasaurs,sea turtles,crocodylomorphs and a fewdinosaurs.[22] There were also three to five other plesiosaur species (two species historically attributed toElasmosaurus, one or two polycotylids and potentially another species ofScanisaurus, represented by the 1996 skull and isolated teeth).[23] Mosasaur bite marks have been found on plesiosaur bones recovered from the basin.[24]
A fountain by the nameScanisaurus was constructed inBromölla, a town close to Ivö, by artistGunnar Nylund in 1971. The fountain depicts two plesiosaurs, one male and one female, sunbathing on a rock on the ancient Ivö island. The sculptures are made of around 3000 parts of shaped ceramics on bodies made of reinforced concrete. Locally in Sweden, plesiosaurs andScanisaurus in particular are often referred to as "svanödlor" ("swan lizards") or "svanhalsödlor" ("swan-neck lizards").[25]
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