''Simolestes'' (meaning "hearkening thief") is an extinct pliosaurid

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

that lived in the Middle to Late

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

. The type specimen, BMNH R. 3319 is an almost complete but crushed skeleton diagnostic to ''Simolestes vorax'', dating back to the Callovian of the Oxford Clay formation, England. The genus is also known from the Callovian and

Bajocian In the geologic timescale The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relatin ...

of France (''S.keileni''), and the

Tithonian In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by t ...

of India (''S.indicus''). The referral of these two species to ''Simolestes'' is dubious, however.

Description

''Simolestes'' possessed a short, high, and wide skull which was built to resist torsional forces when hunting. The largest specimens of ''S.vorax'' reached approximately in length, if a head to body ratio similar to ''

Liopleurodon ''Liopleurodon'' (; meaning 'smooth-sided teeth') is an extinct genus of large, carnivorous marine reptile belonging to the Thalassophonea, a clade of short-necked pliosaurid plesiosaurs. ''Liopleurodon'' lived from the Callovian Stage of the Mi ...

'' is applied. ''S.keileni'' was larger, with specimens from France suggesting that some individuals grew more than long. ''S. vorax'' and ''S. keileni'' weighed about , respectively.

Palaeobiology

Like most Pliosaurs, ''Simolestes'' possessed salt secreting glands, which would have enabled the animal to maintain salt balance and drink seawater.Noè, L. F. (2001). A taxonomic and functional study of the Callovian (Middle Jurassic) Pliosauroidea (Reptilia, Sauropterygia). Chicago Recent studies on Plesiosaur locomotion indicate that ''Simolestes'', like other Plesiosaurs, possessed a unique bauplan for movement, which differs from modern organisms in similar niches. Simolestes_skull_side1

Feeding habits

''Simolestess exact feeding habits are unclear. The current consensus, however, is that the genus was primarily teuthophagous, consuming

belemnites Belemnites may refer to: *Belemnitida Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. ...

, soft teuthoids and

ammonites Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttle ...

. It is possible ''Simolestes'' was also ecologically separated from other contemporary pliosaur genera such as ''Liopleurodon'' and '' Pachycostasaurus'' by hunting in deeper waters or at night, as modern cephalopods exhibit diurnal feeding cycles, spending daylight in deeper, safer waters, and rising at night to feed.

Classification

The

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

below follows a 2011 analysis by paleontologists Hilary F. Ketchum and Roger B. J. Benson, and reduced to genera only.

References

{{Taxonbar, from=Q311851 Pliosaurids Plesiosaurs of Asia Middle Jurassic plesiosaurs of Europe Late Jurassic plesiosaurs of Europe Oxford Clay Taxa named by Charles William Andrews Fossil taxa described in 1909 Sauropterygian genera