''Simolestes'' (meaning "snub-nosed thief") is an extinct pliosaurid

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 ...

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 143.1 Mya. ...

. The type specimen, NHMUK PV R 3319 is an almost complete but crushed skeleton diagnostic to ''Simolestes vorax'', dating back to the

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 165.3 ± 1.1 Ma (million years ago) and 161.5 ± 1.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...

of the

Oxford Clay The Oxford Clay (or Oxford Clay Formation) is a Jurassic marine sedimentary rock formation underlying much of southeast England, from as far west as Dorset and as far north as Yorkshire. The Oxford Clay Formation dates to the Jurassic, specific ...

formation, England. The genus might also be known from the

Tithonian In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...

Bhuj Formation of India (''S.indicus''), however the referral of this species to ''Simolestes'' is dubious. ''S.keileni'' from France was moved to the new genus '' Lorrainosaurus'' in 2023.

Description

''Simolestes'' possessed a short, high, and wide skull which was built to resist

torsional In the field of solid mechanics, torsion is the twisting of an object due to an applied torque. Torsion could be defined as strain or angular deformation, and is measured by the angle a chosen section is rotated from its equilibrium position. Th ...

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 carnivorous pliosaurid pliosaurs that lived from the Callovian stage of the Middle Jurassic to the Kimmeridgian stage of the Late Jurassic period (c. 166 to 155 mya). T ...

'' is applied.

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 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 ...

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, an extinct order of cephalopods commonly known as "belemnites" *Belemnites (genus), ''Belemnites'' (genus), a belemnite genus from the Early Jurassic {{disambiguation ...

, soft teuthoids and

ammonites Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

. It is possible ''Simolestes'' was also ecologically separated from other contemporary pliosaur genera such as ''Liopleurodon'' and ''

Pachycostasaurus ''Pachycostasaurus'' (meaning 'thick-ribbed lizard') is an extinct Pliosauroid from the Oxford Clay formation of Peterborough, England. History and naming The holotype fossil of ''Pachycostasaurus'' was discovered by Alan Dawn, an amateur geolog ...

'' 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 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 ...

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

References

{{Taxonbar, from=Q311851 Pliosauridae 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