Peloneustes is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of sauropterygia

Sauropterygia

Sauropterygia were a group of very successful aquatic reptiles that flourished during the Mesozoic before they became extinct at the end of the era. They were united by a radical adaptation of their shoulder, designed to support powerful flipper strokes...

n reptile

Reptile

Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

 belonging to the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Pliosaur

Pliosaur

Pliosauroidea is an extinct clade of marine reptiles. Pliosauroids, also commonly known as pliosaurs, are known from the Jurassic and Cretaceous Periods. The pliosauroids were short-necked plesiosaurs with large heads and massive toothed jaws. These swimming reptiles were not dinosaurs but distant...

idae. It is known from the Callovian

Callovian

In the geologic timescale, the Callovian is an age or stage in the Middle Jurassic, lasting between 164.7 ± 4.0 Ma and 161.2 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian....

 aged (Middle Jurassic) deposits of the Oxford clay formation of England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. With a length of around 3 metres (9.8 ft), it was one of the smallest representatives of the group.
Like its larger relatives, Peloneustes had a short neck and long jaws capable of grabbing large prey. Its streamlined body allowed it to chase fast prey such as belemnites. As it had fewer and blunter teeth than its relatives, it is thought to have mainly fed on hard prey such as ammonite

Ammonite

Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...

s. It is often shown as being in the same waters as Liopleurodon

Liopleurodon

Liopleurodon is a genus of large, carnivorous marine reptile belonging to the Pliosauroidea, a clade of short-necked plesiosaurs. Two species of Liopleurodon lived during the Callovian stage of the Middle Jurassic Period , while the third, L. rossicus, lived during the Late Jurassic...