Amphilestes

Amphilestes is a genus of extinct eutriconodont mammal from the Middle Jurassic of the United Kingdom. It was the first ever Mesozoic mammal discovered and described.

The first specimen of Amphilestes was discovered in the Stonesfield Slate Quarry, Oxfordshire before 1764. However, it was not until 1812 that William Broderip bought the jaws, and he and his mentor - the famous palaeontologist Revd William Buckland - recognised that they were of mammal origin.

Amphilestes is known from various dental and mandibular remains. The dental formula of the mandible is 4:1:4:5. The premolars are symmetrical and the crowns look like tricusped molars, with the central cusp being largest in premolars and molars, though the size difference is less great in the premolars. George Gaylord Simpson (1928, p. 71) noted that the teeth of Amphilestes are diagnosable in having “molar cusps high and slender, molar cingulum rising below the main cusp, molar enamel not pitted."