A calculus is a solid mineral concretion such as a kidney stone, bladder stone, gall stone or stomach stone that forms naturally in a body under certain dietary or environmental conditions. Calculi that form in the gastrointestinal tract are enteroliths and these are often near-spherical objects, sometimes with a hollow centre, with a concentrically layered structure composed of radiating crystals oriented perpendicular to the surface. They are known in the archaeological record but are almost entirely absent from the fossil record, most likely due to them simply not being recognised for what they are. We describe a fossil calculus from the Upper Kimmeridge Clay (Upper Jurassic, , 150 million years old) marine deposit at Kimmeridge in Dorset, UK. This is the oldest calculus known from the fossil record with previous confirmed records from the terrestrial Oligocene of Colorado and the marine Upper Cretaceous Chalk of Germany: it extends the temporal range of known calculi in the fossil record by at least 59 million years. Although there are a wide range of potential hosts, the Kimmeridge calculus may have been produced by a large marine reptile.

中文翻译：

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化石记录中已知最古老的结石（胃肠道的肠石），来自英国金默里奇粘土地层（上侏罗纪）

结石是在某些饮食或环境条件下在体内自然形成的固体矿物质结核，例如肾结石、膀胱结石、胆结石或胃结石。胃肠道中形成的结石是肠石，它们通常是近球形物体，有时具有中空中心，具有由垂直于表面的辐射晶体组成的同心层状结构。它们在考古记录中是已知的，但在化石记录中几乎完全不存在，很可能是因为它们根本没有被认识到它们的本质。我们描述了来自英国多塞特郡基默里奇上基默里奇粘土（上侏罗纪，1.5 亿年前）海洋沉积物的化石。这是化石记录中已知的最古老的演算，之前已确认来自科罗拉多州陆地渐新世和德国海洋上白垩纪白垩的记录：它将化石记录中已知演算的时间范围延长了至少 5900 万年。尽管潜在宿主的范围很广，但金默里奇微积分可能是由大型海洋爬行动物产生的。