Evolutionary history of naticid shell-drilling predation

1.根据对一种活化石蜗牛Globularia fluctuata（Sowerby）的解剖学研究，这种蜗牛具有原始的神经系统，并具有许多与淡水壶螺科蜗牛共同的特征。因此，G。fluctuata是食草动物而不是捕食者。这一发现表明：1）原生动物最早出现于白垩纪中期; 2）白垩纪和侏罗纪的“原生动物”大多不是原生动物; 3）侏罗纪和白垩纪的“原生动物”并非通过贝壳钻探以软体动物为食。因此，看来原生动物的化石记录和它们的捕食痕迹是相互协调的。这一发现支持了原生动物捕食作用出现在白垩纪中期的假说。我们已经表明，有一些钻孔类似于不完整的钻孔由natidies。一个例子是来自日本和库页岛的白垩纪菊石中的帽贝家疤痕。帽贝的家痕是由领土和/或归巢物种通过化学溶解的方式产生的，并辅以辐射作用。然而，帽贝的家痕在形状和大小上不同于不完整的原生钻孔。在南达科他州重新发现的一只带有许多家庭疤痕和髌腹足类Limpets的胎盘角龙强烈表明，所谓的沧龙咬痕也是髌腹足类limpets的家庭疤痕。我们已经表明，海蜗牛的壳伸长是一个例子，反捕食适应natigins。虽然这项研究还在进行中，但很明显，细长壳体比圆形壳体具有更多的天然钻孔。

1. Based on anatomical research of a living fossil snail, Globularia fluctuata (Sowerby), this snail has a primitive nervous system and shares many features common to freshwater ampullariid snails. Also, G. fluctuata is grazer rather than predator. This discovery suggests that 1) naticids first appeared in mid-Cretaceous, 2) many Cretaceous and most of Jurassic "naticids" are not naticid, and 3) the Jurassic and Cretaceous did not feed on molluscs by shell drilling. Therefore, it appears that the fossil record of naticids and their predation traces are in harmony with each other. Our discovery supports a hypothesis that naticid predation appeared in mid-Cretaceous.2. We have shown that there are some boreholes similar to the incomplete drillholes by naticids. One example is the limpet home scars in the Cretaceous ammonites from Japan and Sakhaliin. Limpet home scars are produced by territorial and/or homing species by, means of Chemical dissolution, assisted by radular action. However, limpet home scars differ from the incomplete naticid drillholes in shape and size. Rediscovery of a Placenticeras meeki from South Dakota with many home scars and patellogastropod Limpets strongly suggests that the so-called mosasaur bite-marks are also home scars of patellogastropod limpets.3. We have shown that shell-elongation of marine snails is an example of anti-predatory adaptation agains naticids. Although this study is in progress, it is evident that elongate shell has more naticid drillholes than round ones.