Evolutionary history of naticid shell-drilling predation

1.基于活体蜗牛化石的解剖学研究，这种蜗牛具有原始的神经系统，并具有许多淡水壶腹螺类的共同特征。此外，波动天牛是食草动物，而不是捕食者。这一发现表明：1)本生动物最早出现在白垩纪中期，2)许多白垩纪和大部分侏罗纪的“本生动物”不是本生的，3)侏罗纪和白垩纪并不是通过贝壳钻探来捕食软体动物。因此，原生动物的化石记录与它们的捕食痕迹似乎是一致的。我们的发现支持了一种假说，即白垩纪中期出现了本地化捕食。我们已经证明，有一些类似于本土化不完全钻孔的钻孔。一个例子是来自日本和库页岛的白垩纪菊石中的帽贝家庭伤痕。帽贝的家疤痕是由领地物种和/或归宿物种通过化学溶解的方式产生的，并辅以辐射作用。然而，帽状房屋的伤痕在形状和大小上与不完整的本地人的钻孔不同。在南达科他州重新发现了一只有许多家庭疤痕和膝天足类帽状物的Placeneera meeki，这有力地表明，所谓的马萨龙咬痕也是膝天足类边缘的家乡疤痕。我们已经证明，海洋蜗牛的壳延长是对原生生物进行反捕食适应的一个例子。虽然这项研究正在进行中，但很明显，细长的贝壳比圆形的贝壳有更多的本土化钻孔。

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.