Who did it? Bite marks in Jurassic and Cretaceous ammonites

Adiël A Klompmaker (USA) Ammonites are among some of the best fossils to collect. They are relatively easy to find, for example, in the Lower Jurassic Posidonia Shale in Germany and the Jurassic sediments of Dorset in the south of England. The larger, well-preserved ones will always be sought after and, if of sufficiently high quality, may even be displayed in museum exhibitions. However, while these nicely-preserved, complete ammonites are ideal for identifying species, they often do not say much about the life history and, more specifically, the death of the ammonite itself. On the other hand, studying the sub-lethal or lethal damage to the fossil shell certainly does. This article is about a relatively newly discovered type of bite mark. It is found on Jurassic and Cretaceous ammonites, might have occurred worldwide, is easy to recognise and is also fairly common. Ventral damage When I was browsing through the ammonite collections of several Dutch museums (including, Naturalis and Oertijdmuseum De Groene Poort) and the Geologisch-Paläontologisch Institut der Universität Münster in Germany, it became apparent to me that there were many specimens with damage to the outer whorl, on the back side of an ammonite (the ventral side) in its living position. This damage was not only visible on the ventral side, but could also be seen on both lateral sides, if preservation permitted. Fig. 1. Measurements relative to the aperture (A) and relative to the last septum (B). After Klompmaker et al. (2009). When viewed from the lateral side, … Read More

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