|Bite traces on Late Cretaceous dinosaur bones showing
serrated marks. From Jacobsen and Bromley (2009).
|Majungatholus tooth showing denticles and bite traces
showing denticle marks. From Rogers et al. (2003).
|Multituberculate gnaw traces on several Late
Cretaceous bones. From Longrich and
|Azhdarchid pterosaur long bone with tooth embedded (right side, bottom of the bone). Image by Liz Martin.|
|Close up of pterosaur bone with tooth emedded and bite traces visible. Image by Liz Martin|
The nature of the bite can also tell us about the nature of the animal making the traces. Most bite traces found in the fossil record are typical of scavenging. They show no evidence of healing, and are often found in areas that wouldn’t typically be covered in bites if it were something like live inter or intra-specific competition such as the ends of bones. However, there are also bite traces in the fossil record that show evidence of healing. A tyrannosaur (Daspletosaurus) shows evidence of several healed bites on its skull, leading the authors to believe this was some kind of intra-specific competition with other Daspletosaurus (Hone and Tanke 2015).
|Examples of dermestid mandible marks on
Jurassic Camptosaurus bones. From Britt
et al. (2008).
Of course predation traces are not restricted to vertebrates. They are commonly found on things like ammonites, which were often predated on by mosasaurs in the Cretaceous oceans. And of course predation traces or scars are not limited to being caused by vertebrates. Many invertebrates are capable of scarring bones and shells. Dermestid beetles are well known today for decomposing flesh and cleaning of skeletons, but they can also leave traces on the bones, and have been found in dinosaur fossils. Molluscs are known for using their “thorny tongue” or radula to scrape away shells in order to get inside the shell at the animal living inside. These bore-holes are common in modern shells and frequently seen in the fossil record as well. Sometimes these borings are stopped partway through the shell, and considered “unsuccessful”, while they are often termed “successful” as the hole goes through the shell to the unsuspecting clam or oyster within.
In addition to predation traces, there are also several other kinds of marks that can be found on a specimen, including trample traces, transport marks (abrasion, etc.), and other kinds of breakage indicators. This leads to the field of taphonomy, which is basically everything that has happened to an animal from the time it dies to when it is discovered by a palaeontologist. These things tell us about the environment it lived in and aspects of its preservation, and is much to wide of a topic to discuss here. Maybe next time!
Determining the different marks or traces on fossil bones, where they came from, and what other animal may have caused them can be extremely difficult, despite the fact that these marks can be extremely common in the fossil record.
NOTE: Since posting this, Lothar Vallon has pointed out that there is a specific scientific definition for the use of marks vs. trace, in case anyone is wondering why I use trace in most places and mark in others. You can see his comment below!
Britt, BB, et al. 2008. A suite of dermestid beetle traces on dinosaur bone from the Upper Jurassic Morrison Formation, Wyoming, USA. Ichnos 15: 59-71.
Currie, PJ, and Jacobsen, AR. 1995. An azhdarchid pterosaur eaten by a velociraptorine theropod. Canadian Journal of Earth Sciences 32: 922-925.
Hone, DWE, and Tanke, DH. 2015. Pre- and postmortem tyrannosaurus bite marks on the remains of Daspletosaurus (Tyrannosaurinae: Theropoda) from Dinosaur Provincial Park, Alberta, Canada. PeerJ 3: e885.
Jacobsen, AR, and Bromley, RG. 2009. New ichnotaxa based on tooth impressions on dinosaur and whale bones. Geological Quarterly 53: 373-382.
Longrich, NR, and Ryan, MJ. 2010. Mammalian tooth marks on the bones of dinosaurs and other Late Cretaceous vertebrates. Palaeontology 53: 703-709.
Rogers, RR, et al. 2003. Cannibalism in the Madagascan dinosaur Majungatholus atopus. Nature 422: 515-518.