As the dentist’s drill vibrated my teeth last week—and before being interrupted by the nurse being stung by a wasp (in Scotland in the middle of November)—I was thinking of a paper I had been reading on the teeth of snakes and the role of a particular component, plicidentine.
Plicidentine—a folded form of dentine—was found in the teeth of the snakes examined. Potentially it is present in all species of snake. Previously in extant reptiles it had only been found with any degree of certainty in some ‘varanoid’ lizards. The authors of the paper realised that the direction of the folding could explain how tubular fangs of venomous snakes have developed independently three times during the course of evolution. Tubular fangs are viewed developmentally as fully closed grooved fangs. The orientation of the folds in the plicidentine makes it easy to envisage that any one of the folds in non-venomous ancestors could have developed as a grooved fang involved in the delivery of venom.
A previous suggestion that plicidentine increases resistance to bending or compression during biting was examined in but biomechanical experiments provided no support for that view. Instead the authors suggest that plicidentine acts to improve the attachment of the long but shallowly rooted teeth to the underlying bone by providing an increased surface area. Since the teeth of ‘varanoid’ lizards are also relatively long and shallowly attached, the presence of plicidentine in these lizards as well as in snakes would fit the explanation proposed.
Palci A, LeBlanc ARH, Panagiotopoulou O, Cleuren SGC, Mehari Abraha H, Hutchinson MN, Evans AR, Caldwell MW, Lee MSY. 2021 Plicidentine and the repeated origins of snake venom fangs. Proceedings of the Royal Society B 288. 20211391. https://doi.org/10.1098/rspb.2021.1391
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