Jordan Bestwick, PhD student

Resolving pterosaur dietary ecology using tooth microwear and biomechanics

Supervisors: Dr David Unwin (University of Leicester), Professor Mark Purnell (University of Leicester), Dr Richard Butler (University of Birmingham), Dr Donald Henderson (Royal Tyrell Museum).

Project Overview

Jordan Bestwick
Jordan Bestwick

Pterosaurs were an extremely morphologically diverse group of flying reptiles which lived between 220-65 million years ago (Ösi 2011). This diversity was most pronounced in the shapes and sizes of their skulls. Palaeontologists have often inferred pterosaur diets by simply comparing the shapes of their teeth with those of living organisms (Ösi 2011).  However, this approach is purely qualitative and assumes a direct link between form and function in morphological features (Robinson & Wilson 1998).

My project therefore aims to quantitatively infer the dietary ecology of pterosaurs. This will be achieved by examining wear patterns on teeth in the form of scratches and pits, with patterns below 0.5mm in size defined as microwear (Williams et al. 2009). These patterns are formed when animals process food, and from tooth-tooth occlusion. The ‘toughness’ of different food items (fish, insects, plants etc.) produces particular signals for the type(s) of food consumed. This method is part of a larger on-going research programme at Leicester. Tooth microwear analyses in the last decade have been applied to extinct organisms such as early mammaliaforms (Gill et al. 2014) and even dinosaurs (Williams et al. 2009). However microwear patterns observed from extinct organisms need to be validated using extant analogues. A great deal of care must therefore be taken in deducing and sourcing suitable analogues with known dietary information. Currently postulated pterosaur microwear analogues include piscivorous crocodilians, omnivorous lizards such as skinks and insectivorous bats (Ösi 2011).

Collecting microwear data from pterosaur fossils will involve taking rubber moulds of teeth from museum specimens in the UK (NHM, Oxford etc.), Europe (Berlin, Karlsruhe etc.) and beyond (USA, China etc.) and filling these moulds with resin to create a replica of the tooth. The replica will then be subject to Scanning Electron Microscopy (SEM) to obtain a 3D image of the tooth, including any microwear present on its surface (Williams et al. 2009).

There is also scope to validate the microwear results with biomechanics using 3D mathematical slicing of their complete skulls to create a digital model (Henderson 2010). If the microwear patterns suggest a potential diet for a pterosaur species, the digital models can deduce the force needed to physically process the food item during feeding and whether the skull could handle them (Henderson 2010). This interdisciplinary approach allows more representative conclusions to be drawn on pterosaur dietary ecology, which can subsequently be applied to numerous other extant and extinct taxa (Hutchinson 2012).

Research Questions

  • Do pterosaurs with currently postulated different diets quantitatively show differences in microwear patterns?
  • Do microwear patterns vary depending on the side of the tooth sampled (labial vs. lingual, proximal vs. distal)?
  • Do microwear patterns vary on the position of the jaw (proximal-distal) in specimens with fully preserved jaws?
  • Do pterosaurs with specimens from their entire life-cycle show ontogenetic changes in microwear patterns?
  • Do different pterosaurs from the same locality show differences in microwear patterns?
  • Do the forces generated by the digital skulls agree with diets suggested by microwear patterns of corresponding pterosaur species?

References

  • Gill PG, Purnell MA, Crumpton N, Brown KR, Gosling NJ, Stampanoni M & Rayfield EJ. (2014) Dietary specilizations and diversity in feeding ecology of the earliest stem mammals. Nature, 512: 303-305.
  • Henderson D. (2010) Pterosaur body mass estimates from three-dimensional mathematical slicing. Journal of Vertebrate Paleontology, 30: 768-785.
  • Hutchinson JR. (2012) On the inference of function from structure using biomechanical structure using biomechanical modelling and simulation of extinct organisms. Biology Letters, 8: 115-118.
  • Ösi A. (2011) Feeding-related characters in basal pterosaurs: implications for mechanism, dental function and diet. Lethaia, 44: 136-152.
  • Robinson BW & Wilson DS. (1998) Optimal Foraging, Specialization, and a Solution to Liem’s Paradox. The American Naturalist, 151: 223-235.
  • Williams VS, Barrett PM & Purnell MA. (2009) Quantitative analysis of dental microwear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding. Proceedings of the National Academy of Sciences of the United States of America, 106: 11194-11199.

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