Thecodont tooth attachment and replacement in bolosaurid parareptiles: Author Interview with Adam Snyder

Today we published Thecodont tooth attachment and replacement in bolosaurid parareptiles

The study examines how Bolosaurids jaws were constructed revealing unusual patterns of tooth development and replacement. We spoke to Author Adam Snyder to find out more.

Can you tell us a bit about yourself?

Adam Snyder

This June I will have completed my undergraduate degree at the University of Toronto Mississauga campus. Majoring in Paleontology and Earth Science I was excited to undertake research alongside my coursework. Under the supervision of Dr. Robert Reisz in the Vertebrate Paleontology lab I was given access to amazing fossil material and a global network of experts that led to my first publication.

Can you briefly explain the research you published in PeerJ?

Bolosaurids have been primarily characterized by their dentition because superficially it’s quite odd. They show extreme heterodonty across the jaw, early signs of occlusion in the fossil record, and almost always a complete set of teeth (Usually fossil amniotes will have gaps in their teeth, so this record of complete sets is interesting).

Our study examined how their jaws were constructed. We showed how to differentiate tissues of the jaw by comparing computed tomography and histology. These techniques revealed that the roots of Bolosaurid teeth were much longer than their crowns, the classic definition of thecodonty. Examining the roots revealed that many of the specimens contained developing teeth below their functional counterparts. Through the scan data we could show the relationship between the functional tooth, developing tooth and the surrounding tissues. Each time there was a replacement tooth a hole formed through the jaw, in some cases exposing the developing tooth. This 1:1 relationship was very interesting as these holes seemed to close to strengthen the attachment of the new tooth.

The final piece to the puzzle was the holotype. This is the only Bolosaurid specimen with a tooth gap, providing insight into replacement. The CT data showed that each tooth behind this gap had a nearly complete developing tooth and every position before did not have a developing tooth. This means that the animal died midway through a replacement cycle. This is the key element to support a wave-based replacement model for early herbivores going back sixty years.

Figure 1: ROMVP 83327 Bolosaurus grandis right dentary fragment.
(A) Lingual, (B) labial, (C) inferior, and (D) superior view with histological cuts marked in red. (E) Transverse histological view of inferred tooth locus 10. (F) Transverse digital thin section of inferred tooth locus. (G) Labial tooth segmentation. (H) Labial segmented profile with the addition of alveolar bone. (I) Complete labial dentary segmented profile. (J) Sagittal histological view of inferred tooth loci 11 and 12. (K) Close up of enamel structure. (L) Sagittal digital thin section of inferred tooth loci 11 and 12. ab, alveolar bone; de, dentin; e, enamel; jb, jawbone; pc, pulp cavity. Scale bars are 2.5 mm except 100 µm in K.

Bolosaurid Jaw Animation

How was your publishing experience with us?

PeerJ was an excellent publisher to work with. Timely in their responses, whether it was general updates in the process or if I needed clarification at any stage. First publications are intimidating; however, their teams were helpful and supportive throughout. When it came to rebuttals, comments were organized neatly in a review pdf which was easy to work with. Our response letter was a ‘call and response’ of sorts, using different font styles to break up the speakers. I would definitely submit to this journal again.

Thanks for sharing your research story, Adam! You can read his full paper here.

You can find more PeerJ author interviews here. View related research in PeerJ’s Paleontology and Evolutionary Science section.