Dibley, G.E. (1911)
On the teeth of Ptychodus and their distribution in the English Chalk. Quarterly Journal of the Geological Society of London, 67, 263–277
DOI: 10.1144/GSL.JGS.1911.067.01-04.10
Guinot, G. & Condamine, F.L. (2023)
Global impact and selectivity of the Cretaceous-Paleogene mass extinction among sharks, skates, and rays. Science, 379, 802–806
DOI: 10.1126/science.abn2080