Multiple evolutionary origins and losses of tooth complexity in
squamates.

Abstract

Teeth act as tools for acquiring and processing food, thus holding a
prominent role in vertebrate evolution. In mammals, dental-dietary
adaptations rely on tooth complexity variations controlled by cusp
number and pattern. Complexity increase through cusp addition has
dominated the diversification of mammals. However, studies of Mammalia
alone cannot reveal patterns of tooth complexity conserved throughout
vertebrate evolution. Here, we use morphometric and phylogenetic
comparative methods across fossil and extant squamates to show they
also repeatedly evolved increasingly complex teeth, but with more
flexibility than mammals. Since the Late Jurassic, multiple-cusped
teeth evolved over 20 times independently from a single-cusped common
ancestor. Squamates frequently lost cusps and evolved varied
multiple-cusped morphologies at heterogeneous rates. Tooth complexity
evolved in correlation with changes in plant consumption, resulting in
several major increases in speciation. Complex teeth played a critical
role in vertebrate evolution outside Mammalia, with squamates
exemplifying a more labile system of dental-dietary evolution.

Open access:
https://www.nature.com/articles/s41467-021-26285-w