Third upper molar enlargement in sigmodontine rodents (Cricetidae): morphological disparity and evolutionary convergence

Abstract

We studied the enlargement of the upper third molar (M3), with respect to the upper second molar in sigmodontine rodents, the largest subfamily of living cricetids. M3 is enlarged in extant and extinct members of at least six tribes (Andinomyini, Euneomyini, Oryzomyini, Phyllotini, Reithrodontini and Sigmodontini), all of them also sharing hypsodonty, planate crowns and overall dental simplification in the context of Sigmodontinae. Enlargement is expressed in four ways, including simplification or modest complication of occlusal design on a single plane. M3 enlargement in sigmodontines is primarily associated with increasing herbivory rather than strictly with phylogeny, and thus presents a classic example of evolutionary convergence.

Pliocene sigmodontine rodents (Mammalia: Cricetidae) in northernmost South America: test of biogeographic hypotheses and revised evolutionary scenarios

“…The datasets supporting this article (electronic supplementary material, S1, figures S1–S3) have been uploaded and are available from the Dryad Digital Repository: [141].…”

Figure 11: Main cranial traits differentiating species of Pattonimus gen. nov.: Pattonimus ecominga sp. nov. (top; MECN 5928, holotype) vs Pattonimus musseri sp. nov.

“…Hypsodonty in sigmodontines is usually linked with planar occlusal surfaces and simplification (see Ronez et al, 2020a, and the references cited therein). The latter process constituted one of the main elements in Hershkovitz (1962) understanding about molar sigmodontine evolution which involved, almost axiomatically, the evolutionary transition from complex (pentalophodont) to secondarily simplified (tetralophodont or derivates) molars.…”