Results of Wilcoxon tests for OEI vs NALMA.

<p>Results of Wilcoxon tests for OEI vs NALMA.</p

Occlusal Enamel Complexity in Middle Miocene to Holocene Equids (Equidae: Perissodactyla) of North America

<div><p>Four groups of equids, “Anchitheriinae,” Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, but only the Equini remains after 16 Myr of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes influencing the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. We investigated Occlusal Enamel Index, a quantitative method for the analysis of the complexity of occlusal patterns. We used analyses of variance and an analysis of co-variance to test whether equid teeth increase resistive cutting area for food processing during mastication, as expressed in occlusal enamel complexity, in response to increased abrasion in their diet. Results suggest that occlusal enamel complexity was influenced by climate, phylogeny, and tooth position through time. Occlusal enamel complexity in middle Miocene to Modern horses increased as the animals experienced increased tooth abrasion and a cooling climate.</p></div

Results of Wilcoxon test for OEI vs Tribe within each NALMA.

<p>Results of Wilcoxon test for OEI vs Tribe within each NALMA.</p

Representative teeth of each tribal-level group in this study.

<p>(A) Hipparionini, (B) Equini, (C) “Merychippini,” and (D) “Anchitheriini.” Each tribe has a distinct enamel pattern; the patterns decrease in complexity from A to D.</p

Results of Wilcoxon test for OEI vs Tribe.

<p>Results of Wilcoxon test for OEI vs Tribe.</p

Results of Tooth Position ANOVA and Tukey-Kramer Test.

<p>Results of Tooth Position ANOVA and Tukey-Kramer Test.</p

Results of ANOVAs and Tukey-Kramer Tests for OEI vs Tribe within each NALMA.

<p>Results of ANOVAs and Tukey-Kramer Tests for OEI vs Tribe within each NALMA.</p

Results of Tooth Position Wilcoxon Test.

<p>Results of Tooth Position Wilcoxon Test.</p

Results of ANOVA and Tukey-Kramer Test for OEI vs Tribe.

<p>Results of ANOVA and Tukey-Kramer Test for OEI vs Tribe.</p

Results of ANOVAs and Tukey-Kramer Tests for OEI vs NALMA.

<p>Results of ANOVAs and Tukey-Kramer Tests for OEI vs NALMA.</p