Figure 1

Timetree of edentulous and enamelless amniote taxa for which genomic sequences are available (Ensembl, PreEnsembl, NCBI) with a mapping of inferred inactivating mutations (frameshifts, premature stop codons, splice site mutations) in three EMP genes to particular branches in the tree. Branches with inactivating mutations are marked by vertical bars (pink = ENAM [E], blue = AMBN [B], green = AMEL [A]). Extinct stem taxa with teeth (Odontochelys, Ichthyornis, Eomaia) are also shown. Mutations were mapped to branches by Fitch parsimony with delayed transformation optimization. Teeth with enamel, teeth without enamel, and edentulism are denoted with black, gray, and white-filled circles, respectively, at terminal and internal nodes. In combination with fossil evidence, dN/dS ratios and frameshift mutations in ENAM suggest that enamel was lost independently in the common ancestor of Pilosa (sloths and anteaters) and in multiple armadillo lineages, including Dasypus[2]. Remnants of AMBN and ENAM were not recovered from the Pelodiscus genome. References for divergence dates and fossil ages are provided in Methods.