No remnants of nasolacrimal ducts in any Desmognathini salamanders indicates loss early in their evolutionary history
Previous studies demonstrated that nasolacrimal ducts were present in the ancestral plethodontid lineage. Two lineages within Plethodontidae contain individuals that do not possess nasolacrimal ducts: Desmognathus and Eurycea. Earlier works examined only two species of Desmognathus, D. fuscus and D. monticola. We obtained every Desmognathini (Phaeognathus + Desmognathus) species possible from novel collections and museum collections and assessed presence or absence of nasolacrimal ducts using contrast-enhanced computed tomography and routine histological procedures. The goal was to test the hypothesis that nasolacrimal ducts were lost on the evolutionary branch leading to Desmognathus. We rejected our hypothesis by finding that nasolacrimal ducts were absent in all Desmognathus that we examined and Phaeognathus hubrichti; thus, we recovered the absence of nasolacrimal ducts on the evolutionary branch leading to Desmognathini.