Beyond Domestication: Occurrence of Levator Anguli Oculi Medialis and Retractor Anguli Oculi Lateralis in Four Neotropical Canid Species.

Abstract

The facial mimetic muscles levator anguli oculi medialis (LAOM) and retractor anguli oculi lateralis (RAOL) have been associated with expressive eye movements in canids and proposed as products of domestication. We investigated their occurrence in four Neotropical species (Lycalopex gymnocercus, Lycalopex vetulus, Cerdocyon thous and Chrysocyon brachyurus). Twelve adult specimens were dissected, and both muscles were consistently identified in all taxa, with conserved architecture. These findings support the interpretation that LAOM and RAOL are not exclusive to domestic dogs and may represent a broadly conserved trait across Canidae.