Introduction: In vertebrates, a corneal endothelium is essential for the maintenance of corneal transparency in a variety of environments, including aerial, terrestrial and aquatic. Knowledge of the surface structure of the corneal endothelium may assist our understanding of this unique tissue and its evolutionary development. Except for humans and some mammals, there have been few studies of other vertebrates, particularly the unique Australian species.

Methods: The field emission scanning electron microscope was used to study the corneal endothelium in representatives of four vertebrate classes: Teleostei (five species), Reptilia (two species), Aves (four species) and Mammalia (three species), including Marsupialia (two species). Endothelial cell densities were calculated from micrographs using computer‐based image analysis.

Results: The cell densities varied considerably from 1,900 ± 197 cells per mm² for the bream to 11,734 ± 1,687 cells per mm² for the emu. Most of the corneal endothelia were similar to those reported for mammals. However, in some species such as the koala, the pattern was irregular. Some endothelial cells in birds possessed cilia.