Omosaurus = Stegosaurus, [425]

Omosternum of Anura, [25];

taxonomic value, [141]

Onychodactylus, [96];

O. japonicus, [109]

Operculum of gills, [44]

Ophiderpeton, [81]

Ophidia, [491], [581] f.

Ophiophagus, [632]

Ophiops, [551]