O. canna, [316];

O. livingstonii, [316]

Ornithodelphia, [106]

Ornithorhynchidae, [112]

Ornithorhynchus, [112];

O. anatinus, [112];

shoulder girdle of, [34];

skeleton of, [114]

Orohippus, [248]

Orycteropodidae, [187]