Dodatak:Popis gmazova, O
Oe
uredi- Oedodera
- Oedura
Og
uredi- Ogmodon
Ol
uredi- Oligodon
- Oligosoma
Om
uredi- Omanosaura
Omoadiphas Köhler, Wilson & Mccranie, 2001
uredi- Omoadiphas aurula Köhler, Mccranie & Wilson, 2001
- Omoadiphas cannula Mccranie & Cruz-díaz, 2010
- Omoadiphas texiguatensis Mccranie & Castaneda, 2004
Reptilia → Squamata → Colubridae
Oo
uredi- Oocatochus
Op
uredi- Opheodrys
- Ophidiocephalus
- Ophiodes
- Ophiomorus
- Ophiophagus
- Ophioscincus
- Ophisaurus
- Ophisops
- Ophryacus
- Opipeuter
†Opisthodontosaurus Reisz et al., 2015
uredi- †Opisthodontosaurus carrolli Reisz et al., 2015
- Opisthotropis
- Opluridae
- Oplurus
Or
uredi- Oreocalamus
- Oreocryptophis
- Oriocalotes
- Orlitia
Klada Ornithodira Gauthier 1986
uredi- Dinosauromorpha Benton 1985
- †Pterosauromorpha Padian 1997
Animalia → Chordata → Reptilia
- Orosaura
- Orraya
- Orthriophis
Os
uredi- Osteolaemus
Ot
uredi- Otocryptis
- Otosaurus
Ou
uredi- Ouroborus
Ov
uredi- Ovophis
Ox
uredi- Oxybelis
- Oxyrhabdium
- Oxyrhopus
- Oxyuranus microlepidotus (McCoy, 1879) [1] kopneni taipan
- Oxyuranus scutellatus (Peters, 1867) [1] obalni taipan
- Oxyuranus scutellatus canni Slater, 1956 [1]
- Oxyuranus scutellatus scutellatus (Peters, 1867) [1]
- Oxyuranus temporalis Doughty, Maryan, Donnellan & Hutchinson, 2007 [1]