1. Primitive reptile-like fossil birds of the Jurassic or early Cretaceous
   - Archaeornithes

Type of: class

Part of: Aves, class Aves

• oppressively
• oppressiveness
• oppressor
• opprobrious
• opprobriously
• opprobrium
• oppugn
• oppugnant
• Ops
• Opsanus tau
• opsin
• opsonin
• opsonisation
• opsonise
• opsonization
• opsonize
• opt
• opt out
• optative
• optative mood
• Optez
• opthalmic
• optic
• optic axis
• optic chiasm