Proavis

Not to be confused with Protoavis.
Hypothetical restoration of "one of the Pro-Aves", as shown at the British Museum by William Plane Pycraft in 1906 (here extracted from Pycraft 1910 book A History of Birds).

Proavis refers to a hypothetical extinct species or hypothetical extinct taxon and was coined in the early 20th century in an attempt to support and explain the hypothetical evolutionary steps and anatomical adaptations leading from non-avian theropod dinosaurs to birds. The term has also been used by defenders of the thecodontian origin of birds.