Archaeornithes
plural noun
Ar·chae·or·ni·thes
| \ -ˈȯrnəˌthēz, -ˌȯrˈnī(ˌ)thēz\
Definition of Archaeornithes
: a subclass of Aves comprising the earliest and most primitive of fossil birds, retaining distinctive reptilian characters, and including the two genera Archaeornis and Archaeopteryx
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