Limenavis

Limenavis is a prehistoric bird genus from the Late Cretaceous. It lived about 70 million years ago, around the Campanian-Maastrichtian boundary. Known from several broken bones, the remains of the only known species Limenavis patagonica were found in rocks of the "lower member" of the Allen Formation at Salitral Moreno, 20 km south of General Roca, Río Negro (Argentina).

Of all the prehistoric birds known to date, this species is among those closest to the common ancestor of all living birds. Its generic name pays tribute to this fact: Limenavis, meaning "bird of the threshold" or "limit-bird", is derived from Latin limen ("threshold") + avis ("bird"). The specific name patagonica refers to the specimen's Patagonian provenance.

The relationship of Limenavis to other Mesozoic birds has been difficult to determine. Analyses published in 2001 and 2002 by Julia Clarke and Luis Chiappe found Limenavis to be a carinate bird more advanced than Ichthyornis but not a member of the modern bird group Neornithes. A 2013 analysis by O'Connor and colleagues found it to be slightly more primitive than Ichthyornis.

It has been suggested that some features link it with paleognath birds, perhaps related to the ancestors of tinamous or rheas. Though such birds must have existed by that time already, and most likely at least tinamou ancestors (basal Tinamiformes) did live in South America by the Late Cretaceous, Tinamous proper (Tinamidae) are only known with certainty since the Miocene.