Aerosteon

Aerosteon ("air bone") is a theropod dinosaur that lived in the Late Cretaceous of Argentina.

Description
Aerosteon was a medium-sized theropod, measuring about 9 meters in length. Its skeleton is incomplete, but the fusion of the bones indicate that this individual was not fully grown.

Some of the dinosaur's recovered bones contain air sacs, similar to the respiratory system of modern-day birds.

Classification and Discovery
Aerosteon is part of the family Neovenatoridae, which was a group of allosauroids that survived to the Cretaceous.

It was first described by Paul Sereno and others in 2008 on the online journal PLoS ONE. At the time, however, the International Zoological Code of Nomenclature did not recognize or validate names that were published online without an additional print copy. Thus, Aerosteon did not become a valid name until 2009.