Quick impression of the "Air Bone" abelisaur, best known for having the best-preserved internal limb bone structures yet discovered in a large dinosaur... which revealed something about the non-maniraptoran and non-coelurosaurian dinos of Family Theropoda... They had the same bone structures as modern birds, with bubble structures implying they had a similar pulmonary system as well. While this may be just convergent evolution, it suggests that the theropod dinosaurs aren't just proto-birds, similar to how many early mammals were once classed as "proto-mammals" when the actual proto-mammals were far more reptilian... Dinosaurs, the long-thought "proto-birds", are probably just an earlier incarnation of Avian, with our simplistic human assumptions of what a "bird" is, based only upon the twittering little creatures of beak and fully-specialized feathery wings, getting in the way for so long. Logically, this should have been hit upon the moment molecular isotopes in the bone marrow of fossils could be analyzed... Even the most lumbering, huge, "non-avian" dinosaur species tested in this way show an isotope ratio far to the avian end, and far from the archosaurian ancestor. Archosaurs, which had some of the avian features but not all, amazing creatures that were partly bird-like (active metabolisms, three and four-chambered hearts, some lightened bones, etc.) and still largely reptilian, are the true proto-birds. ^^

So here is the big bird drawn with nib-tipped pens in india ink... Aerosteon was an abelisaur related to Carnotaurus and Krytops and Rugops, known largely from some leg bones and vertebra from the neck, back, and a few from the tail. Enough to tell what group of dinosaur it belongs to, its scale, and its general body shape. These remains, scattered as they are, must have been fresh enough to have so much of the delicate internal structures of the bones preserved but had obviously been scavenged on, as no trace of soft tissues remained. The likely story of these specimens is that an Aerosteon passed away and some other creatures, possibly other Aerosteon or abelisaur species, nibbled off the useful meat and destroyed the tendons holding the bones together closely, causing bits and pieces to scatter before some larger event (flooding, volcanic, or mudslide) quickly covered what was left and preserved it to this day. ^^

To commemorate the bird-dinosaur connection these fossils gifted us, I've recreated Aerosteon as a heavily feathered abelisaur of medium size, with fairly agile legs, short limbs useful only for displays and pushing up piles of vegetation for nesting structures, and many whiskery quills that arose from down feathers--mostly for show and for keeping parasites and insect blood-suckers away from the exposed skin of the face and the hard-to-reach back. He also looks like an old Kung-fu Master this way. XD