"Opposite birds (enantiornithes) are the most primitive birds in the ecosystem, still retaining a full set of teeth and clawed wings. Avisaurus (meaning Bird Saurian) is one of the last of this group and the largest bird at Hell Creek."
―Saurian: A Field Guide to Hell Creek
Avisaurus was an extinct genus of avialan, known from the Hell Creek Formation. It was an enantiornithean, a group of extinct avialans that were abundant in the Cretaceous, distinguished for having mostly beakless toothed jaws and clawed wings, as well as lacking a defined feathered tal fan, but still remaining the typical shape of a modern flying bird. Avisaurus was probably a carnivore and a aerial predator, hunting for small birds, reptiles and mammals, like a small falcon or hawk, although it was probably more opportunistic, hunting for small invertebrates and also eating some plant material.
In Saurian[]
Avisaurus wingspan
Avisaurus has been expressed as a future appearance in the game. It will act as a flying animal in-game, and will be an AI.