Aucasaurus is a genus of medium-sized theropod dinosaur from Argentina that lived during the Santonian - Campanian stage of the Anacleto Formation. It was smaller than the related Carnotaurus, although more derived in some ways, such as its extremely reduced arms and almost total lack of fingers. The type skeleton is complete to the thirteenth caudal vertebra, and is relatively well understood, making it the most complete abelisaurid yet described. However, the skull is damaged, causing some paleontologists to speculate that it was involved in a fight prior to death.
A pair of Aucasaurus are first encountered hunting a Saltasaurus. The female appears a few months later, this time with a flock of hatchlings, one of which is named Dragonfly after his love of chasing them. When the father returns, he is greeted with hostility until he soothes his mate with his colorful throat. The pair go on a hunt the next day, attacking a Saltasaurus herd. They attempt to take an adult until Dragonfly finds where most of the young are hiding, calling over his parents who then eat all of the young they find. As they are leaving, Dragonfly happens upon where Alpha and two other Saltasaur young are hiding, but gets distracted by a grasshopper before he can alert his parents.
Years later the family is once again seen hunting the Saltasaurus herd, this time with the young having grown up. They stalk the herd until a female is caught on softer soil, causing her to fall and be unable to get up as the pack eats her alive. While eating Dragonfly pushes his sister and is scolded by his father for this. Once the pack lies down to rest, Dragonfly decides it's time for him to leave and abandons his family.
While wandering he once again comes across Alpha, but leaves her be for now, then finds a lone female Aucasaurus. After a confrontation he is able to win her over and become her mate. They then begin following the Saltasaur herd, but never being shown to successfully kill any. At one point they find a dead one and attempt to scavenge it, only to be chased off by a nearby pair of Carcharodontosaurs. They eventually find a wounded Alpha, separated from the herd. They attack her, but the female is briefly knocked out and Dragonfly killed. The female then attempts to wake her mate, crying in anguish as Alpha leaves.
- It is unlikely that the adult Aucasaurus would be satisfied with eating only baby Saltasaurus as it wouldn't be filling enough. Nor would they bring their own young to hunt while as toddlers.
- The colors used to distinguish the males and female Aucasaurus are very similar to the colors between Carcharodontosaurs, and vice versa.
- The Aucasaurs depicted in the show possess a speculative Gular Pouch, in which it uses to attract mates, as demonstrated by Dragonfly. Two modern day birds that possess these throat pouches are Frigatebirds and Sage Grouse.