Given the following context:  A paleontologist named Zack takes his nephew Ricky and niece Jade on a fossil hunt. While alone, Ricky is met by a talking raven, who turns into an Alexornis named Alex. He tells him of a story set in the Cretaceous period 70 million years ago. Patchi is the smallest in a litter of Pachyrhinosaurus hatchlings, and is often bullied by his older brother Scowler. Their father Bulldust is the leader of the Pachyrhinosaurus herd. Alex, who is Patchi's mentor, tries to help Patchi impress a female Pachyrhinosaurus named Juniper, but her herd migrates south without him. Bulldust moves his herd south as well, but when they try to pass through a forest, they are forced to flee when a storm strikes and a fire erupts. Taking advantage of the chaos, a pack of Gorgosaurus attacks the scattered herd. They kill the rest of Patchi and Scowler's family while their leader Gorgon fights and kills Bulldust. Afterwards, Patchi's herd (now led by Bulldust's rival Major) combines with Juniper's as they continue their migration. There, Gorgon's pack attacks them again. In the ensuing chaos, Patchi, Scowler, and Juniper fall into a river and are swept downstream to the ocean, with Alex following them from above. At a beach, Scowler follows a herd of Edmontosaurus to find food, callously leaving Patchi and Juniper behind. The two make their way through a forest and eventually are able to find their herd and Scowler.  answer the following question:  Who is Bulldust the father of?
Patchi