In the Permian period, for example (roughly 298 to 252 million years ago), we have evidence of animals such as Gorgonopsids - large, carnivorous, four-legged monsters with long, sabre-like fangs, strong rear legs, and a vaulted palate that allowed them to breathe when they grabbed their prey. The biggest was roughly the size of a large bear. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.