This was a giant mammal that coexisted with dinosaurs. I had always thought that mammals appeared during the age of dinosaurs, but they were all tiny mouse-sized mammals.
You can see in this graph when their ancestors an our ancestor split. https://en.wikipedia.org/wiki/Evolution_of_mammals#Therapsid... It's the third branching in this graph.
For comparison, see the graph in the same page https://en.wikipedia.org/wiki/Evolution_of_mammals#The_ances... . Here is the split between reptiles/dinosaurs/birds and the ancestors of mammals in the second branching. (You can "glue" the other graphic in the lowest branch of this graphic, but I'm not sure if they have a comparable level of detail.)
(On the Giant Frying: http://uahost.uantwerpen.be/funmorph/raoul/macroevolutie/rob... )