> Finally, he showed me a photograph of a fossil jawbone; it belonged to the mammal he’d found in the burrow. “This is the jaw of Dougie,” he said. The bone was big for a Cretaceous mammal—three inches long—and almost complete, with a tooth
The mammal mentioned in the article was a marsupial, so not in our ancestral line. Marsupials have split from the eutherians (to which we belong) long before the C-T boundary. At C-T there were already early primates, which is our closer family.
A fascinating story about this is in Baxter's "Evolution" book which starts with a little primate at the CT boundary and traces the history of the family to modern humans.
7 cm jawbone. Some rat, that.