Passage Summary: Some people think T. rex was too slow to hunt and must have just eaten dead things. The author says that's a bad guess because the T. rex's food might have been even slower than the T. rex itself.

Conclusion: The claim that T. rex was too slow to be a hunter is a hasty inference.

Reasoning: Even if T. rex was slow, its prey might have been even slower, meaning it could still have been a successful hunter.

Analysis: The specific phrase in the question is the conclusion of an opposing argument that the author is trying to debunk. The author introduces this idea only to immediately attack it. In LSAT terms, this is a 'claim the argument is designed to refute.' Focus on the transition 'This, however, is an overly hasty inference,' which signals that the preceding sentence is the target of the author's criticism.