In the hypothetical scenario in which there was something to find in Antarctica in the first place, given the thorough scraping the continent has gotten for 20+ megayears by kilometers-deep glaciers you can't expect to find much at all. The areas not covered by glaciers are generally mountains which erode - their modern exposed surfaces would have been quite deep underground at the time.

The sorts of things you could actually expect to find would be more along the lines of missing coal seams, long rods of long-ago-oxidized steel poking vertically through multiple strata into areas that would have held petroleum deposits at the time, really deep coal seams turned to ash in situ by underground gasification, hydrothermal features that concentrate copper and silver ore capped by weird craters that obliterate where the highest concentrations would have been with a big pile of copper-depleted gravel nearby. Perhaps odd isotope ratios in a very narrow sediment band if nuclear reactions were ever explored. The ecological effects you would expect on the continent are kind of overshadowed in the ocean sediment record by the worldwide climate event that the PETM represents (6C temperature spike, deep ocean hypoxia, phytoplankton death and repopulation).

It's worth noting that there are probably particular clades that are predisposed to being smart. There's a fascinating book out by Dr. Herculano-Houzel ("The Human Advantage") detailing recent work over the last decade examining brain structure across the mammals. She and her group found something fascinating: neural scaling laws differ from clade to clade. Mammals in general have a neural scaling law that if you make a brain 10x as large, it only has 4x as many neurons as the neurons on average increase in volume (partially due to longer connecting fibers). Primates break this though - all primate neurons are about the same size, which is remarkably small, the same size as that of a mammal that's like 10 grams in mass. A large primate brain is MUCH more powerful than a generic mammal brain of the same mass. Their recent work since that book came out indicates that birds also break that scaling law and have marvelously efficient brains - all bird neurons are approximately the same size like the primates, but what's more that size is 6x as small as those of primates. It is an interesting question if this would also have applied to dinosaurs, their close relatives who nonetheless were not under crazy selective pressure for low weight.