Even as far back as the
Paleocene Epoch, the fauna still does not look all that much different from present-day fauna. Looking at the largest animals, I find in the mid-Paleocene
Barylambda which was the size of a small horse, but with five-digit feet much like those of rats and opossums. BTW, opossums are sometimes called "living fossils", from their resembling late-Mesozoic mammals. Also in the mid-Paleocene, I find
Gastornis a bird that was roughly the size of a present-day ostrich, though with a much thicker neck and bigger head. A bit on the weird side, I must note.
But before the K-Pg mass extinction, the larger fauna looked very different. Here are some size champions from around that time.
Dinosaur size
Triceratops looked something like a rhinoceros, but was elephant-sized, had horns over its eyes, and a neck frill. It had a beak and back teeth.
Ankylosaurus had human height and a three times longer body. It had armor plates on its back, a long tail, and also a beak and back teeth.
Edmontosaurus was a very large hadrosaur, roughly elephant-sized, but with a tail about as long as the rest of its body. Its head was flattened at the front end, the duckbill feature. It had a beak and back teeth, continually growing new ones.
Titanosauria were sauropods, the largest land animals known to exist. They had elephant-like bodies, but long necks, small heads, and long tails. Their long necks were likely a way to avoid moving very much when eating. The animal could turn its neck from side to side, eating as it goes.
Tyrannosaurus - elephant-sized, but with conical teeth, bipedal, and with a long tail, was among the largest land predators that ever lived. Stephen Jay Gould recalled being very impressed by a mounted skeleton of one when he was a little boy.
There were plenty of smaller ones, but many of them had similar sorts of features.
Some of the smaller ones likely had feathers:
Feathered dinosaur -
List of non-avian dinosaur species preserved with evidence of feathers - most of the evidence is from theropods, the group that includes tyrannosaurs and birds. Not only small ones like
Archaeopteryx but also
Ornithomimus - roughly human-sized with a hip height of around 1 meter.