Extract the answer to the question from the following context. Question: What species significant to humans appeared during these eras? Context: Recent molecular phylogenetic studies suggest that most placental orders diverged about 100 to 85 million years ago and that modern families appeared in the period from the late Eocene through the Miocene. But paleontologists object that no placental fossils have been found from before the end of the Cretaceous. The earliest undisputed fossils of placentals come from the early Paleocene, after the extinction of the dinosaurs. In particular, scientists have recently identified an early Paleocene animal named Protungulatum donnae as one of the first placental mammals. The earliest known ancestor of primates is Archicebus achilles from around 55 million years ago. This tiny primate weighed 2030 grams (0.71.1 ounce) and could fit within a human palm.
Answer:
The earliest known ancestor of primates