The remains document the Cambrian explosion, a rapid flourishing of life-forms, and include many organisms never seen before — even at the most famous Cambrian fossil site, Canada’s Burgess ShaleCarolyn Gramling, “Science News’ favorite fossils of 2019” at Science News
So even more fossils just popped into existence, just like that. No wonder even Darwin had doubts.
From 290 million to 280 million years ago:
For such an ancient critter, O. pabsti — one of the earliest amniotes, a group that includes reptiles and mammals — had a surprisingly efficient gaitCarolyn Gramling, “Science News’ favorite fossils of 2019” at Science News
So the long, long Darwinian period when the creature just stumbled uncertainly around may have been short or may not have existed? Then what was the mechanism of gait development?
See It takes a smart robot to mimic a reptile.
and a third:
From 99 million years ago:
A chunk of amber containing the right leg and foot of a sparrow-sized bird (illustrated) revealed a bizarrely long digit.Carolyn Gramling, “Science News’ favorite fossils of 2019” at Science News
Possibly the long toe was used for prying things out of holes, like a nut pick. But a more complete fossil record reveals many complexities that challenge simplistic claims and easy explanations of how evolution happens. As research continues apace, any given such theory might be challenged by something just around the corner.
See also: At The Scientist: “Junk RNA” is top science news in 2019 A “completely unknown biology,” says a researcher. “There really is no framework in biology as we know it today that would explain how RNA and glycans could ever be in the same place at the same time”