At https://phys.org/news/2021-10-cool-oasis-cretaceous-feathered-dinosaurs…. … dinosaur fossils have been popping up galore in parts of China in recent years. The Jehol Biota, in particular, in NE China, has proved to be a hot spot of feather dinosaurs – together with a wide array of Cretaceous flora and fauna. Paleontologists don't think feathers, which evolved during the Jurassic, were originally used to fly. That came later. Early examples are too small and stubby to support flight. Instead, like feathers on modern birds dinosaur feathers served other purposes. Such as insulation. Lead author, Laiming Zhang, a paleoclimatologist, estimated air temperatures at 125 million years ago using isotopes of carbonate minerals they found in the soils at the site. He found low spring time temperatures suggesting a cool climate. Mainstream consider temperatures during the Cretaceous, and the Jurassic, were warmer than in the modern world, which Zhang took into consideration. So how did he get around the oddity of a cool climate? We know the idea of a warmer climate comes mostly from the fact the poles supported trees and vegetation, and therefore probably wildlife in general, in the dinosaur era. The idea it was warmer globally is an extrapolation from that. Zhang, in order to get published, had to find a valid reason for the cool NE Chinese climate. He, therefore, looked at elevation – altitude at Jehol Biota. He came up with a figure of 3 to 4 km higher than it is today. To justify this position he points out that in the Early Cretaceous, NE China experienced dramatic tectonic changes – the Yanshanian Orogeny.
Biology also supported a cooler climate, the remains of plants adapted to a cool ecosystem. The same was true of insects. Zhang, therefore, proposed that dinosaurs in the region would have benefited from insulation in order to stay warm. The piece ends with a comment from an evolutionary paleobiologist from the University of Texas, Sarah Davis. She says that the preponderance of feathers in this part of China makes sense if there was a cooler climate. However, we may note the idea there was an elevation of 3 to 4 km is another question. Once again, it would be useful if mainstream did not rely on data from western Europe and North America, and explored temperatures in other parts of the world during the dinosaur era.