In the Northeast of China, near the DPRK border, fossils have been discovered that have revolutionized the way we see dinosaurs. The tephra layers of the Yixian formation are full of remarkably well-preserved dinosaurs, often retaining details that are usually lost.

This is how we know that Yutyrannus huali (the big boi in the center of the pic), an early, already large tyrannosaurid clocking in at a length of 9 meters, had feathers. Or that Psittacosaurus (shown in the lower right) had quills or bristles on its tail. In many cases, we can even determine the coloration of these animals, which is how we found out that the tiny Sinosauropteryx had a ringed tail like a raccoon. Given that snowfalls were common in the winters of the Jehol biota, these feathers certainly served them well to keep warm in that climate.

These animals shared their home with a wide variety of different species - from fish-eating miniature ankylosaur Liaoningosaurus to the feathered vegan theropod Beipiaosaurus, from giant sauropods like Dongbeititan dongi to little hunters like Microraptor that was able to glide from tree to tree on his four wings. And Yixian had a lot of trees back then, conifers and pines and araucarias that formed lush forests with an undergrowth of ferns. In these forests lay cristal-clear lakes, their mineral-rich waters nurturing horsetails and gingkos on their shorelines. They swarmed with fish like Lycoptera and small aquatic reptiles looking like miniature plesiosaurs. Overhead flew early birds like Confuciusornis or Anchiornis alongside pterosaurs.

Regular volcanic activity was a threat to all of these animals, covering the forests in thick ash blankets that are the reason why so many fossils remain from that era. Their legacy lived on, though. Yixian was the starting point for the evolution of many dinosaur species that spread all over Asia and North America, like the ceratopsians, the tyrannosaurids, the therizinosaurs or the oviraptorians.