Early birds were extremely rare in both number and variety, so their chances of becoming fossils were very slim. For example, in the nearly 140 years since 1861, only six skeletons and one feather specimen of Archaeopteryx from the Late Jurassic period have been discovered.
So, what about bird fossils after Archaeopteryx? Fishbirds and Hesperornis were also discovered as early as the 19th century. They were birds from the Late Cretaceous. Moreover, since very few Late Cretaceous birds have been discovered worldwide so far, and most of their fossils are incomplete, they remain the best-preserved bird fossils in Late Cretaceous strata to this day.
Three Pagodas, Chinese Bird
Before the 1980s, early Cretaceous bird fossils were one of the most regrettable gaps in paleontological evolution. Prior to this, the scientific community knew almost nothing about how birds evolved from their ancestor Archaeopteryx, which lived 150 million years ago, to more advanced birds less than 100 million years ago. Even the occasional sporadic discoveries were merely individual feathers or very fragmented bone fossils. They only indicated the existence of some birds and contributed little to the study of early bird evolution. This stagnant situation continued until the early 1980s, when a very incomplete bird skeleton was discovered in Mongolia in 1982, causing great excitement among paleontologists. Subsequently, an incomplete hind limb bone fossil was discovered in Gansu, my country. Professor Hou Lianhai, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, named it Gansuornis and considered it the ancestor of all later waterbirds and shorebirds. Following this, scientists discovered some feather fossils and two relatively complete skeletons at different locations in Spain; unfortunately, none of these discoveries included a skull. However, these successive discoveries continued to fuel scientists' hopes for solving the problems of early Cretaceous bird evolution. And, perhaps no one could have predicted that all these discoveries were merely the prelude to even greater discoveries to come. A few years later, a series of complete, exquisite, and historically significant early Cretaceous bird fossils were discovered in western Liaoning Province, my country, sparking a revolution in the study of early bird evolution.
The first major discovery of bird fossils in western Liaoning, China, was the discovery of the Chinese bird at the Three Towers.
In Chaoyang County, Liaoning Province, there lived an extraordinary farmer with a unique passion for science, which led him to acquire considerable knowledge of paleontology and fossils. During his off-season, he traversed the mountains and rivers surrounding his hometown, collecting numerous fossils. One day in 1987, he unexpectedly discovered a remarkably well-preserved bird fossil. The fossil was found in Early Cretaceous strata, and based on pollen analysis of the strata, it was estimated to be approximately 130 million years old. Except for a few missing bones, such as the sternum, the cranial skeleton was remarkably well-preserved. After careful study by Rao Chenggang, a young paleontologist at the Beijing Museum of Natural History, and Sereno, a young dinosaur expert at the University of Chicago, the specimen was finally named *Sinornithosaurus tritatus*. "Sinornithosaurus" clearly signifies its discovery in China; "Tritatus" commemorates the area where the fossil was unearthed, as three ancient pagodas from the Liao and Jin dynasties had stood there for over a thousand years. Researchers at the time announced that *Sinornithosaurus tritatus* was the earliest known flying bird in the world.
