Tracing the First Fliers: What China’s New Jurassic Bird Fossil Tells Us About Evolution

Today, we’ll talk about the recent discovery in Fujian, China of the oldest confirmed Jurassic bird fossil that pushes the timeline of avian evolution further back by 20 million years, providing new insights into the transition from dinosaurs to birds.

Transcript

Tracing the First Fliers: What China’s New Jurassic Bird Fossil Tells Us About Evolution

Today, we’ll talk about the recent discovery in Fujian, China of the oldest confirmed Jurassic bird fossil that pushes the timeline of avian evolution further back by 20 million years, providing new insights into the transition from dinosaurs to birds.

This new discovery from the Jurassic period is called Baminornis zhenghensis, and to give us an idea of what it would have looked like while alive, ecological scientists have provided an illustration. About the size of a modern-day cockatoo, it is perched on a lakeside tree gripping the trunk with powerful claws. Its head is raised alertly and displays a feathered crest. Its body is covered in blue-green and orange-red feathers and bears a close resemblance to modern birds.

In February of this year, a joint research team from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences and the Fujian Institute of Geological Survey published a paper in the journal Nature. Two years ago, researchers discovered the world’s oldest known bird fossil in the Daxi Basin of Zhenghe County, Fujian Province. After restoration and analysis, the team determined that the fossil belonged to a bird species from approximately 148 million to 150 million years ago. They named it the Baminornis zhenghensis.

The discovery of the Baminornis zhenghensis confirms that the body structure of modern birds had already emerged by the Late Jurassic period. Through analysis, the research team pushed the origin of birds back to the Late Middle Jurassic, approximately 172 million to 164 million years ago – nearly 20 million years earlier than previously believed. Wang Min, a researcher at the Institute of Vertebrate Paleontology and Paleoanthropology and the author of the study, told The Context: “Through the discovery of the Baminornis zhenghensis, we realized that our current understanding of bird origins may be just the tip of the iceberg.”

Since 2021, the two institutes have been jointly conducting paleontological investigations across various basins in Fujian. In the second half of 2022, the team moved northward to Zhenghe County, where they identified a Late Jurassic basin in Yangyuan Township. In October of that year, they discovered Fujian’s first dinosaur skeletal fossil. After restoration and analysis, this new species was ultimately classified as a member of the Avialae clade and named Fujianvenator prodigiosus. Wang Min remarked, “The discovery of Fujianvenator made us realize the great potential of this site, as we subsequently found additional turtle, tortoise, and choristodere fossils.”

The team conducts fixed field excavations twice each year – one from late February to early May and another from late September to early December. From 2021 to 2023, the team maintained this schedule for more than 300 days, pausing their fieldwork only on rainy days.

On November 11, 2023, early winter weather had brought a chill to Fujian. Wang Min noticed that it had rained the night before, and since rainy weather makes conditions unfavorable for fieldwork, the team was considering not venturing up the slippery mountain roads. However, around midday, Wang Min noticed that the sky was gradually clearing. A cold wind swept through, quickly drying the rainwater on the ground. With conditions improving, the team decided to head up to the quarry on the mountaintop. The quarry was about three to four meters deep, and just as they had done for the past 300 days, they carefully lifted every potentially fossil-bearing rock from the pit, split them open with geological hammers, and meticulously examined them for traces of fossils.

This time, an astonishing discovery came. A technician from the Fujian Geological Survey Institute found a rock about 15 centimeters long and 10 centimeters wide, with exposed skeletal remains. He handed it to Wang Min, and though the rock was small, Wang quickly noticed two distinct bones – one scapula and one coracoid. His initial assessment was that it was likely a bird fossil. Without hesitation, Wang took a photo and sent it to his PhD advisor, Zhou Zhonghe, an academician of the Chinese Academy of Sciences. Zhou, who was also part of the expedition team and specializes in Mesozoic birds and the Jehol Biota, confirmed Wang’s judgment.

Bird fossils are relatively rare. Zhou Zhonghe explained, “The fossilization process usually requires a water environment, such as oceans or lakes, which increases the likelihood of preservation for aquatic organisms. Since most birds live in terrestrial and forest environments, they need to die near water and be rapidly buried to become fossils.” Such conditions are uncommon for most birds, making their fossil preservation rate relatively low.

Moreover, throughout the course of evolutionary history, early organisms had fewer species and a more limited distribution. Over time, biodiversity and geographic range expanded. As a result, early bird fossils are particularly difficult to find. After the year 2000, Cretaceous bird fossils dating back 120 to 131 million years were discovered in the provinces of Hebei and Liaoning, a period when birds were already widely distributed globally. However, going further back in time, questions remained about the extent of bird distribution during the Jurassic and whether birds existed in Fujian during that era. Zhou admitted, “We didn’t have high expectations – we just wanted to give it a try.”

Xu Xing, director of the Institute of Vertebrate Paleontology and Paleoanthropology and an academician of the Chinese Academy of Sciences, specializes in Mesozoic reptile fossils and stratigraphy. He has been conducting fieldwork since the 1990s. In November of last year, he visited the field site in Zhenghe County. He observed that the surrounding mountains were densely covered with lush green trees and that the quarry was relatively small.

Xu concluded that Fujian’s dense vegetation posed certain challenges for fieldwork. On one hand, fossils are typically preserved within rock formations, and their collection relies on either previous discoveries or the exposure of fossils at the surface, which helps determine the excavation potential of a given area. However, thick vegetation makes it difficult to spot fossil clues. On the other hand, to protect the ecosystem, fossil collection in vegetated areas requires special approval, which increases costs.

Additionally, the overall size of the quarry in Zhenghe County is smaller compared to excavation sites in Liaoning and Hebei. Xu noted, “In Liaoning and Hebei, individual quarries are generally not very large, ranging from 100 to 300 square meters, but there can be hundreds or even thousands of them.” According to Wang Min, the quarry in Daxi Village in Zhenghe County, covers about 300 to 400 square meters and is currently the only one in the area. Xu also pointed out that compared to the rocks in Liaoning, the rocks in Fujian are more prone to fragmentation, making fossil extraction more difficult and reducing the likelihood of preserving good specimens.

Despite these challenging environmental conditions, Wang Min’s team successfully discovered Fujianvenator prodigiosus and the Baminornis zhenghensis in succession.

The specimen of the Baminornis zhenghensis is incomplete, missing its head and preserving only part of its body. However, through laboratory restoration and analysis, researchers gradually gained a clearer understanding of the bird. Its body size was similar to that of a modern cockatoo, weighing approximately 100 grams, and it lived in a humid environment near lakes and swamps.

The most crucial feature of the Baminornis zhenghensis is its short tail, which ends in a pygostyle. A short tail is a key characteristic distinguishing modern birds from reptiles like lizards and crocodiles. Current research suggests that birds evolved from dinosaurs, most of which had long tails. “One of the major questions in the evolution of dinosaurs into birds is when tail shortening occurred,” Wang Min explained. A shorter tail reduces body weight and shifts the center of gravity forward, helping birds maintain stability in flight.

The pygostyle is formed by the fusion of the final few tail vertebrae. Wang further noted, “The appearance of the pygostyle is a landmark event in the structural evolution of modern birds.” The presence of this structure in the Baminornis zhenghensis indicates that the body shape of modern birds had already emerged in the Jurassic period, pushing back the known origin of this feature by 20 million years. Xu Xing added that previously, the earliest known fossils of similar species dated back 130 million years, such as Archaeornithura meemannae from the Cretaceous period found in Hebei, which shares morphological similarities with the Baminornis zhenghensis.

For a long time, most scientists believed that Archaeopteryx was the only bird fossil from the Jurassic period. Previously, Archaeopteryx, which lived about 150 million years ago, was considered the oldest known bird. However, there has been ongoing debate over whether Archaeopteryx should be classified as a bird.

Xu Xing explained, “Archaeopteryx was classified as a bird mainly because of its feathers, as animals with feathers are generally considered birds. However, Archaeopteryx looks like a dinosaur and has a long tail, whereas most birds we are familiar with have short tails.” More importantly, in recent years, scientists in China and other parts of the world have discovered several small dinosaurs resembling Archaeopteryx. These dinosaurs not only had feathers but also shared similar skeletal features, including long tails. Some studies even classify Archaeopteryx as a member of the dromaeosaurid theropods rather than a true bird.

The scientific community has yet to reach a consensus on whether Archaeopteryx should be considered a bird. However, no such debate exists for the Baminornis zhenghensis, as it possesses clear avian characteristics, such as shoulder and pelvic girdles resembling those of some Cretaceous birds. This makes Baminornis zhenghensis the world’s only confirmed Jurassic bird. Xu Xing remarked, “The discovery of Baminornis zhenghensis has opened a window, allowing us to glimpse a Jurassic world that was previously beyond our reach.”

The ancient life forms of Earth remain mysterious, and paleontologists have long sought to answer fundamental questions about the origins, evolution, and extinction of species. Wang Min emphasized, “Understanding how each species originates, goes extinct, and how biodiversity increases provides a crucial perspective for humanity to comprehend the natural world.”

In the study published in Nature, Wang Min’s team also discovered another, less complete bird fossil consisting of a single furcula. This wishbone closely resembles those of ornithuromorphs, a major group of Mesozoic birds that includes modern birds and their closest relatives. Finding this fossil in a 150-million-year-old stratum in Zhenghe suggests that not only did Baminornis zhenghensis inhabit the region, but another bird species, represented by this isolated furcula, also lived there. Wang Min noted, “If this furcula truly belongs to an ornithuromorph, then the emergence of this group can be traced back at least 150 million years. Consequently, more primitive bird species must have appeared even earlier, potentially pushing back the timeline of avian evolution.”

As a branch of evolutionary biology, paleontology explores the origins and evolution of key groups such as birds and mammals, as well as the processes that shaped Earth’s biodiversity. Xu Xing explained that Earth’s early biosphere was vastly different from today’s. The terrestrial ecosystem only took shape as life gradually expanded from oceans to land.

Over time, organisms continuously adapted to new environments. Some terrestrial species eventually took to the skies, necessitating significant morphological, structural, and physiological transformations. Xu Xing emphasized, “This transition – from land to air – is one of the major evolutionary events in Earth’s history. Studying the origin of birds helps us understand how animals adapted to aerial life. The discovery of Baminornis zhenghensis provides new insights into how such creatures came to dominate the planet.”

Exploring ancient biodiversity not only helps reconstruct the origins of life and fill historical gaps but also informs predictions about the future. “Mass extinctions are often linked to geological and environmental changes, which is highly relevant to humanity today,” Wang Min explained. “By analyzing data from Earth’s geological past, we can refine models to predict how climate change might impact biodiversity in the future.”

Questions like “How will a one- or two-degree increase in global temperature affect species diversity?” may find answers in Earth’s geological record. Wang Min believes that this is one of the broader implications of discovering Baminornis zhenghensis – it not only enriches our understanding of the past but also helps humanity anticipate the challenges of the future.

Well, that’s the end of our podcast. Our theme music is by the famous film score composer Roc Chen. We want to thank our writer Hu Yiqin, translator Wang Yuyan, and copy editor Pu Ren. And thank you for listening. We hope you enjoyed it, and if you did, please tell a friend so they, too, can understand The Context.