About 150 million years ago, Europe was tropical and mostly underwater. The entire continent was closer to the equator than it is today, and what is now known as Germany and its neighboring countries was submerged under a shallow inland sea dotted with islands.
‘Strange’ dinosaur prompts rethinking of bird evolution
On one group of islands, there were unusual creatures that did not fit in with the rest of the fauna. These were some of the oldest birds on the planet: roughly the size of crows, with black feathers, and probably inclined to eat insects. These animals were unable to fly, spending most of their time on the ground and occasionally taking to the air, perhaps to escape encroaching predators.1. They also do not resemble modern birds. They had teeth in their jaws and claws at the ends of their wings, features not found in any adult birds today. These animals were German ArcheopteryxThey bore many traces of their dinosaur ancestors.
excavations Archeopteryx They are some of the most famous creatures in history, but this creature is also a mystery. For more than a century, Archeopteryx It was the only bird genus known from the Jurassic Period: the period in which birds first evolved. Many other birds dating back to the age of dinosaurs have been discovered over the past few decades, but they all belong to the later period, the Cretaceous Period: a time when many and diverse species of birds lived around the world. The group’s assets remained lost over time.
Now, researchers have finally identified a second genus of Jurassic birds. Paminurnuwhich was discovered in China and described in February 2025, immediately expanded scientists’ knowledge about the oldest birds. Paminurnu Unlike Archeopteryxreferring to a complex evolutionary story. In parallel, the description is noticeably preserved Archeopteryx The specimen, which had remained hidden for decades, has shed unprecedented light on the first birds. Such discoveries reveal clues about how and why birds evolved, and whether they evolved powered flight only once or several times during the age of dinosaurs.
From ground to air
Today birds are one of the most successful and diverse animal groups, with about 10,000 known species2. They vary from small hummingbirds that can soar in midair to large travelers such as wandering albatrosses, predators such as golden eagles and large flightless creatures such as emus.
Over the past half-century, researchers have demonstrated that birds evolved from dinosaurs: specifically, theropods, the group that includes turkey-sized dinosaurs. Velociraptor And high-rise Allosaurus.
However, reconstructing the evolutionary history of birds has proven extremely difficult. “Birds and bird-like dinosaurs are very rare in the fossil record,” says Jingmai O’Connor, a paleontologist at the Field Museum in Chicago, Illinois.
Blame anatomy for its rarity. “Birds are generally small, with hollow, brittle bones and lightweight skeletons,” says Stephen Brusatte, a paleontologist at the University of Edinburgh in the United Kingdom. This means that their bones are more susceptible to breaking and crushing in harsh environments, such as fast-flowing rivers, where there is a large, skeleton-like skeleton. Tyrannosaurus rexhe might survive.
The discovery of the trifoliate feathers (pictured inset) helps understand how this is done Archeopteryx He flew.Credit: Delaney Drummond/The Field Museum
In view of all this, preservation Archeopteryx Fossils are something of a miracle. The first specimens were discovered in the early 1860s: first a feather, the first fossil feather ever found.3Then a skeleton missing its head. The timing was fortunate: Charles Darwin published it On the origin of species In 1859, he presented his arguments that natural selection led to the formation of new species and, ultimately, radically new types of organisms. the first Archeopteryx The fossil, discovered just a few years later, was a dramatic example of a transitional fossil: an animal with some bird-like features but also some dinosaur-like features.
Arguments have raged for decades around two main questions: Is it possible? Archeopteryx It flies, and is it considered a bird? It had wing feathers that help modern birds fly4. But other aspects of its anatomy were less suitable for sustained flight. “Archeopteryx “It had a long tail, like a raptor,” Brusatte says. “This would have been awkward in flight: modern birds have short, stubby tail bones.”
In the same way, Archeopteryx It does not appear to have had a breastbone to which powerful wing muscles could be attached. “It’s really puzzling,” says Talia Lowe-Merry, an evolutionary biologist at Harvard University in Cambridge, Massachusetts, who has shown that the sternum evolved gradually in later birds.5.
It may be so Archeopteryx He had a breastbone made of cartilage, which was not ossified, but served as a weaker anchor for muscles than bones. “If flight had existed, it would have been less powerful than modern bird flight,” Louis Merry says. As a result, many biologists doubt it Archeopteryx They were poor flyers, like modern chickens.
Missing links
Despite the increasing amount of information about Archeopteryxit can only tell us so much. All the fossils come from Germany, from what were once islands in a shallow sea. Some islands have lagoons filled with calm, often salty, water that you enter Archeopteryx Bodies can fall, slowly bury and petrify. “This is a one-in-a-trillion circumstance,” Brusatte says.
Worse still, it is one point on a very long timeline. Archeopteryx All fossils are about 150 million years old: from the end of the Jurassic Period, which lasted from 201.4 million to 143.1 million years ago. But yet ArcheopteryxThere are no more fossils of birds for millions of years.
A 67-million-year-old fossil turns the bird evolutionary tree upside down
For the later Cretaceous (143.1 million to 66 million years ago), the story is different. In eastern Spain, the Las Hoyas fossil site has produced numerous birds and bird-like dinosaurs since the 1980s. More recently, sites in northeastern China have emerged as a treasure trove of microfossils, including birds, that were part of the Jehol Biota, an ecosystem that existed about 135 million to 120 million years ago.
“There are a lot of Cretaceous birds,” Brusatte says. Many of them are not ancestors of living birds: they belong to groups, such as the enantiornithines, that became extinct at the end of the Cretaceous, in the asteroid-related mass extinction, which also wiped out all non-avian dinosaurs.
Altogether, Cretaceous birds and bird-like dinosaurs are known from East Asia, North and South America, Madagascar, and Antarctica. It is clear that by the Early Cretaceous, birds had diversified and become cosmopolitan.
But the Late Jurassic treasury remained frustratingly empty Archeopteryx – Until discovery Paminurnu.
Jurassic birds II
Since 2022, paleontologist Min Wang, of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, and his colleagues have been exploring a new group of fossils: the Chenghe fauna, in southeastern China’s Fujian province. Within the first year, they found a fossil that they named fujianventure: It was probably a bird-like dinosaur more closely related to birds than to other dinosaurs. fujianventure It had long hind limbs, which suggests it probably spent a lot of time wading in the water. The team dated the Zhenghe fauna to 148 million to 150 million years ago: roughly contemporary with Archeopteryx6.
“This sample gave us a lot of hope,” Wang says. “Maybe we can find some more interesting fossils in that area.” The presence of freshwater animals such as turtles and small fish indicates that the Zhenghe fauna was the preserved remains of a wetland: an ideal place for keeping birds.
The researchers quickly hit the jackpot and described it7 Paminurnu In February 2025. It was a small bird, weighing between 140-300 grams. Even more striking is that the bottom five vertebrae of the tail have fused together to form a short bone called a pygostyle. This is the prevailing norm in modern birds and we also see it in birds of the Cretaceous period, but it is absent in Paminurnufamous contemporary, Archeopteryx.
Wang says this was a surprise. Given how early it is Paminurnu One might have expected to find a transitional phase — “some birds might have a shorter tail but still don’t have a dwarf pattern” — but instead, his team found a Jurassic bird with a fully formed dwarf pattern. He argues that this means that the first birds may have existed previously Archeopteryx and Paminurnu. “This has delayed the emergence of birds much earlier than we thought,” he says. “Is it possible that some middle or early Jurassic birds actually evolved?”
Paleontologist Min Wang points to the fused tail bones, or tibia, of PaminurnuIt is a bird from the Jurassic period that was discovered in China.Credit: Jin Sain/Xinhua/Alamy
“This tells us that birds were already experimenting and developing more complex aerodynamic and flight methods by the end of the Jurassic,” Brusatte says. The truth of that Archeopteryx and Paminurnu They were very different, suggesting that birds were indeed diverse, suggesting an earlier evolutionary history than previously thought.
However, O’Connor cautions against drawing too large conclusions from them PaminurnuBecause early interpretations of new fossils can prove incorrect upon closer examination. “I think we still need to wait to really understand how important these fossils are,” she says.
Anyway, even with paminornis, The Jurassic bird record remains very poor, which means that many questions remain unanswered. “Did birds become cosmopolitan once they arose?” The wonders of Brusate. Pterosaurs and bats, other flying vertebrates, spread quickly, but if Jurassic birds did the same, scientists have yet to find traces.