Paleontologists in China have discovered a small Jurassic bird that was likely a land-based predator — like a carnivorous pheasant with killer claws. It had some features of birds and others of dinosaurs, suggesting that the earliest birds had a greater diversity of lifestyles than previously recognized.

Jurassic birds first emerged 150 million to 148 million years ago, and fossils of them are rare, so experts are just starting to understand how early birds diversified and evolved the ability to fly.

The researchers discovered the newly identified Yuezhuornis yangyuanensis in 2024, in the fossil assemblage known as the Upper Jurassic Zhenghe Fauna in southeastern China. It lived 150 million to 148 million years ago, roughly when birds started to appear in the fossil record. The team published their findings Wednesday (Oct. 14) in the journal Nature.

Analysis of the fossilized skeleton revealed the animal was small and weighed about 1.8 pounds (0.8  kilograms). "It was probably as large as a crow," Wang told Live Science via email.

Y. yangyuanensis had a mix of features seen in birds and predatory Deinonychosauria dinosaurs, such as Velociraptor, which are known for their sickle-shaped toe claws. It had deinonychosaur-like hyperextensible toes, with forelimbs that were roughly one-third shorter than its hind limbs. This is odd because modern birds and many other Jurassic paravians — the group that includes bird-like dinosaurs, including the ancestors of birds as well as modern birds themselves — have long forelimbs, linked to giving wings more lift force for taking off.

Y. yangyuanensis also had slender cranial elements and sparsely spaced teeth. These features, alongside the curved claw-like toes that were capable of securing prey, suggest that the animal's diet included meat.

"Its key anatomical features are the combination of dinosaurs' and birds' features: for instance, its teeth, pectoral gird, and especially the hyperextensible, 'sickle-clawed' second pedal digit are similar to that of dinosaurs," Wang said. Meanwhile, he said its slender cranial bones and bird-like pelvis are comparable to early birds.

This combination of features suggests that "the morphological gap between birds and dinosaurs is much smaller than we thought," he added.

Comparisons with 377 living bird species showed that the limb proportions of Y. yangyuanensis were most similar to those of terrestrial birds.

Wang suggested that Y. yangyuanensis was a flightless bird, but not one specialized to live in trees or wade in the swamps in the region. It was a small carnivore, with similar proportions to a pheasant, that was well adapted for running. "I think there are no directly comparable modern birds," he said.

The mosaic of features hints that Y. yangyuanensis may have occupied an ecological niche that was rarely utilized by early birds, and that there wasn't a systematic progression toward flight optimization, Wang said.

Despite being flightless, Wang and his colleagues place Y. yangyuanensis closer in the evolutionary tree to modern birds than to Archaeopteryx, one of the world's first proto birds, which lived about 150 million years ago and is thought to have been able to fly.

This adds to evidence that "the ability to fly arose not once, but several times among disparate groups of carnivorous dinosaurs that are closely related to birds," wrote Fernando Novas, a paleontologist at the Felix de Azara Natural History Foundation in Buenos Aires, Argentina, who wasn’t involved in the study, in an accompanying article in Nature. This includes flight evolving in early birds and in scansoriopterygid dinosaurs, which had membranous folds like the wings of bats, and the four-winged microraptors. Y. yangyuanensis seems to have taken a different road, eschewing the flying ways of its relatives.

"It highlights the extraordinary breadth of ecological and morphological diversification that took place close to the origins of avialans," Wang said.

'> Flightless Jurassic bird was like a carnivorous pheasant with killer claws

The underground impact structure, known as Ames crater, is located in northern Oklahoma and is named after a small town that sits above the submerged crater. At around 10 miles (16 kilometers) wide, it is the fourth-largest impact structure in the U.S.

Ames crater was created when an Eiffel Tower-size space rock slammed into our planet at more than 70,000 mph (110,000 km/h). At the time, the region was covered in a shallow ocean, and the crater was subsequently buried beneath layers of seafloor sediment. Therefore, there are no visible signs of the crater at the surface today. It was only discovered in 1991, when oil prospectors accidentally drilled into it.

Until now, researchers thought Ames crater dated to the Ordovician meteor event around 467 million years ago. During this period, an unusually high number of large space rocks smashed into Earth, likely due to the fragmentation of a single parent body somewhere in space. Scientists found fossils of marine animals in and around the crater that date to around the time of that event.

But in the new study, published July 7 in the journal Meteoritics and Planetary Science, researchers analyzed fracture patterns within tiny rocky fragments known as zircon crystals that were embedded in the underground crater. This revealed that the impact actually occurred 370 million years ago, around 97 million years after the Ordovician meteor event.

"No matter what technique we used, it was coming back to this younger signal," study first author Elizabeth Catlos, a geologist and planetary scientist at the University of Texas at Austin, said in a statement.

Reading crystals

Zircon crystals are tiny pieces of a superdurable mineral known as zirconium silicate. These crystals are scattered throughout most of Earth's rock formations, including most of the oldest known rocks on our planet. The near-industructible crystals are extremely useful to geologists because their internal structure preserves evidence of being exposed to extreme conditions, such as high temperatures and intense pressures.

Analyzing zircon crystals is now one of the primary methods of dating ancient meteor craters, and the technique has led to several other impact dates being revised. For example, in July, researchers in Australia revealed that the North Pole Dome crater was around 500 million years younger than initial studies predicted, and in 2025, experts found that the impact that birthed Scotland's Stac Fada Member structure happened around 200 million years later than earlier research estimated.

The crystals offer insight into what Earth may have looked like shortly after it formed and have recently been used to more accurately date the moon.

"These small crystals allow us to go back in time and learn about the major changes to Earth's ancient landscapes," study co-author Danny Stockli, a geologist and dean of the Jackson School of Geosciences at the University of Texas at Austin, said in the statement. "It would be great to do this for more of the meteor impact sites across the continent so we could get a more accurate timeline for these major events."

"This is where the impact belongs"

The crater's new age takes it firmly out of the Ordovician meteor event and places it into the Frasnian-Famennian mass extinction event, also known as the Kellwasser event or the Late Devonian mass extinction.

During the Frasnian-Famennian event, which began around 372 million years ago and lasted for several million years, as much as half of all marine life went extinct as Earth's oceans were depleted of oxygen. The die-off, which was most likely triggered by global cooling due to increased levels of volcanic activity, is often cited as one of the five major extinction events in Earth's history.

The researchers emphasized that the Ames impact was not the cause of the Frasnian-Famennian event. However, they noted that the fallout from the impact, which would have injected huge clouds of dust into the air, may have contributed to the atmospheric cooling effect in the region.

It is an important reminder that the ability to accurately date specific events like this can inform our understanding of wider global patterns and trends, the researchers wrote.

"With this research, we're basically taking a major pawn out of the Ordovician Meteor Event and dumping it into the Frasnian-Famennian event, and saying, 'This is where this impact belongs,'" Catlos said.

The new study was dedicated to co-authors Andrew Parisi and Michael Brookfield, who sadly died before it was published.

'> One of America's biggest meteor craters is 100 million years younger than we thought — and coincided with a global extinction event case report. However, a CT scan showed no signs of swelling or hemorrhage in her head. The doctors attempted a lumbar puncture (also called a spinal tap) but failed to collect any cerebrospinal fluid that they could test for irregularities.

The doctors judged the girl to be too medically unstable to be referred to the hospital's psychiatric ward, so she was admitted to the general pediatric department. Pediatric neurologists suggested an electroencephalogram (EEG), a test that measures electric signaling in the brain, but this revealed no further clues.

On her second day in the hospital, the girl entered a complete catatonic state. Her specific symptoms were not described in the report, but in general, catatonia disrupts how a person processes and reacts to the world around them. Catatonic patients often stop moving and speaking. Doctors treated the patient with lorazepam, which slows down nervous-system signaling, and her catatonia subsided in days.

Meanwhile, interventional radiologists performed a successful second lumbar puncture, but the girl's cerebrospinal fluid appeared normal in the initial panels they ran.

After the patient had spent eight days in the hospital, psychiatrists recommended that the girl be transferred to their ward. However, this was not possible because she developed problems with feeding herself. Her continued psychotic symptoms were treated with the antipsychotic drug olanzapine.

The diagnosis: While initial tests of the girl's cerebrospinal fluid did not show signs of meningitis or other abnormalities, a later test came back positive for autoantibodies — immune proteins that target healthy tissues instead of foreign invaders. These antibodies targeted neuronal intermediate filament (NIF), a protein that helps give nerve cells structural support.

Based on this finding, the patient was diagnosed with autoimmune encephalitis, a condition in which the body produces antibodies that attack nervous tissue, leading to harmful inflammation that can cause psychiatric symptoms.

Autoimmune encephalitis is often triggered by a tumor; proteins produced by the growth can resemble proteins within nervous tissue, and the immune system develops a harmful response against the latter while attempting to fight the tumor. The doctors performed MRIs and a PET scan to look for tumors, but they did not find any.

The treatment: The girl received intravenous infusions of a steroid to reduce inflammation, as well as immunoglobulin — antibodies from healthy donors that are often used to calm autoimmune reactions. She also got an infusion of rituximab, a drug that kills B lymphocytes, a type of white blood cell that makes antibodies like the ones attacking the girl's neurons.

In addition to these infusions, the girl underwent five sessions of plasmapheresis over the next month. In that procedure, blood is drawn from the body, a machine separates plasma (the liquid portion of blood) from blood cells, and the extracted plasma is substituted with a replacement fluid before that blood is returned to the patient. This treatment can help rid the body of autoantibodies.

The girl was discharged after having spent almost two months in the hospital. She was treated with ongoing prescriptions of olanzapine and lorazepam, as well as prednisone and monthly immunoglobulin treatments. As her symptoms improved over the following year, she stopped taking the psychiatric drugs but continued her immunotherapy.

What makes the case unique: Autoimmune encephalitis is rare. One study conducted in the U.K. suggests it affects only 5 to 8 out of every 100,000 people. Additionally, most data about the condition in pediatric patients comes from cases caused by autoantibodies that target NMDA receptors, which detect a key chemical messenger in the brain, rather than NIF.

The case report did not name a specific trigger for the girl's condition, but the authors noted that anti-NIF autoimmune encephalitis has been documented in adults following infections, including certain tick-borne bacterial infections, HIV and COVID-19. Cases associated with these infections are rarer than those linked to tumors.

The doctors did not attribute the teen's case to a specific infection, but her family did report that she'd had a cough three weeks before going to the emergency room. The family had visited the Philippines, and the girl and multiple relatives came down with the same illness.

For more intriguing medical cases, check out our Diagnostic Dilemma archives.

This article is for informational purposes only and is not meant to offer medical advice.

Can you guess the diagnosis in these strange medical cases? Find out with our diagnostic dilemma quiz!

'> Teenager's rare autoimmune disorder caused her to hallucinate a flying green dinosaur

Laboratory analyses of specimens that died this year tested positive for the pathogenic bacterium Erysipelothrix rhusiopathiae, environmental authorities in Chubut province told Live Science. E. rhusiopathiae was first identified in southern right whale calves in 2013, but scientists don't know what might have changed this year to cause an infection-driven die-off of this magnitude.

Researchers say they need to quickly find the answer to better understand the changing threat this species faces, the risk to the wider ecosystem and humans, and what can be done to manage it.

"The battle between living organisms and pathogens is constant," said Carla Fiorito, a researcher at the Center for the Study of Marine Systems (CESIMAR) who previously identified the bacterium in right whales. "But for this to happen now, there must have been a shift in the balance between the agent, the host, and the environment," she told Live Science.

Record-breaking number

The first dead calves appeared on the beaches of Península Valdés in June, at the start of the breeding season, which runs through to December. Península Valdés is located in Chubut province, on the coast of northern Patagonia.

In a typical year, calf mortality reaches 20% to 30% of a cohort from various causes, including infections. But this year's losses have already far surpassed that.

In September, 409 calves were counted among a total of 1,375 southern right whales during a survey conducted by CESIMAR's Marine Mammal Laboratory. With more than 300 deaths already recorded, the die-off represents an exceptional proportion of these calves. The final figure will be released by the Southern Right Whale Health Monitoring Program in December.

Scientists have responded by expediting routine research to determine what's different this year to previous years.

"Samples were sent for analysis earlier than usual — typically, they are analyzed at the end of the year — because the higher-than-usual mortality is a cause for concern," said Víctor Fratto, the director of the Native Wildlife Rescue Program and a contributor with the whale monitoring program. "What those samples are showing is that the calves died from erysipelas," he told Live Science.

A known bacterium full of unknowns

Erysipelas is a bacterial infection that affects the skin. In its most severe form, it can spread through the bloodstream and cause a systemic infection, damaging vital organs and sometimes leading to death. Animals that catch the disease, for example through a wound, may develop characteristic skin lesions, which are rhomboid or rectangular in shape, caused by alterations in the blood vessels.

The bacterium that causes erysipelas, E. rhusiopathiae, is not exclusive to whales. It can be found in marine environments and in a wide variety of animals, including fish, crustaceans and birds. Pigs are one of its natural reservoirs.

"It is a ubiquitous and opportunistic bacterium," Fiorito said. (The human illness of the same name is different and caused by Group A streptococcal bacteria, although humans can also catch the E. rhusiopathiae form of the illness.)

The presence of E. rhusiopathiae does not necessarily mean an animal is diseased. Yet many questions remain about E. rhusiopathiae in whales.

"We don't know much about the bacterium itself; we don't know which serotypes are present in the whales, or how common it is in healthy animals or other species," Fiorito said. "There is also no data on the environment."

Calves are especially vulnerable because their immune systems are still developing and they spend more time at the surface than adults do, exposing them to more attacks by gulls, which can transfer the disease.

"The working hypothesis is that the gull is the vector: Pecking causes wounds on the back, allowing the bacteria to enter," Fratto said. "The bacteria might already be present on the skin, or they could be carried on the beak of a gull that had previously pecked another whale suffering from erysipelas."

The potential role of gulls

Attacks by kelp gulls (Larus dominicanus) on southern right whales were first recorded at Península Valdés in the 1970s. The behavior began with just a few individuals in Patagonia's San José Gulf and became increasingly frequent over time, Ricardo Bastida, a marine biologist and professor emeritus at the National University of Mar del Plata who has studied these cetaceans for more than four decades, told Live Science. The birds also began scavenging the carcasses of stranded whales, Bastida said

Gull populations have grown and new breeding colonies have emerged in the region thanks to increased food availability linked to fishing activities and discarded catch, he noted. However, the attacks alone do not explain the 2026 mortality event: They have been occurring for decades, and gulls are a regular part of the ecosystem.

Fratto said that swabs will be taken from gulls to check for the presence of E. rhusiopathiae and assess whether the results could help develop a management strategy for the species.

Diego Rodríguez, a marine biologist at the National University of Mar del Plata, said that research must go beyond the dead calves and examine the ecosystem's fauna to determine where the bacterium is present and how it might be circulating. "It is far more likely that [the die-off event] is linked to cross-infection," Rodríguez told Live Science.

What changed this year?

The major question for scientists is what might have changed this year to cause a bacterium already present in the ecosystem to trigger a die-off of this magnitude. Experts told Live Science they believe the phenomenon could be the result of several factors acting simultaneously.

"The bacterium was present, but this year it resulted in a widespread infection, making this event unusual," Mariano Coscarella, a researcher at the Marine Mammal Laboratory at CESIMAR, told Live Science. "It is a major step forward to have a fairly clear idea of what caused the disease, but we do not know what changed."

One factor could be the environment. Changes in water temperature, salinity, pH or rainfall could alter the conditions under which infection occurs. There could also be changes in food availability, affecting the mothers' body condition and the vulnerability of their calves. Another possibility is that the pathogen itself has changed — for instance, through the emergence or increased circulation of a more virulent strain or a different serotype, Fiorito said.

The El Niño phenomenon could also play a role by altering oceanographic conditions and food availability, although the researchers said there's insufficient evidence to link it to the die-off.

It is too early to determine what impact this die-off will have on the southern right whale population. Rodríguez suggested that losing such a large proportion of a season's calves could have demographic consequences. "It is very risky to predict what will happen in the future at this stage, but clearly, this year's cohort of live-born calves will essentially be absent from the adult records of future populations," he said.

Coscarella is more cautious. Southern right whales are extremely long-lived, and calves represent only a fraction of the population. Therefore, a single season of exceptionally high mortality does not necessarily mean the population will go into decline, he argued. "What would be concerning is if there were two, three or four episodes like this," he noted.

The event also has public health implications. Fiorito pointed out that erysipelas can infect humans, usually through skin wounds. The whales' carcasses could also pose a risk of exposure to anyone coming into contact with them, as could seawater for people swimming in the area.

Help us improve Live Science Pro: We're always trying to make our content better. Leave us feedback about Pro here.

'> Hundreds of whale calves have mysteriously died in Patagonia — and scientists are racing to find out why