Not all early birds evolved toward better flight, Jurassic fossil suggests

Chinese Academy of Sciences Headquarters

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Photograph of the fossil skeleton of the new Jurassic bird, Yuezhuornis yangyuanensis, from China.

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Credit: Image by Min Wang.

For early birds, evolution wasn’t always about becoming better flyers. This conclusion is supported by the recent discovery of a remarkably well-preserved, 150-million-year-old bird fossil from Fujian Province, China, which is challenging long-held assumptions about early bird evolution.

A study published in Nature discusses the newly discovered species, Yuezhuornis yangyuanensis, which lived during the Late Jurassic period (150–148 million years ago). The research suggests that the evolution of the avian body plan was not a straightforward progression toward improved flight capabilities, but a complex process involving the exploration of different ecological niches, including some that did not require flight.

Discovered in the recently recognized Zhenghe Fauna of southeastern China by researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences (CAS) and the Fujian Institute of Geological Sciences, the crow-sized fossil represents the earliest known example of flight loss in the evolutionary history of birds.

Yuezhuornis challenges the traditional view that the avian body plan evolved almost exclusively under selective pressures associated with flight. Instead, it exhibits a striking mosaic of primitive and derived features, combining characteristic avian traits with features inherited from earlier dinosaur ancestors.

The fossil preserves closely packed, serrated teeth, which are typically found in deinonychosaurs but not birds. Most notably, Yuezhuornis possessed a hyperextensible second toe with a sickle-shaped claw, a characteristic feature of deinonychosaurs, including dromaeosaurids and troodontids.

“When we examined Yuezhuornis, we were struck by its extraordinary mix of features,” said Dr. WANG Min, corresponding author of the study. “It possesses bird-like pelvic and hindlimb structures yet retains the specialized predatory foot and teeth of a small meat-eating dinosaur. It shows us that early bird evolution was far more complicated than we previously realized.”

To determine where this enigmatic species fits on the evolutionary tree, the research team conducted comprehensive phylogenetic analyses using both maximum parsimony and Bayesian tip-dating methods.

“The results consistently placed Yuezhuornis firmly within Avialae (the group containing modern birds and their closest extinct relatives), just crownward of Archaeopteryx and as a sister taxon to Zhengheornis,” said Dr. ZHOU Zhonghe, a co-author of the study.

Given its unique anatomy, the team investigated the ecological niche of Yuezhuornis using ecomorphometric and multivariate statistical analyses. The analyses revealed that the limb proportions of Yuezhuornis were similar to those of living terrestrial birds and some non-avialan paravians, suggesting a terrestrial, flightless lifestyle and shedding new light on the ecological diversification of early-diverging avialans.

The discovery of a flightless, ground-dwelling bird from the Late Jurassic challenges the notion that aerodynamic selection was the dominant force shaping early avialan evolution. Instead, it suggests that some early birds followed evolutionary paths that did not favor flight, highlighting the remarkable ecological and morphological diversity that emerged during the early evolution of birds.

The ongoing discovery of early avialans also highlights the potential of the Zhenghe Fauna to shed light on a poorly documented stage of Jurassic bird evolution.

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Journal

Nature

DOI

10.1038/s41586-026-10972-z 

Life reconstruction of the Late Jurassic bird Yuezhuornis yangyuanensis.

Eco-morphometric disparity of Yuezhuornis and other Jurassic paravians. 

Evolutionary tree showing the position of Yuezhuornis as one of the earliest branching of birds. The right panes show the fore limb evolution across dinosaur-bird transition.

Credit

Image by Min Wang.

 

Insect declines threaten wildlife far beyond insect world

Major global analysis shows insects provide diverse benefits for other animals – from food and shelter, to protection and even medicines.

UK Centre for Ecology & Hydrology

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From grizzly bears and chimpanzees to geckos and poison dart frogs, the lives of tens of thousands of animal species depend on insects and other invertebrates not just for food. They provide, homes, medicines, sanitation and chemical self-defence, often living alongside each other in mutually beneficial relationships.  

Scientists are now warning that widespread insect declines will therefore have far-reaching impacts on other species. An international research team carried out the most comprehensive global scientific analysis to date of the impacts of insects on wildlife, led by the UK Centre for Ecology & Hydrology (UKCEH) and Binghamton University, USA. 

The scientists reviewed evidence from almost 300 studies published over the past 75 years relating to land and freshwater wildlife, including mammals, birds, amphibians, reptiles and fish. It found nearly three-quarters of studied wildlife species eat invertebrates – mainly insects – and over two-fifths exclusively so.

Many animals also rely on foods that exist only because insects pollinate plants or disperse seeds.  Some species have developed remarkable adaptations for capturing them, from the projectile tongues of amphibians and chameleons to birds that have learnt to remove bee stings before eating them. 

But the study, published in Nature Reviews Biodiversity, also identifies many ways that insects support wildlife beyond simply providing food. 

• Providing homes: Wildlife use insect-built structures, particularly termite mounds and ant nests, for shelter, protection from predators, breeding grounds or laying eggs.   
• Chemical defence: Some animals, such as poison dart frogs, accumulate toxins from the ants and beetles they eat and secrete them, making themselves less appealing to predators.
• Health and sanitation: Insects can reduce disease risk through the removal or drying of dung, which also kills parasites. Beetles prey on the larvae of blowfly and other pests, protecting birds and mammals from biting insects and disease. Chimpanzees apply insects to open wounds and some birds, reptiles, amphibians, rodents and primates use ants for grooming. 

The paper’s co-lead author Dr Rob Cooke, a senior ecologist at UKCEH, said: “Our study presents the most holistic picture of interactions between insects and wildlife to date. It highlights the remarkable and often overlooked ways that insects support other animals, and the extraordinary relationships between them.  

“Widespread insect declines globally are likely to have far-reaching effects on wildlife. Beyond reducing an essential food source, losses of insects risk changing ecosystems, disrupting pollination and seed dispersal, weakening sanitation, and altering the many interactions that help ecosystems function.  

“We therefore hope our research strengthens the message that protecting insect populations is essential for protecting wider biodiversity.”

Helpful housemates 

Some species of wildlife live alongside insects in mutually beneficial relationships. Moths have been found in owl and kingfisher nests, where they decompose fur, crushed feathers, pellets and faeces. They also live on the backs of brown-throated sloths where they deposit nitrogen in their fur and spur algal growth, a key food source for their hosts. 

The study does, though, also point out the negative impacts. Although insects generally do not eat other animals, it does occur, such as dragonfly nymphs eating tadpoles and small fish and mantids sometimes capturing hummingbirds and other small birds. Ants and wasps have been reported to attack lizards, birds and mammals. 

Meanwhile, different species of mosquitoes transmit avian malaria and West Nile virus to birds, or fungus to frogs, and fleas pass on pathogens to mammals. 

Dr Eliza Grames of Binghamton University, co-lead author of the paper, concluded: "Changes in insects can have massive consequences for food webs and ecosystems. Declines in insect populations could risk destabilizing some of the most fundamental processes that the natural world depends on." 

ENDS

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Journal

Nature Reviews Biodiversity

DOI

10.1038/s44358-026-00201-w

Method of Research

Systematic review

Subject of Research

Animals

Article Title

The importance of insect biodiversity for vertebrates

 

Insects are essential to vertebrate life — as food, shelter and medicine

Binghamton University, State University of New York biologists co-author a review paper on the importance of insect diversity in a time of decline

Binghamton University

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A new paper featuring faculty at Binghamton University, State University of New York, reveals that vertebrates like sloths rely on insects for a variety of purposes.

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Credit: “Hoffmann's Two-toed Sloth (Choloepus hoffmanni) 霍夫曼兩趾樹懶 & Sloth Moths (Cryptoses choloepi) 樹懶蛾” by Dash Huang, CC BY-NC-SA 2.0

While insects provide an essential food source for many vertebrate species, they’re more than just a protein-laden snack.

Chimpanzees use them to sterilize wounds, and herons as fishing bait. Sloths rely on moths to maintain the algae in their fur, which they then eat. Birds and reptiles lay their eggs inside the temperature-controlled sanctuary of termite mounds, while some desert frogs reside in ant nests because of the humidity.

“Insects are sometimes called the ‘little things that run the world’ because they are so important to life on Earth,” said Binghamton University, State University of New York Assistant Professor of Biological Sciences Eliza Grames, the co-lead author of “The importance of insect biodiversity for vertebrates,” published Sept. 30 in Nature Reviews Biodiversity. “We often hear about their importance as pollinators, or decomposers, or food for insectivores like birds and bats, but we forget about all the other things they do for us and for other species.” 

A collaborative effort with authors from eight countries, the review paper was led by Grames along with Rob Cooke, an ecological modeler at the UK Center for Ecology and Hydrology, and UConn Professor of Ecology and Evolutionary Biology Chris Elphick. 

Additional Binghamton authors include Assistant Professor of Biological Sciences Lindsey Swierk and biological sciences alumni Julianna Yager, MS ’25, and Suyeon Jang, ’25. Jang, an undergraduate with a painting minor, also created the paper’s main illustration as an independent study project. 

The review article consolidates hundreds of disparate studies conducted across decades, highlighting the importance of insect biodiversity in supporting vertebrate life. The project began in 2022 with the creation of the National Science Foundation-funded Status of Insects: An International Research Coordination Network, a direct result of Grames’ work as a doctoral student in Elphick’s lab. 

A better understanding of the diverse roles that insects play in the lives of vertebrates is essential for designing effective conservation strategies. Elphick, an ornithologist, said that he hopes the review will foster increased collaboration between scientists who study vertebrates and those who study insects.

“If you want to have vertebrates, then you’ve got to be thinking about insect conservation, and we don’t do that nearly enough,” he said.

There are an estimated 14 to 30 million species of insects in the world, and they play a major role in the health and function of ecosystems. They provide food to species ranging from hummingbirds to grizzly bears, enable the existence of other food sources through pollination, and produce substances such as honeydew, honey, and wax that are also consumed by other species.

Birds use spider and insect silk in their nests, which they sometimes situate near stinging insects such as wasps for extra protection. More than 200 bird species use crushed ants for grooming, and a variety of vertebrate species time their breeding season to coincide with seasonal insect abundance. Go back far enough, and insects once lived inside dinosaur nests, cleaning them out; it’s a service they still perform in some owl and kingfisher nests, according to Grames. 

But few scientific studies consider the decline of insect populations on vertebrate species, other than as a reduction in a species’ food supply, according to the paper. Some insect populations have experienced alarming declines in recent decades, which will ultimately affect the vertebrate species that rely on them. 

“We’re losing insects at a rate of about 1-2% per year,” said Grames. “When you scale that up across a few decades, we’re talking about a major change to ecosystems. Insect conservation should be a top priority for anyone worried about the future of biodiversity.”

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Journal

Nature Reviews Biodiversity

Method of Research

Literature review

Subject of Research

Animals

Article Publication Date

30-Sep-2026

 

Fossils from embryo to adult suggest how enigmatic, bird-like troodontid dinosaur grew

Study of Montana hip and leg bone fossils might support designation as primary example of Troodon formosus

PLOS

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Geologic context and preserved material for Troodon described here. Chronologic placement of Two Medicine Troodon specimens after Rogers et al. (A). Graphical representation of preserved pelvic and hindlimb material, with silhouettes reflecting relative size of the individuals preserved (B). Abbreviation: Ma, millions of years ago. Troodon silhouettes made with reference to work by Scott Hartman (https://creativecommons.org/licenses/by-nc-sa/3.0/). 

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Credit: Varricchio, Caldwell et al., 2026, PLOS One, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

Analysis of fossilized remains from dinosaurs known as troodontids reveals how one species’ hip and leg bones may have developed over its lifespan, from embryo to adult—with potential implications for resolving longstanding taxonomic challenges. David Varricchio of Montana State University, US, and Heath Caldwell of North Carolina State University, US, present their findings in the open access journal PLOS One on September 9, 2026.

Troodontids were a family of bird-like dinosaurs with long legs, large brains and eyes, and feathers. Fossils indicate they lived in North America in the late Cretaceous period. For decades, a limited amount of fossilized remains hampered understanding of troodontids, but recent new fossil discoveries are advancing the field.

To help fill in the blanks, Varricchio and Caldwell analyzed pelvic and hindlimb fossils collected in western Montana, US, in an area thought to have been a coastal plain when the dinosaurs lived there between about 75 to 78 million years ago. The fossils are thought to represent individuals of the species Troodon formosus at various stages of its lifespan, from embryo to adult, enabling the researchers to reconstruct how a typical individual’s hip and leg bones may have developed over time.

The analysis suggests that, during its lifetime, T. formosus underwent specific changes in the texture, shape, and relative proportions of different parts of these bones. For instance, the ratio of femur to tibia length was higher in adult fossils than in juveniles. These changes appear to have occurred at consistent growth stages, suggesting a limited influence of environmental factors. The analysis also suggests that adults varied distinctly in size and, in line with prior research, suggests foot problems may have been common in the species.

The researchers say these findings support designation of a specific subset of the remains—a collection of pelvic and hindlimb fossils from juveniles and adults—as the primary representative, or “type specimen,” of T. formosus. This would replace a single tooth that has been the type specimen for decades and could help resolve longstanding concerns about the validity of the Troodon genus. The authors note that this assignment would depend on a decision that is currently pending from the International Commission of Zoological Nomenclature.

Further research could help deepen understanding of the lifestyle of Troodons, such as how they walked or ran.

The authors add: “In this study, we investigated the morphology of the hindlimb and pelvic skeleton for the bird-like dinosaur Troodon formosus from a relatively large sample of embryonic to skeletally mature individuals. Analysis of these bones provided an unprecedented opportunity for understanding the biology of a historically enigmatic group of animals and will serve as a valuable resource for paleontologists for years to come.”

 

 

The "killing claw" (pedal ungual II) from Troodon from a juvenile (top) and adult (bottom).

 

Embryonic pelvis and femur of Troodon formosus. Embryonic pelvic elements for Troodon (MOR 246−11) in lateral view. Abbreviations: fe, femur; il, ilium; isp, ischiadic peduncle; pp, pubic peduncle; ps, pubis.

Credit

Varricchio, Caldwell, 2026, PLOS One, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

  

Reconstruction of Troodon formosus by Clarissa Koos (hi-resolution image available upon request from article authors).

Credit

Clarissa Koos, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

Author interview: https://plos.io/4yCXHXB

In your coverage, please use this URL to provide access to the freely available article in PLOS One: https://plos.io/4wRUe65

Citation: Varricchio DJ, Caldwell HR (2026) Pelvic and hindlimb osteology and ontogeny of a troodontid from the upper member of the Two Medicine Formation (Cretaceous) of Montana. PLoS One 21(9): e0356249. https://doi.org/10.1371/journal.pone.0356249

Author countries: USA.

Funding: The author(s) received no specific funding for this work.

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Journal

PLOS One

DOI

10.1371/journal.pone.0356249 

Method of Research

Observational study

Subject of Research

Animals

Article Title

Pelvic and hindlimb osteology and ontogeny of a troodontid from the upper member of the Two Medicine Formation (Cretaceous) of Montana

Article Publication Date

9-Sep-2026

 

New evidence to help solve how earliest birds took flight

University of Southampton

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An illustration of Archaeopteryx.

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Credit: Mark Witton

The first ever bird to inhabit the Earth used its robust hind legs to make two or three powerful leaps while flapping its way to flight, according to a study by the University of Southampton.

Scientists have debated for over a century how Archaeopteryx – a 150 million year old reptile-like bird – was able to take-off into the air.

The creature, which represents an important evolutionary step between non-avian dinosaurs and birds, was incapable of achieving flight with just a single jump as modern birds do.

Archaeopteryx had limited shoulder mobility and no breastbone, which hampered its ability to quickly reach flight speed. Exactly how it left the ground has, until now, remained a puzzle.

“Archaeopteryx is the first real bird,” explains palaeobiologist at the University of Southampton, Dr Neil Gostling. “It was covered in feathers and possessed wings, but also retained a number of distinctly dinosaur features, such as a long bony tail, claws on separate fingers, and teeth in a beakless jaw. It wasn’t a particularly well developed ‘bird’ compared to those we know today.”

Professor of Biomechanics at Southampton, Markus Heller, adds: “We know Archaeopteryx couldn't rely on its wings to take off – with no keeled sternum, and a shoulder that couldn't lift the wing above the back – so we asked what its legs could contribute. It turns out that is where take-off is won: the legs generate the force, and the wings take over afterwards.”

Several mechanisms for how early birds first left the ground have been suggested over the years, including flapping while running up an incline, and gliding from a height – for example from a tree, or a cliff.

These methods are difficult to test experimentally, but following observations made by the late Dr Colin Palmer, the team combined sophisticated computer modelling with these observations from living birds, such as gulls, magpies, crows and finches, and fitted this to Archaeopteryx’s anatomy. By analysing joint moments at the hip, knee, and ankle, alongside muscle capacity, they estimated the ancient bird’s take-off velocity.

The scientists, including Dr Pauline Provini from the Muséum National d’Histoire Naturelle in Paris, concluded that Archaeopteryx could have achieved its minimum sustainable flight speed in as few as two or three leaps, without requiring the energetically demanding single leap used by modern birds.

“Our findings show that a mid-sized, 400g Archaeopteryx could have achieved a sustainable flight speed of seven metres per second with three bipedal leaps, or with two bipedal leaps with a downward flap between jumps.” said Dr Erik Meilak, a former PhD researcher at the University of Southampton who carried out the study.

“All birds push with their legs when they take-off,” explains Dr Gostling. “In fact up to 90 percent of the force required to get off the ground comes from the legs and then the wings take over.

“Archaeopteryx would have either taken off with a leap, leap, leap and then lots of flapping, or a leap, a flap, another leap and more flapping.

“Although today’s birds can take-off with just one leap, we still see many, such as crows, magpies and seagulls, also using the multiple hop technique. They use one leap if startled, stressed or threatened, or – like their ancestors – two or three or more if they are saving energy.”

The researchers findings are published in the journal Developmental Biology.

Ends
 

Notes to editors
 

1. The paper ‘Hop, hop and away: On the take-off of Archaeopteryx using a multiple leaping mechanism’ is published in the journal Developmental Biology, DOI 10.1016/j.ydbio.2026.07.018 and can be read here: https://doi.org/10.1016/j.ydbio.2026.07.018
    
2. For interviews or more information contact Peter Franklin, Media Manager, University of Southampton. press@soton.ac.uk +44 23 8059 3212 or Dr Neil Gostling, n.j.gostling@soton.ac.uk 07528 498792.
    
3. Images can be downloaded here: https://safesend.soton.ac.uk/pickup?claimID=KtrxWv8XRahx9FpN&claimPasscode=Khyf3nAJddcwMn3a&emailAddr=286425
    
4. Authors on the paper are: Dr Erik Meilak, Dr Neil Gostling, Dr Colin Palmer and Professor Markus Heller, all of the University of Southampton, UK, and Dr Pauline Provini of the Muséum National d’Histoire Naturelle in Paris, France.
    
5. This Manuscript is of even more importance to the authors because Dr Colin Palmer passed away at the end of last year, and this project came about with him at the centre. A photo of Colin is available.
    
6. For more about Biological Sciences at the University of Southampton visit: https://www.southampton.ac.uk/about/faculties-schools-departments/school-of-biological-sciences
    
7. The University of Southampton drives original thinking, turns knowledge into action and impact, and creates solutions to the world’s challenges. Our academics are leaders in their fields, forging links with high-profile international businesses and organisations, and inspiring a 25,000-strong community of exceptional students, from over 135 countries worldwide. Through our high-quality education, the University helps students on a journey of discovery to realise their potential and join our global network of over 300,000 alumni. www.southampton.ac.uk

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Journal

Developmental Biology

DOI

10.1016/j.ydbio.2026.07.018 

Method of Research

Observational study

Subject of Research

Animals

Article Title

Hop, hop and away: On the take-off of Archaeopteryx using a multiple leaping mechanism

Article Publication Date

15-Aug-2026

 

An illustration of how Archaeopteryx could have taken off.

Credit

Science Graphic Design

 

A model of Archaeopteryx.

Credit

Karen Fawcett