Scientists studying ancient fossil footprints have uncovered important evidence about the evolution of dinosaur locomotion. The research suggests that the ancestors of dinosaurs gradually changed how they walked. Over millions of years, these animals evolved from sprawling reptiles into creatures with a more upright stance. The newly published research studying dinosaur ancestors footprints provides a fresh perspective on the evolution of bipedal dinosaurs.

The international research team, led by Dr Lorenzo Marchetti of the Museum für Naturkunde Berlin, examined fossil tracks from the Italian Dolomites. Their findings have been published in the scientific journal “Palaeontology”.

Ancient Footprints from the Italian Dolomites

The researchers studied fossil footprints discovered in GEOPARC Bletterbach, part of the UNESCO World Heritage Site in the Dolomites. These remarkable tracks date from the Late Permian, before the devastating end-Permian mass extinction approximately 252 million years ago. Fossils of early archosauriform reptiles from this period are extremely rare. Consequently, fossil footprints provide valuable evidence about animals that are poorly represented in the skeletal fossil record.

The researchers reassessed the footprints and established a new trace fossil taxon, Pachychirotherium gardenaensis. This scientific name refers to the robust nature of the tracks and their geographical origins in the Gröden Valley. The footprints represent some of the earliest known evidence of archosauriform locomotion.

A trackway of an early archosauriform. The type material of Pachychirotherium gardenaensis. Scale bar equals 5cm. Picture credit: University La Sapienza of Roma.

Picture credit: University La Sapienza of Roma

From Sprawling Reptiles to Upright Walkers

By comparing Permian and Triassic footprints, the scientists reconstructed important changes in the posture of early archosauriforms. During the Late Permian, these animals generally walked with their limbs positioned outwards from their bodies. This sprawling posture resembles the stance seen in many modern lizards. However, their descendants gradually developed a more upright posture during the Triassic. By the Middle Triassic, this evolutionary transition had become well established.

Other important anatomical changes accompanied this transformation. For example, the middle toes became longer, whilst the forefeet became proportionately smaller. Furthermore, these reptiles increasingly walked on their toes rather than placing the entire foot on the ground. This type of locomotion is known as digitigrady. Birds walk on their toes, whereas humans walk on their toes and heels (plantigrade). Together, these adaptations helped early archosauriforms become more energy efficient and better runners.

A close view of the foot of the flightless bird (Rhea). Note the enlarged middle toe and that this bird walked on its toes. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Important Steps Towards Dinosaur Bipedalism

The study suggests that the evolution of upright posture, digitigrady and adaptations for running occurred gradually. These changes did not happen simultaneously. Instead, they developed over millions of years as archosauriform reptiles diversified during the Permian and Triassic. Such evolutionary innovations helped establish the anatomical foundations for bipedal locomotion in later dinosaurs and their close relatives.

For example, famous theropod dinosaurs such as Tyrannosaurus rex possessed powerful hind limbs and walked on their toes. However, the new research demonstrates that some of the fundamental adaptations associated with dinosaur locomotion originated long before the first true dinosaurs evolved.

The left metatarsal bones of a T. rex (Titus). Theropod dinosaurs walked on their toes. Note the enlarged middle toe. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Fossil Footprints Provide Unique Evolutionary Evidence

Fossilised skeletons help palaeontologists reconstruct the anatomy of extinct animals. In contrast, trace fossils preserve direct evidence of their activities. Footprints can reveal information about posture, walking style and how an animal distributed its weight.

Dr Lorenzo Marchetti emphasised the importance of these discoveries. He explained that fossil footprints preserve remarkable details about archosauriform biology and locomotion. Such evidence is especially valuable when skeletal remains are scarce.

This research highlights the scientific importance of trace fossils. Moreover, it demonstrates how the evolutionary history of dinosaurs can be traced back to their distant Permian relatives.

The Everything Dinosaur team acknowledges the assistance of the Museum für Naturkunde Berlin in the compilation of this article.

The scientific paper: “The new archosauriform track Pachychirotherium and the stepwise acquisition of digitigrady, cursoriality and erect stance in the group between the Permian and Triassic” by Lorenzo Marchetti and Hendrik Klein published in Palaeontology.

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A remarkable new species of feathered dinosaur has been described from north-eastern China. Named Norellraptor barsboldi, this small theropod is helping scientists understand how flight evolved in the Dinosauria. The research suggests that different groups of feathered dinosaurs developed flight-related adaptations independently, rather than following the same evolutionary pathway.

The international research team, which included Italian palaeontologist Andrea Cau, published its findings in the scientific journal “Nature Communications”.

Say Hello to Norellraptor barsboldi

The fossil was discovered in Lower Cretaceous deposits of the Jiufotang Formation in Liaoning Province, China. The Jiufotang Formation is a member of the extensive Jehol Group. It is famous for its exquisite vertebrate fossils, including dinosaurs, pterosaurs and early birds. Palaeontologists have been able to build up a detailed picture of the environment that existed in this part of the world in the Early Cretaceous. Norellraptor barsboldi belonged to the Microraptorinae, a group of small, feathered theropods closely related to birds. These dinosaurs were members of the Dromaeosauridae, a family that also includes Velociraptor and Deinonychus.

To read an article from 2021 about an incredible flying reptile from the Jiufotang Formation: Remarkable Pterosaur Fossil Helps to Define a Genus.

The almost complete fossil skeleton measures approximately fifty-seven centimetres in length. Furthermore, impressions of some of the animal’s feathers have been preserved.

Figure 1 – Fossil specimen of Norellraptor barsboldi (specimen number 130108-MHGU-F4281). Whole specimen (a) with skull in lateral view (b). Close up of the rostrum (c). Close up view of the posterior part of skull (d). Pectoral region (e) and distal end of the tail (f). Scale bar equals 5 cm (a) and 1 cm (b-f). Picture credit: Wang et al. (2026), Nature Communications. Reproduced with the kind permission of Dr Andrea Cau.

Picture credit: Wang et al. (2026), Nature Communications. Reproduced with the kind permission of Dr Andrea Cau

The researchers also examined the microscopic structure of its bones. Their findings indicate that the dinosaur was at least three years old when it died.

Honouring Two Influential Palaeontologists

The scientific name Norellraptor barsboldi honours two distinguished palaeontologists who made major contributions to dinosaur research. The genus name recognises American palaeontologist Mark Norell (1957–2025), renowned for his research into theropod dinosaurs and the evolutionary origins of birds. Meanwhile, the species name honours Mongolian palaeontologist Rinchen Barsbold (1935–2025). His pioneering research transformed our understanding of theropod anatomy and the close evolutionary relationship between dinosaurs and birds.

Both scientists played important roles in advancing research into feathered dinosaurs.

To read more about the contribution to palaeontology made by Mark Norell: Mark Norell and His Dinosaur Discoveries.

Rinchen Barsbold contributing to research into dromaeosaurids: Natovenator – A Semi-aquatic Dromaeosaurid.

Did Dinosaur Flight Evolve More Than Once?

One of the most intriguing questions in vertebrate palaeontology concerns the evolution of flight. Microraptorines possessed several anatomical features associated with aerial locomotion. For example, some members of this group had long feathers on their forelimbs and hindlimbs. These adaptations suggest that certain microraptorines could move through the air, perhaps by gliding or using other forms of aerial locomotion.

However, scientists have debated whether these adaptations were inherited from a common ancestor shared with birds. Alternatively, similar features might have evolved independently in different dinosaur lineages. The discovery of Norellraptor barsboldi provides important new evidence.

Different Evolutionary Pathways to Flight

The researchers compared anatomical features associated with flight in microraptorines and early birds. Their analysis revealed that approximately thirty percent of the evolutionary innovations identified in microraptorines also appeared independently in the bird lineage.

Crucially, these adaptations did not evolve in the same sequence. This suggests that the two groups developed their flight-related anatomy through different evolutionary pathways.

Evolutionary sequences of the derived features shared by Microraptorinae and Avialae mapped onto the Norellraptor barsboldi holotype. Picture credit: Wang et al. (2026), Nature Communications. Scale bar equals 5 cm. Reproduced with the kind permission of Dr Andrea Cau.

Picture credit: Wang et al. (2026), Nature Communications. Reproduced with the kind permission of Dr Andrea Cau

The researchers also investigated bone growth in microraptorines. Their findings suggest that these dinosaurs may have possessed distinctive patterns of limb development. Taken together, the evidence challenges the idea that birds and microraptorines inherited a common flight apparatus or followed an identical developmental programme. Instead, different evolutionary pressures may have shaped the wings and flight-related anatomy of these closely related dinosaurs.

An Important Discovery for Understanding Bird Evolution

The discovery of Norellraptor barsboldi demonstrates the importance of exceptionally preserved fossils in reconstructing evolutionary history. Although birds evolved from theropod dinosaurs, the development of flight was evidently a complex process.

Different dinosaur lineages experimented with anatomical adaptations that helped them exploit aerial environments. However, these adaptations did not necessarily evolve in the same order or serve identical functions. The new research supports the hypothesis that flight-related adaptations evolved independently in different branches of the dinosaur family tree. Further fossil discoveries and detailed investigations into dinosaur bone growth should help palaeontologists test this evolutionary scenario.

Norellraptor barsboldi provides another fascinating piece of evidence in the continuing investigation into the dinosaur origins of birds.

Everything Dinosaur acknowledges the assistance of corresponding author Dr Andrea Cau (OPHIS Museo Paleontologico e Centro Erpetologico, Teramo, Italy) in the compilation of this article.

The scientific paper: Wang, X., Ji, Y., Cau, A. et al. (2026). “Independent assembly of the flight apparatus in a non-avian dinosaur clade” published in Nature Communications, 17, 10074.

https://doi.org/10.1038/s41467-026-77804-6

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