Frozen in Time: New Fossil Challenges Mammal and Dinosaur Coexistence

By pagewriter

October 5, 2023

The discovery of a 125-million-year-old fossil depicting a mammal biting a dinosaur has shattered the conventional perception of mammals as mere underdogs during the reign of dinosaurs. This remarkable find provides invaluable insights into the complex and diverse ancient ecosystems that existed during the early Cretaceous period.

The fossil in question, unearthed in modern-day northeast China, portrays an intense struggle between two ancient creatures. One of them is the herbivorous dinosaur, Psittacosaurus, known for its parrot-like beak and medium-sized stature. The other is the mammal Repenomamus, a relatively large predator for its time, roughly the size of a badger. Remarkably, Repenomamus is seen gripping Psittacosaurus’ lower jaw with one paw while clutching its hind leg with another, with its teeth deeply embedded in the dinosaur’s ribcage. This interlocked embrace provides a chilling snapshot of a life-or-death battle that transpired millions of years ago.

Traditionally, the prevailing notion was that mammals of this era were passive and subservient to the dominant dinosaurs. However, this fossil challenges that view and suggests a more intricate food web where dinosaurs were not always the hunters, and mammals were not always the prey. The fact that Repenomamus, a mammal only a third the size of Psittacosaurus, was attacking a much larger dinosaur raises intriguing questions about the nature of prehistoric interactions between different species.

What makes this fossil even more extraordinary is the audacity displayed by Repenomamus. The positioning of the bodies and the absence of bite marks on Psittacosaurus’ bones suggest that Repenomamus was not scavenging but actively engaged in an attack. This mammalian predator appears to have possessed exceptional courage and voracity, challenging the conventional image of small, meek mammals hiding in the shadows. Instead, Repenomamus presents us with a glimpse of mammals exhibiting predatory behavior and defying the odds.

Psittacosaurus, the dinosaur caught in Repenomamus’ clutches, was an herbivorous creature with a parrot-like beak designed for consuming plant matter. It belonged to the small to medium-sized category, roughly comparable in size to a small to medium-sized dog. This particular species of dinosaur was prevalent during the early Cretaceous period and played a crucial role in the ancient ecosystem. The interaction between Psittacosaurus and Repenomamus highlights the vulnerability of even fully grown Psittacosaurus individuals to smaller mammalian predators.

mammal v dino.jpegdino v mammal.jpeg

The exceptional preservation of this fossil is attributed to the eruption of an ancient volcano, which resulted in the rapid burial of the battling creatures under layers of ash and mud. The suddenness of the event offers a rare opportunity to study a fossil that captures a dynamic behavior rather than a static anatomy. The fossilized moment frozen in time provides paleontologists with valuable clues about the ancient combat strategies employed by different species.

While the Repenomamus-Psittacosaurus encounter may appear extraordinary, it sheds light on a more elaborate and intricate Cretaceous food web. Paleontologists have traditionally depicted dinosaurs as the dominant predators, but this fossil challenges that notion and reveals a world teeming with diverse interactions. The existence of smaller mammalian predators, similar to Repenomamus, suggests that the Cretaceous ecosystem was more akin to an “ecosystem full of ninjas” than a simple predator-prey dichotomy.

Elsa Panciroli, a paleontologist at the Oxford University Museum of Natural History, remarks on the transformative nature of this discovery. For decades, mammals were portrayed as insignificant creatures, constantly hiding from the menacing dinosaurs. However, recent research, including the findings encapsulated in this fossil, has revolutionized our understanding of mammals during the Cretaceous period. Panciroli emphasizes that the diverse roles and behaviors exhibited by mammals challenge the simplistic narrative of their subordination.

The Repenomamus-Psittacosaurus fossil serves as a poignant reminder of the intricate relationships that existed within ancient food webs. It is essential to recognize that interactions between species during the Cretaceous period were not limited to straightforward predator-prey dynamics. The discovery of Repenomamus actively attacking Psittacosaurus highlights the complexity of these relationships and adds a new layer of understanding to the ecological dynamics of the time.

Studying ancient ecosystems and the interplay between different species offers valuable insights into the evolution of ecological systems over millions of years. The Repenomamus-Psittacosaurus fossil provides a tangible example of the resilience and adaptability of species within changing environments. By examining the past, scientists can gain a deeper understanding of the present and make more informed predictions about the future of our own ecosystems.


It now appears that during the Cretaceous period, some 125 million years ago, a ravenous Repenomamus, an ancient mammal the size of an opossum, pounced on an unsuspecting Psittacosaurus—an herbivorous dinosaur more than three times its size who possessed a beak-like jaws. They were sealed in a near eternal death grip due the the volcanic ash and pumice which covered them from a nearby volcano as they fought.
Oct 14, 2023
Obvious you have never lived on a chicken farm. Woe to any mouse, poisonous snake, cat. Birds are omnivores meaning any insect or other small mammal. The picture depicts basically a rat vs a parrot.
. Maybe visit a chicken farm with free range chickens. many farmers have chickens? It opened my eyes to what savage creatures are egg laying birds. And they eat salads too(green anything & its roots). Modern day, no volcano and basically no bones left.>a source of calcium. They also eat their own eggs if cracked for the calcium and the yolk is gone too.<sheep will ignore dead sheep. Sheep are vegetarians.>
. while I was at my uncles farm I witnessed a mouse, rat, cat and poisonous snake get the losing hand(and eventually disappear completely as everything is eaten). Or Australian chickens R the meanest "mothers" around. The 200 birds kept the yard free of ANY green stuff and would even try to eat Orange tree leaves which is the thickness of a quarter and about the same size. They preferred grass and weeds(and their roots). I never saw a lizard either, as it was not wet enough but no poisonous spiders either. Should a chicken is fair game as they will eat their own.
. Me, basically a city boy learned alot being on a farm for a month. They say the T REX is a lot like a chicken as they BOTH have a "wishbone" which is not in other creatures.
. So, maybe how you view dinosaurs needs a review?
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Artisan -

To your question: I spent a month every summer for years on the farm owned by my old man's cousin. The chickens occupied a key area of the barnyard.

The chicken is one of the most ubiquitous domesticated animals; it is bred for both its egg and meat, and is thought to have originally been domesticated from the red junglefowl (Gallus gallus) native to multiple regions from Southeast Asia to Southwest China. Chicken domestication was previously considered to have occurred in the Indus Valley at around 2000 BC6. However, West and Zhou proposed an earlier origin in Southeast Asia, before the 6000 BC, based on archaeological evidence from China, Southeast Asia, and Europe, and palaeoclimatic evidence in China. Chickens were initially used for rituals, including the use of a crowing **** to proclaim the hour of dawn, and later, various ****-fighting and pet breeds were produced and raised around the globe.

Chickens have played many roles in human societies over thousands of years, most recently as an important model species for scientific discovery, particularly for embryology, virology and immunology. In the last few decades, biomedical models like mice have become the most important model organism for understanding the mechanisms of disease, but for the study of outbred populations, they have many limitations. Research on humans directly addresses many questions about disease, but frank experiments into mechanisms are limited by practicality and ethics. For research into all levels of disease simultaneously, chickens combine many of the advantages of humans and of mice, and could provide an independent, integrated and overarching system to validate and/or challenge the dogmas that have arisen from current biomedical research.

Moreover, some important systems are simpler in chickens than in typical mammals. An example is the major histocompatibility complex (MHC) that encodes the classical MHC molecules, which play crucial roles in the innate and adaptive immune systems. Compared to the large and complex MHCs of typical mammals, the chicken MHC is compact and simple, with single dominantly-expressed MHC molecules that can determine the response to infectious pathogens. As a result, some fundamental principles have been easier to discover in chickens, with the importance of generalist and specialist MHC alleles being the latest example.



Since their domestication, chickens (Gallus gallus domesticus) have been venerated by diverse cultures across the world. Relative to other domestic animals including sheep, cattle and pigs, chickens are currently both the preferred source of animal protein and the most numerous domestic animal.

Domestic chickens were initially derived from the RJF subspecies Gallus gallus spadiceus whose present-day distribution is predominantly in southwestern China, northern Thailand and Myanmar. Following their domestication, chickens were translocated across Southeast and South Asia where they interbred locally with both RJF subspecies and other jungle fowl species.
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