Some mammals attacked dinosaurs, and they often won the battle •
Mammals attacked dinosaurs! Repenomamus (mammal) biting the ribs of Psittacosaurus (dinosaur). Credit: Michael Skrepnick

Some mammals attacked dinosaurs, and they often won the battle

A very intriguing fossil find is shaking up the scientific world, unearthing fresh evidence about predator-prey relationships from a time when dinosaurs reigned supreme. An extraordinary fossil from approximately 125 million years ago depicts a mammal attacking a dinosaur in a fierce confrontation.

The fossil tells the story of a fight for survival between a carnivorous mammal and a larger dinosaur that subsisted on plants. The fossil originates from the Cretaceous era. It is nothing short of a time capsule that throws light on the predator-prey dynamics of that period.

Dr. Jordan Mallon is a palaeobiologist with the Canadian Museum of Nature. As one of the researchers involved in the study, he reveals, “The two animals are locked in mortal combat, intimately intertwined, and it’s among the first evidence to show actual predatory behaviour by a mammal on a dinosaur.”

This research was recently published in the journal Scientific Reports. He has incited intense debate and altered perceptions about the assumed dominance of dinosaurs in the Cretaceous.

Team is amazed that mammals attacked dinosaurs

Previously, most people widely believed that mammals posed little threat to dinosaurs in the Cretaceous. This period of history was marked by dinosaur dominance. This newly discovered fossil refutes that notion. It now proudly holds a place in the collection of the Weihai Ziguang Shi Yan School Museum in China’s Shandong Province.

The well-preserved fossil reveals the smaller predator as a badger-like creature named Repenomamus robustus. This mammal would attack dinosaurs, and held its own in the animal kingdom of the time.

This despite being considerably smaller than a dinosaur. By Cretaceous standards, Repenomamus was one of the largest mammals, living during a period when mammals were yet to rule the Earth.

Researchers identified the prey as a species of Psittacosaurus, a plant-eating dinosaur about the size of a large dog. Psittacosaurs ranked among the earliest known horned dinosaurs. They roamed Asia from around 125 to 105 million years ago during the Early Cretaceous.

Dr. Mallon adds, “The co-existence of these two animals is not new, but what’s new to science through this amazing fossil is the predatory behavior it shows.”

Fossil skeletons are in exceptional condition

Scientists discovered the fossil in the Liaoning Province of China in 2012. That region holds a reputation for its well-preserved fossils. Both the Repenomamus and the Psittacosaurus skeletons are nearly complete. This is a rarity that can be attributed to the conditions of the Liujitun fossil beds.

Often referred to as “China’s Dinosaur Pompeii,” this region is known for fossils of dinosaurs, small mammals, lizards, and amphibians. Volcanic eruptions triggered mudslides and debris that suddenly buried these animals.

The volcanic material present in the rock matrix contributes to the remarkable preservation of the fossil pair. Dr. Aaron Lussier confirmed the exceptional condition of the fossil. He is a mineralogist with the Canadian Museum of Nature.

Study co-author Dr. Gang Han originally cared for the Psittacosaurus-Repenomamus fossil in China. He brought it to the attention of palaeobiologist Xiao-Chun Wu at the Canadian Museum of Nature.

A close examination of the fossil reveals the larger dinosaur lying prone, its hind limbs folded on either side of its body. Above it, the body of the mammal attacking the dinosaur coils to the right. Repenomamus is seen gripping the jaw of the larger dinosaur and biting into its ribs.

“The weight of the evidence suggests that an active attack was underway,” declares Dr. Mallon. The researchers are confident that this wasn’t a case of a mammal scavenging a dead dinosaur. For one, there were no tooth marks on the dinosaur’s bones, a strong indicator of an active prey, not a scavenged one.

Similarities found in the present day animal kingdom

The findings from this study draw parallels to present-day predator-prey relationships. Smaller animals today, like wolverines, wild dogs, jackals, and hyenas, are known to hunt larger animals.

Mallon explains, “This might be the case of what’s depicted in the fossil, with the Repenomamus actually eating the Psittacosaurus while it was still alive — before both were killed in the roily aftermath.”

This discovery, while significant, is likely just the tip of the iceberg. The research team posits that the Lujiatun fossil beds in China, known for their volcanically derived deposits, will continue to offer new evidence of species interactions. These incredible discoveries paint a more nuanced picture of life during the Cretaceous period.

More about Psittacosaurus

Psittacosaurus, a name that translates to “parrot lizard,” was a genus of ceratopsian dinosaur that lived during the Early Cretaceous period, approximately 125 to 100 million years ago.

Here’s what we know about this intriguing dinosaur:

Physical characteristics

Psittacosaurus was a relatively small dinosaur. They ranged in size from the smallest species at roughly 1 meter (3.3 feet) in length to the largest species at about 2 meters (6.6 feet) in length. Unlike their more well-known relative, Triceratops, early ceratopsians like Psittacosaurus did not have large horns or frills.

Psittacosaurus is noted for its distinctive skull, which had a parrot-like beak, giving it its name. It had teeth adapted for shearing and slicing. Psittacosaurus also had self-sharpening cheek teeth, much like those of modern herbivorous mammals.

Diet and behavior of Psittacosaurus

Psittacosaurus was a herbivore, feeding mostly on vegetation. Its strong jaw muscles and distinctive beak perfectly suited Psittacosaurus for nipping off leaves and other plant matter.

Fossil evidence suggests that these dinosaurs lived in herds. Living in groups might have provided some defense against predators, which would have included small theropods.

Distribution and discovery

Archaeologists have found fossils of Psittacosaurus across a wide range of Asia, including China, Mongolia, Siberia, and possibly Thailand. The sheer number and geographical spread of Psittacosaurus fossils make it one of the most extensively studied dinosaurs.

Variation among species

Psittacosaurus is a very diverse dinosaur genus, with more than a dozen species named. This variation isn’t just in size. Different species also exhibit differences in features such as the shape of the skull and the number and placement of teeth.

Notable discovery shows that mammals attacked dinosaurs

Some particularly well-preserved fossils of Psittacosaurus have allowed for exceptional insights into the dinosaur’s biology. One notable specimen, described in 2020, preserved not only the dinosaur’s skin and pigmentation but also the contents of its stomach. This allowed researchers to determine that it had a diet of ferns, conifers, and other plants.

Another Psittacosaurus fossil unearthed in China is unique for the evidence of predation it shows. This is the fossil referred to above, in which a Psittacosaurus is found entwined with a mammal, Repenomamus. As previously stated, the discovery suggests that it was being preyed upon by this creature. This evidence proves contrary to the usual conception of dinosaur-mammal dynamics at that time.

Growth and development

The extensive fossil record of Psittacosaurus, which includes many juvenile specimens, has also allowed scientists to study how these dinosaurs grew and developed. The evidence suggests that Psittacosaurus grew rapidly during their early years, much like birds and mammals. Compared to other reptiles, this is unusual. They also appear to have had a long lifespan compared to other dinosaurs of similar size.

In summary, due to its extensive fossil record, researchers have studied Psittacosaurus extensively. It provides us with important insights into dinosaur evolution, behavior, and ecology during the Early Cretaceous period.

More about Repenomamus robustus

Repenomamus robustus is an extinct mammal species that lived during the Cretaceous period, around 130 to 125 million years ago. The fossil record, primarily found in China, provides most of our knowledge about it.

The Repenomamus genus to which it belongs includes some of the largest known mammals of the Mesozoic era, a time when most mammals were small and typically the size of rodents or smaller.

Here’s what we know about this intriguing creature:

Physical characteristics

Repenomamus robustus was a relatively large mammal for its time, measuring about 1 meter (3.3 feet) in length. This is about the size of a modern-day badger or raccoon. The animal was heavily built with a robust skeleton, which is reflected in its name “robustus.”

Diet and behavior of Repenomamus

Repenomamus robustus was carnivorous, as indicated by its strong jaws and sharp teeth. It’s one of the few mammals known from the Mesozoic era that are thought to have been capable of preying on small dinosaurs.

In addition, the recently discovered fossil of a Psittacosaurus and Repenomamus entwined in what appears to be a predator-prey relationship further highlights the animal’s capability to hunt and attack dinosaurs. This discovery challenges the view that mammals were predominantly small and preyed upon during the dinosaur-dominated Mesozoic era.

Paleontological significance of Repenomamus

Repenomamus robustus and its relative, Repenomamus giganticus, are significant because they provide evidence that mammals were not just passive players in the age of dinosaurs.

At least some mammals, like Repenomamus, were active predators. They could take on other animals of their time, including small dinosaurs.

These creatures help to fill in our understanding of the Cretaceous period’s ecology and the range of niches that mammals could occupy. They also help to demonstrate that the evolution of mammals and their roles in ecosystems were more complex than previously thought.

Repenomamus robustus provides us with a fascinating glimpse into the diversity of life during the Mesozoic era. Despite living in a world dominated by dinosaurs, these mammals were able to carve out their own niche.

Often times, they even turned the tables on their reptilian contemporaries. This fact significantly adds to our understanding of this period’s biodiversity.

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