Repenomamus

The Repenomamus was discovered in the year 2000. Its name, in Latin, means “reptile mammal.“

Classification

Repenomamus is a genus of two species, namely Repenomamus robustus and Repenomamus giganticus. The latter was one of the biggest mammals in the Mesozoic era (252-66 million years ago), the last of the three eras of the Cretaceous period (Triassic, Jurassic, Mesozoic).

Repenomamus is a genus of triconodonts, a group of early mammals with no modern relatives. This ancient mammal was in the now extinct Clade Eutriconodonta (once known as Triconodonta), which existed in Asia, Africa, Europe, and North and South America.

It is also a member of the extinct Family Repenomamidae. The two species of Repenomanus are the sole members of the Repenomamidae Family; however, they are sometimes listed as members of the Family Gobiconodontidae because there is also a close relationship to this family. Only the discoveries of more fossils and further research will determine the actual family.

Description and Size

From the fossils that were found of this ancient mammal, the following attributes could be aggregated to describe its physical features:

• The Repenomamus giganticus was about 3 feet and 3 inches long and weighed between 26-31 pounds.
• The Repenomamus robustus was about half the size of the giganticus, and it weighed around 8.8-13 pounds; it compares to the size of an opossum.
• Repenomamus had a strong jaw that held sharp and pointy teeth in the front for biting into the flesh, but it also had a few chewing teeth that aroused the suspicion that it may have been a predator more than a scavenger. 
• The Repenomamus also had a few whiskers on its face. They were long, sensitive, and resembled the whiskers of a cat today. 
• Resembling a badger or a large cat, it had a heavy body that was covered in a coat of fur. Its body was far bulkier and larger than its limbs. 
• It also had a short tail that was covered in fur. 
• It had two pairs of strong and short legs and walked on its broader feet like a badger. However, the plantigrade feet indicated that it sprawled and ran on the ground. Each foot had several claws also.

Diet

Considering its fossils and sharp, pointy teeth, it is safe to assume that the Repenomamus was a carnivore. However, the scientists were divided as to whether the mammal was a predator or a scavenger. 

The common idea was that this mammal ate small dinosaurs. Others believed that it also ate insects and various smaller creatures. But, an important fossil finding indicated its true diet. 

The Repenomamus fossil was found with bones in its gut contents of another small dinosaur that itself was a plant-eater. This strongly supports the idea that it ate small dinosaurs. So, the theory it was a predator is more concrete than the chance it was a scavenger. 

Most of the mammals at the time were considered scavengers. Various fossils of other dinosaurs had bite marks of the smaller mammals showing that the mammals lurked in the shadows and feasted on the dinosaur carcasses.

Habitat

Studies suggest that the Repenomamus lived in shallow areas and lurked in the shadows, like a scavenger. It made its home in similar areas but did not stay much under the shadows. The fossil of this mammal was found in Northeastern China. This part of China is known to have been home to feathered dinosaurs. Whether it was a common ground for both of them is unknown.  

Behavior 

Considering the diet of Repenomamus, it can be assumed that it hunted in packs. Because the Repenomamus was one of the first mammals that might have eaten dinosaurs, it is believed that they were sociable and grouped together to hunt for their prey. Other mammals of the same era were mainly insectivorous. Most of the mammals during this time spent time in shallow areas, hiding from the dinosaurs.

How did the Repenomamus become so ferocious in nature? The existing theory suggests that Repenomamus was living in a different place than these other mammals. According to the fossils, Repenomamus lived amongst feathered dinosaurs. It did not have to hide because there were no larger predators scaring it away. Accordingly, its prey were small dinosaurs.

Threats And Predators

There are no known predators of the Repenomamus. But similar to other mammals, they were threatened by the nature and habitat of that era. 

In the Cretaceous era, things like land fragmentation, hunting, habitat modification, land degradation, and deforestation were quite common. In addition, the Repenomamus was known to be a hunter of small dinosaurs. It was probably not living in shallow areas like other mammals that were insectivores. This leads us to believe that any bigger dinosaur may have been a threat to the Repenomamus, along with natural disasters. 

Discoveries and Fossils

The Repenomamus does not have many fossils around the world. The only thing known is that this genus has two known species and both of them were found in China. As discussed above, they are Repenomamus robustus and Repenomamus giganticus.

In 2000, the first fossil of Repenomamus was discovered in the northeastern side of China, specifically in the Liaoning province. The Repenomamus robustus species was discovered first, then Repenomamus giganticus was found in the year 2005. The fossils of both species date to the early Cretaceous period, about 125-123.2 million years ago. 

The fossil of the Repenomamus giganticus is one of the largest mammal fossils to have been found. However, the fossil of Repenomamus robustus provided some interesting insight, offering potential evidence that this mammal ate other, small dinosaurs because its skeleton was found with the skeleton of a baby dinosaur of a different species. 

Extinction

The exact cause is unknown, but the basic assumption is that the Repenomamus died when a meteorite hit the Earth 66 million years ago. This great Extinction Event wiped out three-fourths of the animal population, including almost all the dinosaurs.

Similar Animals to The Repenomamus 

• Tasmanian Devil – The Repenomamus seems a lot like the modern Tasmanian Devil. It has a similar size and body shape, and it even hunts in a similar scavenger fashion. Its ferocious nature also somewhat takes the nature of the Repenomamus.