Meet the crazy beast that lived among dinosaurs

A strange 66 million year old mammal described in new research offers insightful new insights into the evolutionary history of mammals on the supercontinent of Gondwana.

Called Adalatherium, which translated from Malagasy and Greek means “mad beast”, it is described on the basis of an almost complete and beautifully preserved skeleton, the most complete for any mammal discovered so far in the Southern Hemisphere before the extinction of the dinosaurs.

Research now published in the Journal of Vertebrate Paleontology and conducted for 20 years shows that Adalatherium was a ‘giant’ in relation to the mammals, usually the size of a shrew or mouse, that lived during the period. Chalk.

Its ‘weird’ features included more trunk vertebrae than most other mammals, muscular back legs placed in a more outstretched position (similar to modern crocodiles) along with fast, muscular front legs tucked under the body (as seen in most mammals nowadays), front teeth like those of a rabbit and rear teeth completely different from any other known mammal, living or extinct, and a strange opening in the bones in the upper part of the snout.

A team of 14 international researchers led by Dr. David Krause (Denver Museum of Nature and Science) and Dr. Simone Hoffmann (New York Institute of Technology) published the full description and analysis of this one-size mammal. opossum that lived among dinosaurs and huge crocodiles towards the end of the Cretaceous (145-66 million years ago) in Madagascar. The first announcement of the discovery was made earlier this year in the journal Nature.

Native to Madagascar, Adalatherium belongs to an extinct group of mammals known as gondwanatherians, first discovered in the 1980s and until recently represented only by a few isolated teeth and jaw fragments. But even those scant remains indicated that Gondwanaten were very different from other modern mammals. There were so many mysteries surrounding the Gondwanatherians that it was unclear how they fit into the mammal family tree.

Now the research team is presenting the first skeleton of this mysterious group to ever roam much of South America, Africa, Madagascar, the Indian subcontinent and even Antarctica.

The integrity and excellent preservation of the Adalatherium skeleton opens new windows of what the Gondwanatherians were like and how they lived, but its strange features still baffled the team.

“Knowing what we know about the skeletal anatomy of all living and extinct mammals, it is hard to imagine that a mammal like Adalatherium could have evolved; it questions and even breaks many rules, ”Krause explains.

Although the realistic reconstruction of Adalatherium superficially resembles that of a common badger, the “normality” is only superficial. Below the surface, his skeleton is nothing short of extravagant.

As Hoffmann puts it, “Adalatherium is just weird. For example, it was a challenge to find out how it moved, because the interface tells us a very different story than the one on its back ”.

While its muscular back legs and large claws on its back legs may indicate that Adalatherium was a powerful burrower (like badgers), its front legs were less muscular and more like those of living mammals that can run fast.

The Adalatherium limbs also indicate that its posture was a hybrid between that of living mammals and older relatives. The front legs were hidden under the body (as seen in most mammals today), but the rear legs were more elaborate (such as in crocodiles and lizards).

Reconstructed by high-resolution microcomputer tomography and extensive digital models, Adalatherium teeth are indicative of herbivory, but otherwise more than bizarre.

Not only did Adalatherium have ever-growing front teeth, similar to those of a rabbit or rodent, but its rear teeth are completely different from those of any other known mammal, living or extinct. If only these teeth had been found, the mystery of what this animal was probably wouldn’t have been solved! In addition to the apparent chaos, there is a hole in the upper part of the muzzle for which there is simply no parallel.

The Adalatherium, about the size of a Virginia opossum, was very large at the time. Although not particularly large by today’s standards, it was a giant compared to the shrew and mouse-sized mammals that lived in the Cretaceous Period.

Gondwana’s geological history provides clues as to why Adalatherium is so strange.

Adalatherium was found in rocks that date back to the end of the Cretaceous, about 66 million years ago. At the time, Madagascar had been an island separate from Africa for over 150 million years and from the Indian subcontinent for over 20 million years. “Islands are bizarre,” says Krause, “so there was ample time for Adalatherium to develop its many extraordinarily peculiar properties individually.”