66 million-year-old “Mad Beast” fossil discovered in Madagascar

In evolutionary terms, islands are rare things. It is on islands where animals evolve in isolation, often over millions of years, with different food sources, competitors, predators, and parasites … in fact, all different compared to the mainland species. As a result, they develop in different shapes and sizes and evolve into new species that, with enough time, generate even more new species.

Malagasy mammal of 66 million years

Such is the case with the discovery of a strange new 66 million year old mammal (coined the ‘crazy beast’) in Madagascar by a team of international researchers led by Dr. David Krause, chief curator of vertebrate paleontology in the Denver Museum. Nature & Science and Professor Emeritus at Stony Brook University, where part of the research was conducted.

The discovery of this opossum-sized mammal that lived among dinosaurs and massive crocodiles on the fourth largest island on Earth was announced today in the newspaper. Nature. Dr. James B. Rossie of Stony Brook University is one of the study’s co-authors. The late Yaoming Hu of Stony Brook University was also a co-author.

Realistic reconstruction of Adalatherium hui (“mad beast”), a new Late Cretaceous Gondwanatherian mammal from Madagascar. (Andrey Atuchin / Denver Museum of Nature and Science )

The discovery of the new mammal, called Adalatherium, which is translated from the Malagasy and Greek languages ​​and means “crazy beast”, it is based on an almost complete skeleton that is surprisingly well preserved. The skeleton is the most complete for any Mesozoic mammal discovered so far in the southern hemisphere.

The crazy beast had extravagant features

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

In fact, although a real reconstruction might lead us to think that Adalatherium he was an ordinary badger, his “normality” is literally only superficial. Beneath the surface, his skeleton is nothing less than “flamboyant”. It has primitive features in its snout region (like a septomaxilla bone) that had not been seen for a hundred million years in the lineage leading to modern mammals.

Skeletal reconstruction of Adalatherium hui (“crazy beast”). Lateral view based on computed tomography scans of individual elements. (Simone Hoffmann / Nature)

“Its nasal cavity exhibits a striking mosaic of features, some of which are very standard for a mammal, but others that I’ve never seen before in anything,” Rossie said.

Adalatherium it had more holes (holes) in its face than any known mammal, holes that served as passageways for nerves and blood vessels supplying a very sensitive muzzle that was covered in whiskers. And there is a very large hole at the top of its snout that is simply unparalleled in any known, living, or extinct mammal.

The teeth of Adalatherium they are very different in construction than any known mammal. Its spinal column had more vertebrae than any Mesozoic mammal, and one of its leg bones was curiously curved.

Reconstructed skeleton of Adalatherium hui (“crazy beast”) showing the many vertebrae of the species. (Scott Hartman / Nature)

About the size of a Virginia opossum, Adalatherium It was also unusual in that it was too big for its day; Most of the mammals that lived alongside the dinosaurs were much smaller, about the size of a mouse on average.

The late Gondwanatherian

Adalatherium It belongs to an extinct group of mammals called Gondwanatherians because they are only known from the ancient southern supercontinent of Gondwana. The Gondwanather fossils were first found in Argentina in the 1980s, but since then they have also been found in Africa, India, the Antarctic Peninsula, and Madagascar.

Gondwanatherians were first thought to be related to sloths, anteaters and modern armadillos, but “now it is known that they were part of a great evolutionary experiment, doing their own thing, an experiment that failed and became extinct in the Eocene, about 45 million years ago, “Krause explained.

Before the discovery of the almost complete skeleton of AdalatheriumGondwanatherians were only known from isolated teeth and jaw fragments, with the exception of a Madagascar skull described by Krause and his team in 2014.

The strangest of the oddballs

The integrity and excellent preservation of the skeleton of Adalatherium Potentially opens new windows on what the Gondwanatherians were like and how they lived, but the strange features have yet to be guessed by the science team.

As stated by Krause’s senior collaborator Simone Hoffmann of the New York Institute of Technology, ” Adalatherium It is the strangest of the oddballs. Trying to figure out how it moved is almost impossible because, for example, its front tells us a different story than its back. “The research team is still uncovering clues, but they think that although Adalatherium It could have been a powerful digging animal, it was also capable of running and potentially even had other forms of locomotion.

Gondwana’s plate tectonic history provides independent evidence of why Adalatherium it’s very strange Adalatherium It was found in rocks dated near the end of the Cretaceous, 66 million years ago. Madagascar, with the Indian subcontinent attached to the east, separated from Africa more than a hundred million years ago and was finally isolated as an island in the Indian Ocean when the Indian subcontinent separated approximately 88 million years ago and headed north . That left the lineage that ultimately resulted in Adalatherium evolve, isolated from continental populations, for more than 20 million years: “long enough to develop its many absurd characteristics,” Krause said.

Masoala National Park in modern Madagascar. ( Challenge / Adobe stock)

The fossil record of the earliest mammals in the northern hemisphere is approximately an order of magnitude better than that of the south.

Important piece of the puzzle, but only the beginning

“Adalatherium “It is just a piece, but an important piece, in a very big puzzle about the early evolution of mammals in the southern hemisphere,” said Krause. “Unfortunately, most of the pieces are still missing.”

More than anything, this discovery highlights to researchers how much remains to be learned by making new discoveries of the earliest mammals in Madagascar and other parts of ancient Gondwana.

In addition to Krause, Hoffmann, and Rossie, other researchers involved in the new discovery, which was funded by the National Science Foundation and the National Geographic Society, were: the late Yaoming Hu of Stony Brook University; John R. Wible of the Carnegie Museum of Natural History; William W. Rougier of the University of Louisville; E. Christopher Kirk of the University of Texas at Austin; Joseph R. Groenke of Stony Brook University and Ohio University; Raymond R. Rogers of Macalester College; Julia A. Schultz from the Institut für Geowissenschaften der Universität Bonn, Alistair R. Evans from Monash University and the Victoria Museums; Wighart von Koenigswald of the Institut für Geowissenschaften der Universität Bonn; and Lydia J. Rahantarisoa from the Université d’Antananarivo.

The new Adalatherium Mammal is just the latest in a series of strange boneless animals discovered by Krause and his research team in Madagascar in the past 25 years. Previous discoveries have included a giant, armored predatory frog ( Beelzebufo), a vegetarian pug-nosed crocodile ( Simosuchus) and a small dinosaur with rabbit teeth ( Masiakasaurus)

A lemur in Madagascar. ( guinevra / Adobe stock)

The island itself is full of animals (and plants) found nowhere else on the planet, including hissing cockroaches, giraffe weevils, tomato frogs, satanic leaf-tailed geckos, panther chameleons and striped tenrecs, to name a few. And of course there is the characteristic group of mammals, the lemurs, which became famous in the animated films “Madagascar”. Just a few thousand years ago, Madagascar’s fauna also included 1,400-pound elephant birds, gorilla-sized lemurs, and pygmy hippos.

Top image: fossil remains of the skeleton of Adalatherium hui or the “crazy beast”, which was unearthed in Madagascar. Source: (Marylou Stewart / Nature)

The article, originally titled “Marooned on Mesozoic Madagascar”, first appeared in Daily science Source: Stony Brook University dated 04/29/2020 and republished with permission.