- Adalatherium hui, which in Malagasy and Greek translates into “crazy beast,” was discovered from the study of a 66 million-year-old fossil from Madagascar.
- An early mammal species, it has a peculiar anatomy and a mosaic of features that is distinct from other mammals, from its peculiar teeth to its curved leg bones.
- It is also unusually large, the size of a house cat, compared to other mammals that coexisted with dinosaurs, which were no bigger than present-day mice.
- The researchers believe it is key to understanding the early evolution of mammals in the southern hemisphere.
A 66-million-year-old fossil has allowed scientists to describe a bizarre new species of mammal that lived in Madagascar during the time of the dinosaurs. They’ve christened it Adalatherium hui, which in Malagasy and Greek translates into “crazy beast.” The “hui” is a nod to Yaoming Hu, a paleontologist who specialized in early mammals.
To the lay eye, it looks like a house-cat-sized badger; but to the scientists who discovered it, A. hui is nothing short of the “oddest of oddball” creatures. “Knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal-like Adalatherium could have evolved; it bends and even breaks a lot of rules,” lead researcher David Krause, curator at the Denver Museum of Nature & Science, said in a statement.
The fossil record is sparsely populated with mammalian fossils from the Mesozoic era. The team got lucky and discovered a well–preserved, almost complete, skeleton in northwestern Madagascar. It turned out to be the most complete fossil of any Mesozoic mammal found from the southern hemisphere. The Mesozoic, known as the age of the dinosaurs, lasted from about 252 million years ago to about 66 million years ago.
What makes the creature exceptional is its anatomical structure, which is a unique mosaic of features. For one thing, its peculiar teeth give very little indication of its ancestry because they are nothing like those found in other mammals. For another, its vertebral column has more vertebrae that any of contemporaneous mammals. Then, there are the strangely curved leg bones.
“Trying to figure out how it moved is nearly impossible because, for instance, its front end is telling us a different story than its back end,” said Simone Hoffmann of the New York Institute of Technology, a co-author of the study.
It is also unusually large compared to other mammals that coexisted with dinosaurs, which were no larger than present-day mice.
The discovery of animals and plants of odd sizes is not unusual for islands. A. hui is a member of gondwanatherians, a poorly understood group of extinct mammals that lived on the supercontinent of Gondwana. On this massive landmass, Madagascar lay sandwiched between what would later become Africa and the Indian subcontinent.
Madagascar separated from the Indian plate about 88 million years ago and thus became the oldest island on the planet. The wild inhabitants of Madagascar have evolved in isolation for millions of years, which explains the bizarreness of many of the species found here. The branch of mammals that gave rise to A. hui evolved unhindered for more than 20 million years on the island.
“Long isolated places produce very unique results in biology,” Guillermo Rougier, a paleontologist at the University of Louisville and co-author of the paper, said in a release. “These fossils keep reminding us of the unexpected forms and shapes that evolution can take over long periods of time in an isolated place.”
A. hui is only the latest addition to the pantheon of strange species that live and have lived in Madagascar. The island is home to a who’s who of the world’s weirdest creatures. Krause and his team alone have uncovered several: from an armored predatory frog (Beelzebufo ampinga) the size of a beach ball, to a type of pug-nosed, vegetarian crocodile (Simosuchus spp.), and even a buck-toothed dinosaur (Masiakasaurus spp.).
The team puzzled over the A. hui specimen for more than a decade, trying to place it in the mammalian evolutionary history. They say they believe it is key to understanding the early evolution of mammals in the southern hemisphere. However, very little is known about the other fauna that existed at the dawn of the rise of mammals. The discovery of more strange species should give a clearer picture of early mammalian evolution.
The research was funded by the National Science Foundation and the National Geographic Society, and the paper published April 29 in the journal Nature.
Citation:
Krause, D. W., Hoffmann, S., Hu, Y., Wible, J. R., Rougier, G. W., Kirk, E. C., … Rahantarisoa, L. J. (2020). Skeleton of a Cretaceous mammal from Madagascar reflects long-term insularity. Nature. doi:10.1038/s41586-020-2234-8
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(Banner Image: A life-like reconstruction of Adalatherium hui. Image Courtesy: Denver Museum of Nature & Science/Andrey Atuchin)
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