Islands are the epitome of isolated evolution and Madagascar holds the crown for producing phenomenal plants and animals from hissing cockroaches to panther chameleons. It is the 4th largest island on earth and is where this 66 million-year-old, opossum-sized mammal fossil was found.
On 29th of April 2020, the journal Nature announced that a research team which was led by Dr. David Krause has discovered this perfectly preserved, not to mention practically complete skeleton in Madagascar. This new Mesozoic mammal was named Adalatherium which means “crazy beast’’, the name being derived from Malagasy and Greek languages.
Dr. Krause who is the Senior curator of vertebrate palaeontology at the Denver Museum of Nature & Science says that, compared to known mammals’ skeletal anatomies, it is astonishing how an ancient mammal like this managed to evolve. According to him, it is an inconceivable discovery which even breaks prevailing theories of palaeontology.
Gondwanatheria is an extinct group of Mammals which were previously recognised from cranial fragments, teeth and a few lower jaws. These mammals lived in the Southern Hemisphere in the ancient supercontinent Gondwana, hence the name. The first fossils were discovered in the 1980s in Argentina, and other fossils were found later in other countries including Africa, India, Madagascar and Antarctic Peninsula. These mammals were assumed to be similar to Armadillos, Anteaters and Sloths.
However, according to Dr. Krause, Gondwanatheria was a failed evolutionary experiment which came to an end during the Eocene. Adalatherium belongs to these mammals that went extinct approximately 45 million years ago. This mammal, which lived among dinosaurs and mammoth crocodiles, had bizarre nerves and blood vessel supply passageways. No living nor extinct mammal had this many of holes or (foramina) on its face – its most distinguished feature is the large hole which is located on top of its ultra-sensitive snout which was covered in whiskers. The teeth of Adalatherium also had peculiar traits compared to other mammals, one of the leg bones was curved in an abnormal way and its backbone had several more vertebrae than previous Mesozoic mammals that have been unearthed.
Its other pre-eminent quality is that Adalatherium was rather large as the other mammals who lived among the dinosaurs were usually the size of a mouse. The scientific team is still baffled by the bizarre features of Adalatherium. For one, according to Simone Hoffmann from the New York Institute of Technology who is the primary collaborator of Dr. Krause, Adalatherium’s anatomy tells two different stories from its front and back, making it quite tricky to figure out its movements other than presuming it was capable of running and digging.
Adalatherium’s extraordinary traits were developed as a result of the isolation of Madagascar from the mainland being alienated in the Indian Ocean. As the plate tectonic history of Gondwana evidence suggests, this isolation helped these mammals to evolve for over 20 million years.
Over the past 25 years Dr. Krause and his team have managed to uncover other vertebrates including a predatory frog (Beelzebufo), a buck-toothed dinosaur (Masiakasaurus) and a pug-nosed, vegetarian crocodile (Simosuchus) on Madagascar.
Even though Adalatherium is just a small piece of a puzzle in the long history of early mammalian evolution, it unfolds many new opportunities to further understand the lives of Gondwanatherians.
(by Learn for Pleasure on 4th May 2020)