A “crazy beast” that lived among the dinosaurs 1:47
(CNN) – Researchers have discovered the fossil of a primitive mammal called the “mad beast” that lived 66 million years ago alongside giant dinosaurs and crocodiles in Madagascar, and is unlike any known mammal, alive or extinct.
This mammal, the size of a possum, had a mixture of strange characteristics that had not been seen together before. It highlights the evolutionary strangeness that can arise when evolution occurs in isolation on islands like Madagascar, which is home to other species, living and extinct, found nowhere else in the world.
An initial study describing the “mad beast” discovery published in April in the journal Nature. That post was followed by a special issue of the Vertebrate Paleontology Society memoir series released on Friday.
The mammal is the most complete and best-preserved skeleton of a gondwanatherian, which is a mammal that lived on the ancient southern supercontinent Gondwana, which are now the continents of the southern hemisphere.
Fossils from the Mesozoic era, between 65 million and 252 million years ago, are rare from Gondwana, and largely include elements such as a single skull, chunks of jaw and teeth.
But this mammal, which looks a bit like a badger in the artist’s skeleton-based rendering, is so well preserved that it includes cartilaginous tissue, small bones, and the creature’s short tail.
The researchers called it Adalatherium hui, a hybrid name that combines the Malagasy word for “madman” and the Greek word for “beast.” Hui is a nod to the late Yaoming Hu, a co-author of the study at Stony Brook University.
They believe this particular creature was young, weighing around 3.5 kilos. But compared to the other Gondwanan mammals living at the time, which were the size of a mouse, it was quite large. And it lived among ancient dinosaurs and crocodiles before the asteroid impact wiped them all out 66 million years ago at the end of the Cretaceous period.
An incredibly strange animal
‘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, ”said David Krause, lead author of the study and senior curator of vertebrate paleontology at the Denver Museum of Nature and Science and professor emeritus at Stony Brook University, in a press call in April.
The skeleton contains a number of strange features that researchers cannot decipher.
For example, Adalatherium had more holes in its face than any known mammal, Krause said. These holes, called foramen, created pathways for blood vessels and nerves, leading to an incredibly sensitive snout that was covered in whiskers. It also had a large hole in the upper part of the snout that cannot be compared to any known mammal that has lived or is currently living.
Your teeth cannot be compared to anything else either. They are structured in a strange way that cannot be explained. Krause said his back teeth “are from outer space.”
The animal’s spine contained more vertebrae than any known mammal from the Mesozoic era. And he must have walked in a strange way, because the front half of the animal does not match the rear half. And one of its hind legs was bowed.
The forearms and shoulders can be compared to cats and dogs, meaning they were placed under the body, something very unusual for early mammals that walked more like reptiles, said Simone Hoffmann, a co-author of the study and an assistant professor at the New York Institute of Technology Department of Anthropology.
But the hind legs have the opposite pattern, suggesting that the legs are spread out and have more knee joints like reptiles. Two patterns on an animal mean that it walked very differently from anything that lived today, Hoffman said. But they believe he was capable of running, in addition to other ways of moving.
Adalatherium also had long, strong claws on its hind legs, suggesting that it dug using its hind legs.
“Adalatherium is the strangest of the weirdos,” Hoffmann said. “Trying to figure out how it moved is almost impossible because, for example, its front part tells us a different story than its rear.”
Strange island animals and where to find them
Krause and his colleagues have been researching fossils that belonged to unusual animals that lived in ancient Madagascar for 25 years. This fossil was found in 1999 at the site of a sedimentary basin in northwestern Madagascar. But it was recently investigated.
Multiple expeditions to that basin have revealed bones of dinosaurs and other vertebrates well preserved and buried by the ancient debris flow in the basin. But they had to collect thousands of specimens just to find a handful of mammalian fossils, Krause said.
In 2010, they found the skull of a gondwanatherian. Before that, his discoveries were largely limited to teeth and jaw fragments.
Fossils of a gondwanatherian were first found in Argentina, followed by discoveries in Africa, India, the Antarctic Peninsula, and Madagascar. At first, researchers believed they were related to sloths, anteaters, and armadillos. But they stand by themselves, unrelated to anything alive today, “now it is known that they were part of a great evolutionary experiment, doing their thing, an experiment that failed and became extinct [la época del] Eocene, about 45 million years ago, ”said Krause.
If the “mad beast” can be related to anything, it is multituberculates, a group of extinct rodent-like mammals that lived on the northern continents, according to the researchers.
Researchers attribute it to evolution in the isolated environment of an island. And Madagascar has been an island for a long time. It separated from the Indian subcontinent 88 million years ago and has been alone ever since.
This allowed Madagascar animals and dinosaurs like Adalatherium “enough time to develop their many ridiculous characteristics,” Krause said.
Krause’s team has found other bizarre fossils in Madagascar, including a giant, armored predatory frog named Beelzebufo, a short-nosed herbivorous crocodile named Simosuchus, and a deer-tooth dinosaur named Masiakasaurus.
“Madagascar is a pretty strange place,” Krause said. Plants and animals are not known anywhere else in the world. Evolution on the islands leads to that in a sense. ‘
When animals evolve in isolated areas, such as islands, they face more competition, both in predators and in food sources. This causes them to grow into species that do not resemble the animals of the continent, including unusual shapes and sizes.
Researchers call it the “island rule”: Small animals increase in size, a form of gigantism, while large mammals decrease in size.
Adalatherium probably disappeared along with the rest of the strange animals in Madagascar 66 million years ago, before the island’s population started again with native species such as lemurs. But the discovery sheds information about the fascinating mammals that came before the ones we know today. And only more research and discovery will fill the remaining gaps.
“Adalatherium is only one piece, but an important piece, in a great puzzle about the early evolution of mammals in the southern hemisphere,” Krause noted. “Unfortunately, most of the pieces are still missing.”