Evolution is often an unpredictable cocktail of happy accidents, environmental anomalies, and that just-right blend of genetic material assembling in fortuitous order.So it's nosurprise thatpaleontologists are somewhatbaffled by a new species of creaturethey've officially namedAdalatherium hui,which, as translated fromMalagasy and Greek,means "crazy beast."
But more than just a weird 66-million-year-old mammal that lived during the Age of the Dinosaur when the mighty T-rex reigned supreme, Adalatherium is a vital componentofthe complicatedmystery ofearly mammalian evolution in the Southern Hemisphere.
As detailed in a new studypublished last weekin theJournal of Vertebrate Paleontology, a14-member team of international researchers headed upby Dr. David Krauseof the Denver Museum of Nature & Scienceand Dr. Simone Hoffmann of the New York Institute of Technologydescribed their intensive analysis of the odd, opossum-sized animal that existed nearthe end of the Cretaceous periodon the island of Madagascar.
These new revelations delvedeep into the evolutionary history of mammals from the prehistoric supercontinent of Gondwana known currentlyas Africa, South America, Australia, Antarctica, the Indian subcontinent, and the Arabian Peninsula.
Adalatherium is part of an extinct collectionof early mammals catalogued asgondwanatherians, which were initially unearthedbackin the 1980s, butthen known onlyby a scattering ofteeth and jaw fragments.
For this latest study, research on this unusualanimal was carried out over a 20-year stretch using its perfectly preserved fossilzed remainsthat representthe most complete skeleton for any mammal discovered so far in the Southern Hemisphere before the dinosaurs became extinct.Adalatherium appears to be a jumbo-sizedrelative to the shrew-like, or mouse-ishmammals that thrived in that primeval environment.
In addition to the fact that Adalatherium was born withmore trunk vertebrae than most other mammals, its thickhind limbs were arrangedin asprawling position like today's crocodiles or lizards.These powerful back legs were paired withbulky,sprinting front legs tucked beneaththe torso, identical to most mammals seen in modern times.
It also sported rabbit-like front teeth coupled with a set of back teeth never observed in any other known mammal,living or extinct, as well asa sizableholein the bones at the crownof itssnout.
"Knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal likeAdalatheriumcould have evolved; it bends and even breaks a lot of rules," Krause explains. "Islands are the stuff of weirdness,and there was therefore ample time forAdalatheriumto develop its many extraordinarily peculiar features in isolation."
Sure, when seen in these detailed, life-like reconstructionsby renowned paleoartist Andrey Atuchin, it seems like a typical badger, but under its familiar-looking skin is an evolutionary puzzlement forthe ages.
"Adalatheriumis simply odd," notes Hoffman."Trying to figure out how it moved, for instance, was challenging because its front end is telling us a completely different story than its back end. Adalatheriumis an important piece in a very large puzzle on early mammalian evolution in the Southern Hemisphere, one in which most of the other pieces are still missing."
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