Serendipitous Discovery

In the summer of 1999, an international team of researchers carved a chunk of earth out of the Mahajanga Basin in northwest Madagascar, jacketed it in plaster, and shipped it back to the United States. The region is flush with fossils dating back millions of years, and the scientists thought they had discovered the remains of an ancient crocodile. It wasn’t until years later, when the block was finally scanned, that they realized they had one of the most significant fossil discoveries in the early evolution of mammals on their hands.

“This particular block of sedimentary rock wasn’t an immediate priority because we didn’t know what was in it besides the small crocodile, and we had lots of fossil crocodiles,” says Raymond Rogers, DeWitt Wallace Professor and Geology Department chair. Rogers has been the lead geologist and one of the long-standing co-principal investigators on the 25-year project in Madagascar, which is funded by the National Science Foundation and the National Geographic Society.

Working with local researchers from the University of Antananarivo, the team has unearthed some amazing fossil animals over the last quarter-century, including a giant predatory frog (Beelzebufo) and a meat-eating, cannibalistic dinosaur (Majungasaurus). None of these earlier finds, however, compare to what the team described in an April article published in the scientific journal Nature.

The specimen is the most complete and well-preserved skeleton for any Mesozoic-era mammal yet discovered in the southern hemisphere. So complete, in fact, that Rogers and his colleagues were able to identify the animal’s exceptionally unusual features, including limbs that were adapted for both digging and running; numerous holes in the nasal region that indicate it likely had a very sensitive snout; and teeth unlike those known in any fossil or living mammal. “This strange mammal is without question the best-preserved specimen that we have yet discovered in the rocks of the Mahajanga Basin,” says Rogers, one of the article’s co-authors.

The team named the 66-million-year-old opossum-sized creature Adalatherium, which is translated from the Malagasy and Greek languages, and means “crazy beast.” Mammals, especially ones of this size, were rare during the Cretaceous Period, when dinosaurs ruled much of the earth.

“It’s very important because the fossil provides new insights into mammal morphology and evolution during the Mesozoic Era—a time when mammals were scurrying around at the feet of dinosaurs,” Rogers says.

In his role as lead geologist, Rogers focuses on the age of the rocks and fossils—the nature of the ancient ecosystem—and the ways that incredible fossils like this one get preserved, a field of study known as taphonomy. “This animal was likely buried alive and took a different path to the fossil record than its compatriots,” he says. “It has an epic death and burial story.”

The discovery of Adalatherium not only adds a crucial piece to the puzzle of what life on our planet was like millions of years ago, it joins the likes of penicillin and the X-ray in the distinguished annals of scientific breakthroughs that almost never happened. “There’s no magic to it. It’s not like we knew what was in the block when we dug it out,” Rogers says. “We just collected it for one fossil and we got two.”