The
ancient mammal Adalatherium hui is so weird that it eluded
classification for over a decade.

A
roughly 70-million-year-old skeleton of the species, uncovered in Madagascar in
1999, was clearly a mammal. But it boasted several distinctly un-mammalian
features, such as a large hole on top of its snout. Also, although the animal’s
forelimbs were aligned with its spine, like a typical mammal, its back legs were
splayed out to the sides like a reptile.

“It is
so strange, compared to any other mammal, living or extinct,” says
paleontologist David Krause, of the Denver Museum of Nature & Science, “it
was just crazy.” Hence the name Adalatherium hui, from a Malagasy word
meaning “crazy” and the Greek word for “beast.”

Now, the
crazy beast finally has been identified as a gondwanatherian — an obscure group of mammals that
roamed the Southern Hemisphere during the age of dinosaurs, Krause and
colleagues report online April 29 in Nature. The key to the animal’s
identity was in comparing the skeleton to an intact skull from a different
gondwanatherian species, discovered in 2014 also in Madagascar. The arrangement of bones in
the snout of the skull
matched that of Adalatherium hui, establishing the animals as relatives.

Adalatherium hui fossil
Judging by this fossilized skeleton of Adalatherium hui, “we think it was probably a digging animal, much like a badger,” says paleontologist David Krause of the Denver Museum of Nature & Science. Badgers spread their hind legs and use their front legs to shoot dirt between them. The splayed hind legs of Adalatherium hui might be good for that. What’s more, Krause says, “badgers have these tiny little stubby tails so it doesn’t get in the way of the dirt flying backward, and Adalatherium hui also has a short, stubby tail.”Marylou Stewart

Placing Adalatherium
hui
among the gondwanatherians gives new insight into how this enigmatic
group of animals fit into the mammal family tree. Up to 2014, the only other known
traces of gondwanatherians were a handful of teeth and jaws. Given the
historically sparse fossil record for gondwanatherians, “we knew very little
about their anatomy,” and therefore how they were related to other ancient
animals, Krause says.

But the
features of Adalatherium hui’s nearly complete skeleton reveal that it was
closely related to a group of mammals called multituberculates, which lived in the Northern
Hemisphere during the age of the dinosaurs (SN: 12/14/96). “It’s almost
like we have a southern counterpart to the multituberculates” in the
gondwanatherians, he says.

Try
saying that 10 times fast.