New “reaper of death” tyrannosaur discovered in Canada.

National Geographic revels in the grisly remains of a killer found in a museum cabinet – bones that turned out to belong to a prehistoric predator that’s revealing a lot about how tyrannosaurs came to be:

Aged roughly 79.5 million years, Thanatotheristes degrootorum sits near the base of the tyrannosaurs’ ascent to ecological domination. The unearthed skull fragments—including upper and lower jawbones, teeth, and a partial cheekbone—sketch out the early pages of how tyrannosaurids, the tyrannosaur subgroup that includes T. rex, rose to power and became top predators.

“I tried to be really meticulous with identifying features that made it unique,” says [Jared] Voris, who is now a Ph.D. student at the University of Calgary. “It’s interesting to have the opportunity to name a new species—and I’m hoping it isn’t all downhill from here.”

About 80 million years ago, these other predators faded away, giving tyrannosaurs a chance to rise to the top of the food chain and grow into giants. By 66 million years ago right before its extinction, the infamous T. rex grew up to 40 feet long and weighed more than nine tons. But Thanatotheristes, unveiled in Cretaceous Research on January 23, doesn’t seem to have been as large or as hulking as T. rex, underscoring the diversity at the top of this period’s food chain.

John and Sandra De Groot stumbled on the bones in 2010, as their family walked along the shoreline of southern Alberta’s Bow River. The pair contacted the Royal Tyrrell Museum, which sent paleontologists to collect the fossils and search for more. To honor the family, Voris’ team gave Thanatotheristes the species name degrootorum.

“They’ve been an invaluable resource,” Voris says of the De Groots. “It just shows, you don’t have to be a paleontologist to help out in paleontology.”

Nearly a decade after the fossils were cleaned, catalogued, and stored, Voris and his colleagues began putting the paleo-puzzle together. The team focused on the jawbones, which had uniquely prominent ridges that hinted at long-lost facial structures. The animal’s cheekbone also had an oval shape in cross-section, unlike other closely related tyrannosaurids.

[via TravMedia]