FIVE THINGS ABOUT HOW F EROCIOUS CARNIVOROUS DINOSAURS GREW

Large meat- eating dinosaurs attained their great size through very different growth strategies, with some taking a slow and steady path and others experiencing an adolescent growth spurt. Here’s some new detail that has emerged from recent research.

1 SIXTY- SOME MILLION YEARS AGO

Scientists analyzed annual growth rings of fossilized bones from museums in the U.S., Canada, China and Argentina and even received clearance to cut into bones from one of the world’s most famous Tyrannosaurus rex fossils, known as Sue and housed at the Field Museum in Chicago.

2 LIKE OUR TEENS TODAY

Sue’s leg bones helped illustrate that T. rex and its relatives, the tyrannosaurs, experienced a period of extreme growth during adolescence and reached full size by around age 20. Sue, measuring about 13 metres, inhabited South Dakota about a million years before all the dinosaurs were wiped out by an asteroid impact 66 million years ago.

3 SAME FAMILY, DIFFERENT GROWTH

Other groups of large theropods (carnivores with two powerful hind legs and short forelegs) tended to have more steady rates of growth over a longer period. That growth strategy was detected in lineages in the southern continents, such as Allosaurus and Acrocanthosaurus from North America and Cryolophosaurus from Antarctica.

4 LONG GROWING PAINS

A recently discovered species from Argentina that rivalled T. rex in size and is one of two species in a group called carcharodontosaurs did not reach full adult size until its 40s.

5 THE BONES KNOW

Big theropods share the same general body design, large skulls and menacing teeth. “Prior to our study, it was known that T. rex grew very quickly, but it was not clear if all theropod dinosaurs reached gigantic size in the same way,” said paleontologist and study lead author Tom Cullen of the North Carolina Museum of Natural Sciences.