Teen T-rex had monster growth spurt
Anna Gosline

18:00 11 August 04

Towering Tyrannosaurus rex reached its colossal proportions due to a monster
growth spurt in its teenage years, reveals a new study.

Once the world was stalked by giants, from the six-tonne flesh-eating T. rex
to Brachiosaurus, a lumbering vegetarian sauropod that weighed in at an
impressive 88 tonnes. But 65 million years after the dinosaurs disappeared,
relatively little is known about how they became so big.

Now, Gregory Erickson, a palaeontologist at Florida State University in
Tallahassee, US, has collected a large number of small, discarded T. rex
bones sitting in museum drawers, and found the bones contain a treasure
trove of well preserved growth rings inside. These cast-offs have allowed
Erickson and his colleagues to chart out the first growth curve for T. rex.

The team shows that T. rex became a giant only in its teenage years,
undergoing an exponential growth spurt for around four years during
adolescence.

It therefore achieved its gigantic size not by growing for longer, as do
modern mammals and lizards, but by growing dramatically faster. An
adolescent T. rex would have gained about 2 kilogrammes a day between the
ages of 14 and 18, before slowing down and settling into adulthood.

Live fast, die young

By using polarising light microscopes to examine bone growth rings, the team
was also able to age the skeletons of 20 different specimens, including the
famous Sue, on display at the Field Museum in Chicago, US.

Sue it emerges, is not only the largest T. rex known, but also the oldest.
But even she died at just 28. "T. rex lived fast and died young," says
Erickson. "They were like the James Dean of dinosaurs." The youngest
specimen - which had previously been labelled as a dwarf Tyrannosaurus - was
only two years old.

"We really have a new quantitative tool that will open up new avenues of
research, because now we can start asking questions about the biology of
extinct creatures like we can for living ones," says Peter Makovicky, one of
the team.

One such question is how did such dinosaurs move their gigantic bodies? Some
answers were presented at the International Congress of Vertebrate
Morphology, held in Florida, US, in August. For instance, John Hutchinson at
the Royal Veterinary College in Hatfield, UK described how interactive
software, which models a creature's mass, centre of mass and inertia based
on skeletal evidence, is revealing more about how T. rex walked.

Read the rest at NewScientist
http://www.newscientist.com/news/news.jsp?id=ns99996274

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