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Tyrannosaurus growth rate articles
From: Ben Creisler email@example.com
I don't have the full reference and abstract yet from the
new Nature, but in case these news items have not been
Teen T-rex had monster growth spurt
18:00 11 August 04 NewScientist.com news service
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
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.
Hutchinson has previously shown that T. rex?s size would
limit it to running at no more than 25 miles per hour. To
run any faster, the dinosaur?s skeleton would have to
support a biologically impossible amount of muscle (New
Scientist print edition, March 2002).
However, the weight limit on running fast only kicks in
for animals over about one tonne, which corresponds to a
juvenile T. rex around 12 years old.
His new models, which have been validated using ostrich
skeletons, which move in a similar way to T. rex, show
that the dinosaur?s posture was rather unsteady, hampered
by a strong tendency for the head to pitch forward.
However, inertia was a strong stabilising force for large
dinosaurs like T. rex.
Journal reference: Nature (vol 430, p 772)
Newswise ? Most teenagers have growing pains, but none
probably compared to those of Tyrannosaurus rex as it
ascended to adulthood more than 65 million years ago,
according to a Florida State University researcher.
>From around age 14 to 18, T. rex took on about 70 percent
of its adult mass, growing from a 1-ton carnivorous lizard
to a bone-crushing, 6-ton dinosaur eating machine with few
rivals in the prehistoric kingdom, according to FSU
biologist Gregory Erickson. At the peak of this spurt, T.
rex grew more than 4.5 pounds a day.
Erickson and his team of paleontologists are the first to
establish an accurate picture of how T. rex accelerated
its growth over a relatively few years to become
gargantuan while earlier, smaller relatives had much
slower growth. The scientists did this by counting growth
rings in the bones of T. rex and other members of its
family and calculating the corresponding body size by
measuring the circumference of the femur.
The research is featured as the cover story for the Aug.
12 edition of the journal Nature.
T. rex's growth rate is comparable to that of the modern
day elephant. But while elephants have a lifespan of more
than 70 years, T. rex lived no more than 30 years.
"We now know that T. rex lived fast and died young," said
Erickson and Peter Makovicky, dinosaur curator at The
Field Museum and a coauthor of the study, will join with
other team members at the Chicago museum on Wednesday to
announce their findings. The museum is home to Sue® [The
Field Museum], the world's largest, oldest and most
complete T. rex fossil, which was discovered in South
Dakota in 1990.
Erickson has spent much of his career exploring how some
dinosaurs got so big. The first dinosaurs to roam the
Earth some 225 million years ago were about a yard long
and weighed between 50 to 100 pounds, he said. The giants,
such a T. rex and A. sarcophagus, came along about 150
million years later.
"Almost every child asks: 'How did dinosaurs get so big?'
That has remained one of the great mysteries in
paleontology," Erickson said. "Here we cracked the code
for one family of dinosaurs, the Tyrannosauridae."
Like trees, dinosaur bones are marked by growth rings,
with a new one developing every year. But there was one
giant obstacle to counting the rings: Most of the big,
meat-eating dinosaurs' bones remodeled themselves as they
grew and become hollow, erasing much of the growth record.
A possible solution to this dilemma came to Erickson about
four years ago while examining Sue. He noticed that Sue's
rib bones were solid. Further investigation revealed that
the fibula (a leg bone) and some hipbones were also solid
and retained the full compliment of growth rings.
Erickson assembled a team of researchers from the American
Museum of Natural History, The Field Museum, Canada's
Royal Tyrrell Museum of Palaeontology, Stanford University
and the University of Iowa. They examined cross sections
of bones from 20 Tyrannosaurs that ranged from 2 to 28
years of age and establish T. rex's accelerated growth
rate during its teenage years.
The researchers verified their results by comparing the
dinosaurs' growth rings to those of modern-day alligators
and lizards, whose rings are similar.
Ten years ago such research may have been impossible,
Erickson said. Museums wouldn't have allowed scientists to
cut away at T. rex bones to examine growth rings because
there were only a few good specimens. But a flurry of
discoveries in the past decade - there are now more than
30 known T. rex specimens worldwide - have given museums a
greater comfort level and allowed more invasive scientific