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WITH a crack of his bullwhip and a touch of computer wizardry, Nathan
Myhrvold conjures up a prehistoric sonic boom. It is an echo from more than 100
million years ago when plant-eating giants called apatosaurs were alive and
generating 200 decibels with each swipe of their tails. A tonne and a half of
flesh and bone moving from side to side must have created quite a spectacle, but
what use was it? Myhrvold particularly likes the idea that it might have been
some form of mating display. Of course, there鈥檚 no knowing for sure. 鈥淏ehaviours
don鈥檛 fossilise all that well,鈥� he admits.

This lack of evidence has put the study of dinosaur behaviour beyond the pale
for some palaeontologists. But Myhrvold, who holds down a day job as chief
technology officer at Microsoft in Redmond, Washington, relishes a challenge. In
fact, his ambitious goal of recreating the lives of long-dead animals is shared
by a growing number of researchers. Ingenuity, lateral thinking and a forensic
scientist鈥檚 eye for detail are the tools of their trade as they search for clues
among the scant remains of another age.

Take Tyrannosaurus rex, 鈥渒ing of the tyrant lizards鈥�. Dinosaur
detectives who want to get under this monster鈥檚 skin have meagre evidence to
work with. The first specimen was found in 1900, and since then excavations have
turned up only three animals that are more than half complete. The same sites in
America鈥檚 Midwest have yielded another 20 or so skeletons that are at least 15
per cent intact. Even so, clever dino-sleuths have turned up plenty of clues
upon which to work their magic. Jurassic Park it isn鈥檛, but this work
paints a pretty good picture of what a day in the life of a T. rex
might have been like.

Rise and shine

Were tyrannosaurs and their ilk cold-blooded, relying on outside heat to warm
their bodies and get them going? Or could they remain active whatever the
temperature of their surroundings, by burning metabolic fuel to generate their
own body heat? The long-running controversy over whether dinosaurs were
ectothermic, like modern lizards, or endothermic, like birds and mammals, is
central to our understanding of their lifestyles.

In one strand of research, John Ruben and his colleagues at Oregon State
University in Corvallis have been using CAT scanning to probe the secret
recesses of dinosaurs鈥� noses. The team found that an assortment of
dinosaurs鈥攊ncluding a member of the tyrannosaur family鈥攈ad
relatively narrow nasal passages which would have had little space for special
scroll-shaped structures called respiratory turbinates. Existing endotherms use
these as air conditioners to moisten and warm incoming air and recover some heat
and moisture from outgoing air鈥攅ssential processes when breathing rates
are high, as they are in endotherms. The implication is that the dinosaurs had
low breathing rates and so wouldn鈥檛 have inhaled enough oxygen to fuel the high
metabolic rate needed for life as an endotherm.

In another study, the Oregon team focused on the lung structure of the famous
Chinese 鈥渇eathered dinosaur鈥�, Sinosauropteryx (This Week, 19 April 1997,
p 6). A distant relative of tyrannosaurs and a fellow member of the Theropoda
group, this fossil comes from the Yixian formation in northeast China, where a
treasure trove of exquisitely preserved prehistoric remains is being unearthed.
Astonishingly, signs of soft tissues are visible in the fossil, and these have
helped the team to conclude that Sinosauropteryx had relatively
simple, crocodile-like lungs that would be incapable of achieving the rates
of gas exchange most endotherms need.

What does this all mean for dinosaurs? According to Ruben they didn鈥檛
necessarily have the same rate of oxygen consumption or activity as living
lizards. 鈥淭hey could have had something intermediate,鈥� he says. 鈥淏ut the
evidence from this seems to preclude the possibility that they would have been
warm-blooded in the sense that we鈥檇 ordinarily think of warm-blooded
补苍颈尘补濒蝉.鈥�

Ruben points out that this doesn鈥檛 necessarily mean that dinosaurs were
sluggish and dozy. After all, they lived at a time when the world was warm, and
their large bulk would have helped them to keep a steady body temperature.
Today鈥檚 Komodo dragon offers a clue to what they might have been like. 鈥淚f we
were to reconstruct theropod dinosaurs with the same sort of metabolic
physiology we see in some of these very active lizards we would come up with a
very active, dangerous animal that would have been very mammal-like in its
behaviour,鈥� says Ruben.

First brush your teeth

One palaeontologist memorably described the huge, curved teeth of T.
rex as 鈥渓ethal bananas鈥�. Their serrated edges and the slots between the
serrations were extremely good at trapping meat fibres, according to
Chicago-based researcher William Abler. As a result, T. rex almost
certainly had terrible breath and its mouth would have been a dental hygienist鈥檚
nightmare. Abler believes its bite may have caused serious infections in any
prey that survived an attack.

Even so, until recently some experts believed that this impressive oral
weaponry was rather fragile. Then, a few years ago, Gregory Erickson was
studying for his master鈥檚 degree at the Museum of the Rockies in Montana when
Ken Olson, a fossil collector, appeared with a Triceratops pelvis. The
pelvis bore some extraordinary bite marks that looked like the work of T.
rex. 鈥淚f you took your thumb and pushed it down into clay鈥攖hat was
the depth of the holes,鈥� says Erickson.

Erickson and Olson鈥檚 studies on the pelvis suggested that T. rex fed
by 鈥減uncture-and-pull鈥� biting. 鈥淭hey鈥檇 bite very deeply into flesh and bone and
once they stopped they鈥檇 pull straight back,鈥� says Erickson, 鈥渁nd that would rip
out a big chunk of flesh.鈥� With a group of colleagues at Stanford University,
Erickson staged further tests to try to measure the bite force of a T.
rex. The team simulated bites on a cow鈥檚 pelvis using a life-size replica
tooth and a hydraulic press, and measured the force needed to produce holes like
the ones on the Triceratops specimen. The results showed that T.
rex would have chomped like a champion, producing a force of at least 13.4
kilonewtons鈥攐utperforming wolves and lions, and biting in the same league
as alligators.

Off to work

In Hollywood, T. Rex runs races with Jeeps, but some researchers
doubt it was so fleet. McNeill Alexander of Leeds University has looked for
clues about the running speeds of various dinosaurs by studying the structure of
their leg bones. He calculates a 鈥渟trength indicator鈥� which represents the
strength of the bones in relation to the animal鈥檚 weight. 鈥淚f you do that for
Tyrannosaurus you find that the leg bones were relatively weak for an
animal that was that heavy,鈥� he says. Faster animals need stronger leg bones and
his approach suggests that T. rex, which could have weighed 6 tonnes or
more, moved more like an elephant than a rhino or a gazelle. 鈥淲e鈥檙e not talking
about the sort of speeds that are good if you鈥檙e going to chase jeeps,鈥� says
Alexander. He offers a tentative figure of about 25 kilometres an hour. That鈥檚
less than half the speed of one modern top predator, the lion.

However, Theagarten Lingham-Soliar of the Russian Academy of Sciences in
Moscow argues that tyrannosaurs might have been faster than their bone structure
alone implies, because of other factors such as the presence of large,
shock-absorbing chunks of cartilage in their legs and their highly flexed
knees.

With a little lateral thinking, James Farlow and his colleagues at
Indiana-Purdue University at Fort Wayne have come up with another ingenious way
to deduce tyrannosaurs鈥� top speed. They asked themselves: what damage might a
fully grown T. rex do to itself if it came a cropper at speed? A fall
at 72 kilometres an hour, they calculated, could have been fatal. They came up
with a top speed of about 36 kilometres an hour. 鈥淔or an animal its size, I
think it was pretty fast,鈥� says Farlow. 鈥淚 suspect it could have caught any
other large dinosaur in its environment.鈥�

In theory, fossil footprints could provide decisive evidence, but there are
very few known tyrannosaur tracks, says Martin Lockley of the University of
Colorado, Denver. The best, in New Mexico, shows just one footprint with
about 3 metres of untrampled surface in front of it. It鈥檚 difficult to draw
conclusions from a single footprint, says Lockley, but if this distance is taken
as the distance between steps, then the calculations show that the animal was
travelling at around 11 or 12 kilometres an hour. Of course, this need not
represent its top speed. It may well have put on a spurt when in pursuit of its
dinner.

Dinner time

The idea that T. rex was a mighty hunter looks like an open-and-shut
case. But is it? According to some researchers, including palaeontologist Jack
Horner of Montana鈥檚 Museum of the Rockies, there is evidence that this
terrifying beast lived by scavenging. Horner points out that T. rex鈥檚
femur was longer than its tibia, whereas bipedal animals that run fast have the
opposite arrangement. T. rex appears to be adapted for long-distance
walking, he says. Its brain had a huge olfactory lobe鈥攍ike that of a
turkey vulture, which depends on smelling carrion from a long way off. And those
extraordinarily small arms look hopeless for grappling with prey. What鈥檚 more,
its physique would have been ideal for scaring hunters away from a fresh
carcass.

Most researchers still see T. rex as the most ferocious predator of
its day, although it might have scavenged when it got the chance, just as modern
hunters do. 鈥淚 would be astonished if tyrannosaurs had not been hunters as well
as scavengers,鈥� says Farlow. Hunting was their main method of procuring food,
according to Lingham-Soliar. He bases his conclusion on studies of tyrannosaur
anatomy and comparisons with modern animals. In particular, he points to the
huge skulls of tyrannosaurs, which were immensely strong in critical areas and
clearly designed to resist large stresses such as those that might be
encountered in hunting and dismembering large prey.

The same imposing anatomy has prompted David Norman of the University of
Cambridge to suggest that T. rex might have charged at its victims with
mouth agape. Lingham-Soliar, on the other hand, believes that this would have
been highly damaging to their teeth: 鈥淟ike running at a brick wall with one鈥檚
mouth open.鈥� He offers a different rationale for the stoutly built skull, which
also explains how tyrannosaurs managed to break up their prey despite their lack
of effective grasping forelimbs. He believes they tore their victims apart by
seizing them in the mouth and shaking them violently鈥攔ather like many of
today鈥檚 marine predators that also feed without the help of limbs, such as
sharks and killer whales. Enormous forces would have acted upon the skull and
neck, putting a premium on size and strength. Larger prey wouldn鈥檛 have been
shaken, but chunks of flesh would have been gouged out with the teeth, he
says.

Family life

Female tyrannosaurs were larger than males. That鈥檚 the conclusion of Peter
Larson from the Black Hills Institute of Geological Research in South Dakota,
following his discovery of two distinct body types in T. rex. 鈥淭he
pelvis in the robust form is wider inside, which might be an indication that
this form is female,鈥� says Larson. Further evidence comes from a living
descendent of dinosaurs. Male crocodiles have an extra bone known as a chevron
at the base of their tail where the muscle that retracts the penis is attached.
The same is true of saurornithoides, a group of dinosaurs from China that are
closely related to tyrannosaurs. Larson is looking for a similar pattern. 鈥淚
haven鈥檛 got absolute proof on T. rex yet,鈥� he admits. The clincher will
come later this year when the robust skeleton of Sue, the most complete T.
rex ever found, goes on display at Denver Museum of Natural History. 鈥淚
believe we鈥檙e going to find that Sue has one less chevron than the males,鈥� says
Larson.

Finding that female tyrannosaurs were more stoutly built than males is not as
surprising as it sounds. Larson points out that, contrary to most people鈥檚
expectations, throughout the animal kingdom females tend to be larger than
males, because of the obvious advantages for laying eggs or carrying young. 鈥淭he
only time you see males larger is where they have a harem and have to compete
for females,鈥� he says. 鈥淭. rex was not a herding animal in that sense.鈥�
He goes even further, pointing out that in birds of prey鈥攚hich are
probably among dinosaurs鈥� closest living relatives鈥攐utsized females and
monogamy go hand in hand. 鈥淭yrannosaurs may have pair-bonded,鈥� concludes
Larson.

Another palaeontologist who wants to dispel the image of T. rex as a
loner is Tom Holtz from the University of Maryland, College Park. He points out
that Sue was found in what looks like a family group, with a male and two
juveniles. And this is not an isolated example. 鈥淭here are multiple occurrences
of multiple rexes,鈥� says Holtz. 鈥淲hether or not they hunted together or had
division of labour within the group is difficult to tell.鈥� Pact hunting in
T. rex society is Myhrvold鈥檚 current area of interest, but he is yet to
publish his results.

鈥淭. rex probably organised into highly social, protective and
cooperative family groups,鈥� concludes Larson. Even if this harmonious picture is
correct, other clues suggest that there were outbreaks of violence between
individuals. For example, tyrannosaur teeth sometimes bear telltale marks made
by the teeth of their fellows. These could have been made during feeding,
fighting or courtship, according to Abler. Then there are the numerous broken
bones found in fossilised specimens. Many of these were healed by the time of
the animal鈥檚 death, suggesting that struggles with prey and competitors were
common. Bite marks on Sue鈥檚 skull show that she died after the left side of her
face was almost torn off by another T. rex. Even before this brutal
attack Sue鈥檚 life must have been agony. Research last year at the Denver Museum
of Natural History revealed that Sue suffered from gout.

THE SKULL of a so-called trombone duckbill discovered in New Mexico in 1995
was as impressive as the beast鈥檚 name implies. In life, this hadrosaur, formally
known as Parasaurolophus, was a ten metre giant and its crowning glory
was an enormous, hollow crest on top of its head. Long, looped tubes led from
the nostrils up to the top of the crest and then back down towards the
throat.

Some people think the crest acted as a resonator, and in 1981 David
Weishampel of Johns Hopkins University in Baltimore, Maryland, worked out how it
might have sounded. But the New Mexico discovery presented researchers with an
opportunity to find out more about the musical properties of this bizarre
structure.

With the help of a hospital in Albuquerque, Tom Williamson of the New Mexico
Museum of Natural History and Science and Carl Diegert of Sandia National
Laboratories took a CAT scan of the skull, which is 1.5 metres long. The
internal arrangement of tubes and chambers in the specimen turned out to be very
different from what they had expected.

To work out how the crest may have sounded, Williamson and Diegert modelled
it on high performance computers. No one knows whether dinosaurs had vocal
organs, but either way Parasaurolophus would have put on an impressive
performance. Without vocal organs, it could have got sounds to resonate in the
crest just as you can produce noises by blowing across the top of a bottle. The
result would have been a very low note (similar in pitch to the lowest note on a
piano). With vocal organs, it would have been rather more musical, producing a
wider repertoire of frequencies. The sound has been compared to that of a
didgeridoo.

Williamson believes that the crest would have been used for both visual and
vocal displays, maybe to attract mates. The low-frequencies would have travelled
well through the dense vegetation in which Parasaurolophus lived. They
could have been used to coordinate the movements of a group or even as alarm
calls.

The sounds can be heard on the web at http://www.nmmnh-abq.mus.nm.us/
nmmnh/nmmnh.html