Almost every child goes through a dinosaur phase. In some
cases, it’s a frenzied week of roaring and leaving spiky plastic models all
over the floor, before a combination of sore feet and a sore throat drive you
onto the next stage of development. In my case, it lasted about 5 years. I
owned sacks of dinosaur toys, a library’s worth of dinosaur books, and
irritated my friends by criticising the accuracy of their dinosaur games (You
can’t play with a dinosaur from the Creataceous and a dinosaur from the
Jurassic at the same time. You just cannot.) Eventually, peer pressure made me
decide that dinosaurs were for little kids, and I forgot about them for a
decade or so.
But last year, I took a module in Palaeobiology-- the study
of extinct organisms-- as part of my degree. I was back in the realm of
dinosaurs-- older, wiser but still embarrassingly excited. Then as I delved
deeper into my external reading, I found some papers that shook my world,
shattered my dreams, and generally slapped my childhood in the face. My
dinosaur books had been lying to me about my favourite dinosaur of all time:
Deinonychus.
Deinonychus (pronounced Die-NON-ik-uss)
was a mean guy. Resembling its smaller, superstar cousin the Velociraptor,
Deinonychus nonetheless has its own claims to fame.
 |
| This particular specimen is a bit of a deviant, judging by his facial expression and his public nudity (we now know that Deinonychus probably had feathers) |
 |
| However, this guy has a far more modern dress-sense |
Before the 1960s,
scientists took a pretty dim view of dinosaurs. The consensus was that they
were all stupid, sluggish and cold-blooded, and probably died out because they
couldn’t cope with the same challenges that we sleek, sexy mammals can. But
that view started to fall apart when John Ostrom took a closer look at
Deinonychus. He suggested that these animals were speedy, intelligent
pack-hunters who worked together to bring down large prey, using the fearsome
sickle-shaped claw on each foot to disembowel their victims. Like wolves.
Slashy Captain Hook wolves. This image of Deinonychus helped create a
revolution in the way that we think about dinosaurs, and it was still
championed in all my dinosaur books. As the sort of child who didn’t bat an
eyelid at the bloodiest scenes of Watership Down, it inspired me. Over several
years, I built up a portfolio of really creepy drawings of dinosaurs killing each
other, made with nothing but a pencil and a red felt-tip pen, and ravaging
packs of Deinonychus featured heavily in my “art”. On reflection, I feel lucky
that my parents didn’t refer me to a child psychologist.
But in 2006, long after I’d abandoned dinosaurs in favour of
blushing at teenage boys, some scientists decided to test out the theories
about those fearsome feet. Phillip Manning and his team built an accurate hydraulic
model of a Deinonychus leg, complete with terror-claw, and made it kick a pig
carcass that had kindly volunteered to play the part of an herbivorous
dinosaur. Yet far from tearing the carcass into ribbons of sandwich ham, the claws
were AWFUL at doing any sort of tearing damage. Instead, they created small
shallow puncture wounds that did very little to the surrounding tissue, let
alone the internal organs. Not so much a river of blood and gore, then: if
Deinonychus behaved like my books said, then the herbivores probably walked
away with mildly painful wounds that cleared up in a week. Something else was
going on with these bizarre claws. Stumped, Manning suggested that Deinonychus
could have used its claws like crampons, allowing it to climb onto the backs of
large prey and attack from there. So my vision of dramatic battles between
massive herbivores and a fearsome pack of predators wasn’t totally shattered…
yet.
It was thanks to a guy called Denver Fowler that my artwork
really faded into fantasy. He noticed that modern eagles and hawks—known as
raptors—also have one claw bigger than the other on their feet. However, you’ll
never see a pack of eagles descending onto a cow in a field and slashing it to
death, neither do they need climbing aids. These birds hunt by swooping onto
smaller animals, then pick them to bits with their beaks, often while the prey
is still alive. A struggling animal could be very dangerous to a bird of prey,
potentially breaking its fragile bones, so it’s vital for the raptor to keep it
pinned down firmly. This is where that claw comes in. By clamping down with
their powerful modified talon, raptors immobilise their prey, allowing them to
concentrate on their (very fresh) meal without distraction. Fowler compared the
feet of raptors with those of their ancient cousin, Deinonychus, and found many
similarities in their anatomy. The flexibility of the toe bearing that large
claw may have come in handy not for delivering slashes… but for swivelling down
into a death grip on small prey. That’s right—small prey. Those epic clashes I’d
envisioned between huge herbivores and fierce little predators seemed less and
less feasible.
So how did Deinonychus ACTUALLY live? Fowler envisions a
solitary predator that pursued animals smaller or similar to its own size at
high speed. It would then pounce on top of its victim and press it firmly to
the ground, channelling its bodyweight through the tip of the powerful sickle-claws
to prevent escape. Then it would have
leaned forward and proceeded to rip its squirming dinner into bitesize
chunks—gory, but not quite the image I’d held. Fowler hadn’t gone as far as to
demonstrate that my favourite dinosaur was a peaceful vegetarian, but I have to
admit—he’d stolen just a little bit of its badassery. This doesn’t mean
Deinonychus stops being cool, though. In fact, it could teach us a lot about
the early days of its modern relatives: the birds.
Fowler compared modern raptors with Deinonychus once more,
and noticed how, when perching on struggling prey, raptors often beat their
wings vigorously. This keeps the bird in a prime position on top of the prey,
making sure its victim stays pressed to the ground. We’ve known for a while
that many predatory dinosaurs like Deinonychus had feathers on their skin--
perhaps the first chink to appear in their armour of terror. But scientists
have long argued about how the particular lineage of feathery dinosaurs that
evolved into birds first developed the “flight stroke”—the special high-powered
downbeat of the wings that creates lift. Looking at Deinonychus inspired Fowler
to come up with a new theory. If dinosaurs also stability-flapped their
feathered arms when making a kill, over the generations, it could have selected for greater upper body strength and the ability to beat the arms hard and
fast-- features that would later come in very useful when their descendants
took to the air. Although Deinonychus was not a direct ancestor of birds—it
appeared long after the first flying dinosaurs—it was closely related to them, so
it’s likely that they shared similar behaviour. So by looking at how
Deinonychus might have hunted, we can take steps in unravelling one of the
biggest, most controversial mysteries in all of Palaeobiology.
In future, then, perhaps we’ll look back on Deinonychus as triggering
a second revolution in how we see the dinosaurs. If I told that to my
7-year-old self, I hope she’d have been consoled. Deinonychus… you might not be
the psycho-killer of my imagination, but you’re still cool to me.
Naked creepy Deinonychus: By Mistvan (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Fluffy Deinonychus: By Peng 6 July 2005 16:32 (UTC) (selbst gemacht --Peng 6 July 2005 16:32 (UTC)) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
No comments:
Post a Comment