3 August 2019 | New Scientist | 45palaeontologist Catherine Forster of George
Washington University.
Finding every single species of dinosaur that
ever lived is an impossibility because the fossil
record is an incomplete transcript of life on
Earth. The best we have are small snapshots
from places where sediment was deposited,
such as floodplains and dune-covered deserts,
that were then thrust to the surface where
palaeontologists can find them. We will know
little, if anything, about those dinosaurs that
lived in environments that eroded away, like
mountains.
But there are ways to predict what may be
out there. One is to look at what has already
been found in a group to estimate what
undiscovered species might still be awaiting
discovery. This is where discoveries like the
tyrannosaur M. intrepidus – whose name is
derived from the Greek term for impending
doom – help. The earliest members of the
tyrannosaur family show up in North
America’s fossil record about 150 million years
ago. Yet they are then virtually absent until
about the 80-million-year mark, when they
re-emerge as giant, big-headed, tiny-armed
apex predators. “Tyrannosaurs just pop up in
North America during the last 15 million years
of the Cretaceous as large-bodied predators
sitting atop the food chain,” says Zanno.
M. intrepidus changes that story. Its bones
were first spotted jutting out of a site in Utah
back in 2013 ,and it was described as a new
species by Zanno and her colleagues earlier
this year. At 96 million years old, it sits right
in that gap and indicates that tyrannosaurs in
the region must have had their growth spurt
sometime between that 96 and 80-million-
year time slice. “Moros opens a window on
what the ecology of tyrannosaurs was like
before they rose to power,” she says.
M. intrepidus does something else, too.
There are now two fossil gaps on either side
of the dinosaur – its ancestors and its later
relatives – that are waiting to be filled. EachT
HE name “tyrannosaur” conjures up
images of towering predators with
enormous heads and ridiculously small
arms. But Moros intrepidus wasn’t like that.
This 96-million-year-old tyrannosaur was the
size of a deer, a lanky pipsqueak of a predator.
It is far from the only dinosaur to strut onto
the stage this year – 31 new species have been
named so far. There’s Bajadasaurus
pronuspinax, discovered in Patagonia, which
hit the headlines for the forward-facing spines
jutting from its neck, and little Ambopteryx
longibrachium, unearthed in China, which
confirmed that some feathery dinosaurs
flapped around using bat-like wings.
These add to a tally of more than a thousand
species of dinosaur known to have roamed
Earth in the Triassic, Jurassic and Cretaceous
periods – everything from tiny omnivores no
bigger than a pigeon to long-necked dinosaurs
that stretched over 30 metres long.
“The pace of dinosaur discovery is so fast
these days, one could label it frantic,” says
palaeontologist Lindsay Zanno of North
Carolina State University. And it shows no sign
of letting up just yet. It seems we are entering
the golden era of dinosaur discovery.
The very first dinosaurs evolved about 245
million years ago, during the early part of the
Triassic period (see diagram, page 46). Most
stayed small until a mass extinction of their
reptilian rivals cleared the way for dinosaur
domination during the Jurassic period. This
is when dinosaur evolution kicked into high
gear, and the trend continued through the
Cretaceous until another mass extinction
wiped out most dinosaurs 66 million years
ago. Birds are the only dinosaurs that survived,
which is why researchers often distinguish
between avian and non-avian dinosaurs.
Humans have long endeavoured to
understand dinosaurs. At Flag Point in
southern Utah, for example, pictographs
created nearly a thousand years ago by Native
Americans unmistakably document Jurassic
dinosaur tracks found nearby. Dinosaurs as we
know them today got their name in 1842, when
English anatomist Richard Owen first used
the word in a report on Britain’s fossil reptiles,
dinosaur meaning “terrible lizard”. At the
time, only three had been uncovered: the
carnivorous Megalosaurus, the herbivorous
Iguanodon and the armoured Hylaeosaurus.
The Great Bone Rush of the late 19th century
quickly increased that number, with classics
such as Triceratops and Ceratosaurus bringing
the ancient reptiles fame. Museums raced to
source showstopper specimens to draw in the
crowds. Yet while these might have impressed
the public, dinosaurs weren’t especially
inspiring to those who studied fossils and theevolution of life on Earth. For much of the 20th
century, many palaeontologists viewed these
creatures as anomalies that deserved their
extinction for being too big and strange to
survive. It took a renaissance in the late 20th
century – a total rethink of dinosaurs as hot-
blooded, successful animals – to spark the
ongoing search for ever more of them.
Explorations in Asia, South America and
elsewhere soon delivered a stunning array of
new species. Entire groups never seen before
were introduced, such as the bulldog-snouted,
carnivorous abelisaurs from the southern
hemisphere and the famous feathered-
dinosaurs from China. “When I compare what
we knew about dinosaurs when I was a student
and what we know now, I’m astounded,” says >“Dinosaurs were
viewed as
anomalies that
deserved their
extinction”