from the October 21, 2009 edition -
http://www.csmonitor.com/2009/1021/p02s37-usgn.html
North America's tiniest dinosaur weighed less than a toy poodle
The tiny dinosaur, unearthed in Colorado and named Fruitadens haagarorum,
measures 29 inches from beak to tail and weighs less than two pounds.
By Peter N. Spotts | Staff writer of The Christian Science Monitor
>From a rock formation near Grand Junction, Colo., comes a tale of a dainty
dinosaur.
Meet Fruitadens haagarorum, though it might as well be called Fifi. It's
roughly the length of a toy poodle and a fraction of its weight.
It's the smallest dinosaur ever found in North America, according to an
international team of scientists formally describing the creature this week.
It stretches some 29 inches from beak to tail. In its day, it would have
weighed in at just under two pounds.
The fossil remains of six of these animals have been languishing in
storage at L.A.'s Museum of Natural History since they were unearthed between
1979 and the early 1980s. The creatures represent the latest examples of a
broader group of prehistoric animals that are proving to be far more diverse
than many people realized.
Fruitadens is the smallest known member of a group of dinosaurs known as
ornithischia – bird-hipped dinosaurs that include behemoths such as
Stegosaurus or Triceratops. For the most part, this group has been tagged as
"plants eaters."
>From what scientists can tell from the 150 million-year-old fossil's
teeth, however, Fruitadens wasn't picky. It ate whatever it could find –
veggies
or meat.
For a long time, people divided dinosaurs into the meat-eaters and
plant-eaters, observes Luis Chiappe, who heads the Dinosaur Institute at the
Natural History Museum in Los Angeles and is a member of the team reporting
the
find. "Now we're finding that the division is not so clear cut."
Fruitadens, he says, is a good example of a "plant eater" that ate bugs or
small reptiles, as well as plants. This ability to thrive on a range of
foods may account for its longevity. The dinosaur's 100-million-year-long
presence in the fossil record means "it's a very long-lived group," says Dr.
Chiappe.
The incredible shrinking dino
Fruitadens' size is intriguing, because it bucks a general trend toward
ever-larger bodies as dinosaurs evolved, explains Thomas Holtz Jr., a
paleontologist at the University of Maryland in College Park.
When dinosaurs split into two major groups – the bird-hipped and the
lizard-hipped – from a common ancestor, they were only about three to five
feet
long. Some bird-hipped ornithischia grew to sizable proportions – more than
50 feet long. But one subgroup, Heterodontosaurs, the family that
Fruitadens belongs to, remained smaller than most. Fruitadens started out
small and
shrank with evolutionary time.
The pattern of starting at a length of 3 to 5 feet and getting bigger is a
common trend among dinosaurs, says Dr. Holtz. But getting smaller from
that starting point "seems to be pretty rare."
Why did Fruitadens take the path to puny?
Evolutionary pressures from predators could have prompted the creature to
adopt the rabbit's approach: stay small, stay fleet, and hide – something
that would have been tougher for Fruitadens' distant cousins, duck-billed
plant-munchers that could grow up to 40 feet long.
Tree climbers?
Holtz offers up another intriguing possibility: Fruitadens may have been
able to climb trees to avoid being eaten. He notes that as therapods –
members of the lizard-hip gang – evolved into modern birds, the need to hunker
down in trees, or glide from one to another on early forms of wings, favored
smaller sizes.
As for Fruitadens, "there's nothing to keep these guys out of trees. After
all, even goats can climb trees," he says. "These guys are built better
for tree climbing than any goat ever was. So these could have been
tree-dwelling, bird-hipped dinosaurs."
While even smaller dinosaurs have cropped up among the lizard-hipped
group, Fruitadens may be reaching the lower limits for ornithischia.
It takes a sizable gut to digest plant material, explains Donald
Henderson, curator of dinosaurs at the Royal Tyrrell Museum in Drumheller,
Alberta,
and a member of the research team reporting its results in the current
issue of the Proceedings of the Royal Society B. And it's not clear one can
get
much smaller than Fruitadens and still keep roughage in the diet.
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