Pint-sized Mongolian menace shows dinosaurs loved the nightlife, too
"Shuvuuia might have run across the desert floor under cover of night, using its incredible hearing and night vision to track small prey such as nocturnal mammals, lizards and insects."
The fossilized skeleton of the small bird-like dinosaur Shuvuuia deserti is seen in this undated handout image. (photo credit: MICK ELLISON/AMNH/HANDOUT VIA REUTERS
Under the cover of darkness in desert habitats about 70 million years ago, in what is today Mongolia and northern China, a gangly looking dinosaur employed excellent night vision and superb hearing to thrive as a menacing pint-sized nocturnal predator.
Scientists
said on Thursday an examination of a ring of bones surrounding the
pupil and a bony tube inside the skull that houses the hearing organ
showed that this dinosaur, called Shuvuuia deserti, boasted visual and
auditory capabilities akin to a barn owl, indicating it could it hunt in
total darkness.
Their study, published in the journal Science, showed that
predatory dinosaurs overall generally possessed better-than-average
hearing - helpful for hunters - but had vision optimized for daytime. In
contrast, Shuvuuia (pronounced shu-VOO-ee-ah) loved the nightlife.
Shuvuuia
was a pheasant-sized, two-legged Cretaceous Period dinosaur weighing
about as much as a small house cat. Lacking the strong jaws and sharp
teeth of many carnivorous dinosaurs, it had a remarkably bird-like and
lightly built skull and many tiny teeth like grains of rice.
Its
mid-length neck and small head, coupled with very long legs, made it
resemble an awkward chicken. Unlike birds, it had short but powerful
arms ending in a single large claw, good for digging.
"Shuvuuia
might have run across the desert floor under cover of night, using its
incredible hearing and night vision to track small prey such as
nocturnal mammals, lizards and insects. With its long legs it could have
rapidly run down such prey, and used its digging forelimbs to pry prey
loose from any cover such as a burrow," said paleontologist Jonah
Choiniere of the University of the Witwatersrand in South Africa, the
study's lead author.
"It's
such a strange animal that paleontologists have long wondered what it
was actually doing," added paleontologist Roger Benson of the University
of Oxford in England, who helped lead the study.
The researchers looked at a structure called the lagena, a curving
and finger-like sac that sits in a cavity in the bones surrounding the
brain and is connected to the part of the ear that lets reptiles and
birds keep balance and move their heads while walking. Acute hearing
helps nocturnal predators locate prey. The longer the lagena, the better
hearing an animal has.
Some Dinosaurs Loved the Nightlife, Apr 14, 2011
A narrated slideshow of images related to an article by Lars Schmitz and
Ryosuke Motani at the University of California, Davis titled,
"Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit
Morphology." The article appeared in the 14 April 2011 issue of Science
Express, published by AAAS
The
barn owl, a proficient nocturnal predator even in pitch-black
conditions, has the proportionally longest lagena of any living bird.
Shuvuuia is unique among predatory dinosaurs with a hyper-elongated
lagena, almost identical in relative size to a barn owl's.
The
researchers also looked at a series of tiny bones called the scleral
ring that encircle the pupil of the eye. It exists in birds and lizards
and was present in the ancestors of today's mammals. Shuvuuia had a very
wide scleral ring, indicating an extra-large pupil size that made its
eye a specialized light-capture device.
The
study found that nocturnality was uncommon among dinosaurs, aside from a
group called alvarezsaurs to which Shuvuuia belonged. Alvarezsaurs had
nocturnal vision very early in their lineage, but super-hearing took
more time to evolve.
"Like
many paleontologists, I once considered that nighttime in the age of
dinosaurs was when the mammals came out of hiding to avoid predation and
competition. The importance of these findings is that it forces us to
imagine dinosaurs like Shuvuuia evolving to take advantage of these
nocturnal communities," Choiniere said.
Benson
added, "This really shows that dinosaurs had a wide range of skills and
adaptations that are only just coming to light now. We find evidence
that there was a thriving 'nightlife' during the time of dinosaurs."
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