Cretaceous period, 65-144 million years ago. Adult
Triceratops could be nearly 10 feet tall and 26 feet long, with a bony frill around the head
that was as wide as seven feet across. Two three-foot horns typically curved forward from the brow,
while a third horn erupted from the nose above a narrow, horny beak.
The baby's skull, along with a few
vertebrae, teeth and bony tendons, were discovered by amateur fossil hunter Harley Garbani in 1997 in
Montana's Hell Creek Formation, the source of many Triceratops and T. rex fossils. Garbani
thought he'd found the skull of a dome-headed dinosaur, or pachycephalosaur, and sent Goodwin a photo
of the bones he had reconstructed from hundreds of fragments. But Goodwin immediately recognized the
bones that make up the frill around the back of the head as those of a very young Triceratops
and assembled them into a skull and lower jaw that is missing only the nose and beak.
The fossil has been a unique
addition to the world's existing, mostly adult specimens of Triceratops. And the "yearling,"
as Goodwin called it, fits
perfectly into a study he is conducting with Jack Horner of Montana State
University about the growth patterns of Triceratops and other dinosaurs.
Although Goodwin's conclusions about
the lifelong growth of Triceratops will be published later this year, the baby skull offers its
own insights. For one, the surface of the skull shows grooves where blood vessels used to be, evidently
to nourish a fingernail-hard covering of keratin that was similar to the thicker layer that covered the
adult skull. Such horny coverings are often brightly colored in the living descendents of dinosaurs
the birds suggesting that adult Triceratops and their young may have been colorful, too.
In addition, the scalloped edges of
the baby's frill became mere wavy edges in the adults, although the scallops foreshadowed the development
of triangular scales along the edge of the adult frill, probably an attribute of sexual maturity,
Goodwin said. The two brow horns started out straight and short in the baby they're about an
inch long but ended up long and curved forward in the adult, while the nose horn became larger,
like that of a rhinoceros, although it was made of bone in Triceratops.
The brain case of the baby also
changed significantly, he said. Hidden beneath the bony frills of the skull, the hazelnut-sized brain of
the baby fit