The remains of trilobites, a diverse group of marine animals much
older than dinosaurs, are remarkably well preserved, providing fresh
insights of their anatomies and social behavior.
Trilobites may be the archetypal fossils, symbols of an archaic
world long swept beneath the ruthless road grader of time. But we
should all look so jaunty after half a billion years.
At the Smithsonian's National Museum of Natural History, Brian T.
Huber, chairman of paleobiology, points to a flawless specimen of
Walliserops, a five-inch trilobite that swam the Devonian seas
around what is now Morocco about 150 million years before the first
dinosaurs hatched. With its elongated, triple-tined head horn and a
bristle brush of spines encircling its lower body, the trilobite
could be a kitchen utensil for Salvador Dali. Nearby is the even
older Boedaspis ensifer, its festive nimbus of spiny streamers
pointing every which way like the ribbons of a Chinese dancer.
In a back room of the museum, Mr. Huber opens a drawer to reveal
a dark, mouse-sized and meticulously armored trilobite that has yet
to be identified and that strains up from its sedimentary bed as
though determined to break free.
"A lot of people, when they see these fossils, don't believe
they're real," said Mr. Huber, 54. He is fit from years of fieldwork
and proud that the state fossil of his native Ohio is a trilobite.
"They think they must be artists' models."
The fossils are real, and so, too, is scientists' unshakable
passion for trilobites, a diverse and illuminating group of marine
animals that once dominated their environment as much as dinosaurs
and humans would later dominate theirs -- and that still stash a few
surprises up their jointed sleeves.
In a series of reports, scientists have described fresh insights
into the trilobite's crystal-eyed visual system, unique in the
animal kingdom, and its distinctive body plan, a hashtag of
horizontal segments arrayed along three vertical lobes that allowed
the trilobite to roll up into a defensive ball against predators and
Other researchers have found evidence that some trilobites were
highly social, migrating long distances in a head-to-tail procession
as they searched for food, or gathering together during molting
season at a kind of Trilo's Retreat, where they could simultaneously
shuck off their carapaces and seek out mates.
"It looks like a lot of trilobite mating behavior happened when
they were in a soft-shelled form," said Carlton E. Brett, a
professor of geology at the University of Cincinnati, who has
presented research on trilobite assemblages to the Geological
Society of America and elsewhere. "They did it in the nude."
To investigate trilobite social life, Mr. Brett and his
colleagues analyzed numerous examples of mass burial sites, where
congregations of trilobites had been trapped in place by the
sedimentary upheavals from violent sea storms, just as the citizens
of Pompeii were smothered by Vesuvian ash. "You feel a little bad
for the trilobites, but it's incredible seeing these things
preserved in the act of life processes," Mr. Brett said. "It's
On a similarly erotic note, some researchers have proposed that
many of the more gothic features identified in the trilobite fossil
record -- the oversized head horns, the curlicue shoulder spines and
maybe the eyestalks that look like a couple of periscopes plunked on
either side of a trilobite's face -- are the trilobitic equivalent
of a peacock's tail, results of sexual rather than natural
By that argument, the showstoppers in a given collection are
probably males, their appurtenances having evolved to impress
females or intimidate rival males. "If you look at the diversity of
life now, most of the weird, exaggerated things we find are sexually
selected," said Robert J. Knell of the University of London.
"There's no reason to think evolution was working differently in the