A fascinating new study suggests that our beloved Triceratops may not be exactly what we think:
DINOSAURS were shape-shifters. Their skulls underwent extreme changes throughout their lives, growing larger, sprouting horns then reabsorbing them, and changing shape so radically that different stages look to us like different species.
This discovery comes from a study of the iconic dinosaur triceratops and its close relative torosaurus. Their skulls are markedly different but are actually from the very same species, argue John Scannella and Jack Horner at the Museum of the Rockies in Bozeman, Montana.
Triceratops had three facial horns and a short, thick neck-frill with a saw-toothed edge. Torosaurus also had three horns, though at different angles, and a much longer, thinner, smooth-edged frill with two large holes in it. So it’s not surprising that Othniel Marsh, who discovered both in the late 1800s, considered them to be separate species.
Now Scannella and Horner say that triceratops is merely the juvenile form of torosaurus. As the animal aged, its horns changed shape and orientation and its frill became longer, thinner and less jagged. Finally it became fenestrated, producing the classic torosaurus form (see diagram, right).
This extreme shape-shifting was possible because the bone tissue in the frill and horns stayed immature, spongy and riddled with blood vessels, never fully hardening into solid bone as happens in most animals during early adulthood. The only modern animal known to do anything similar is the cassowary, descended from the dinosaurs, which develops a large spongy crest when its skull is about 80 per cent fully grown.
This sort of realization is so cool to me because it seems simple and intuitive, but it took us so long to figure out. We know that our contemporary organisms can make great morphological changes as they age – why didn’t we think the same thing about dinosaurs? And when you think of the magnitude of some of these changes, it makes you wonder what other dinos we have wrong. I mean, an alien looking down at our planet probably wouldn’t think a butterfly came from a caterpillar. But that’s an extreme example. Maybe an alien would label a baby and adult chicken differently.
What’s neater is that we can imply some things about the purpose of the frill just from knowing how it changes over time:
The finding has implications for the supposed defensive function of the triceratops’ frill. “If I was a triceratops I wouldn’t want anything too damaging to happen to my frill, as it had numerous large blood vessels running over the surface,” says Scannella. “I don’t imagine holding up a thin bony shield that can gush blood would be a very effective means of defence.”
Instead it is likely that the headgear was a display to signal an individual’s maturity to other members of the species. Differences between the sexes is another possibility but less likely, says Scannella.
But rest assured, Triceratops fans. Torosaurus is the species that is being abolished – our childhood memories are still in tact. Though I’m sure the Blue Ranger will be a little upset knowing he was riding a baby dinosaur this whole time.*
*Yes, I really am that geeky.