Two hundred million years ago, the world's most fearsome fangs came bundled in an appropriately bite-sized package. Measuring just two inches long, eel-like creatures known as conodonts may not have looked like much from a distance — but up close, their mouths were the stuff of nightmares.
Conodonts are widely regarded as some of the most successful vertebrates that ever lived, evolving some 500 million years ago and thriving for close to 300 million years before being wiped from existence by the Triassic-Jurassic extinction event.
Their teeth, while small, were undeniably unique. For one thing, the were incredibly sharp; the fossilized teeth pictured up top belonged to a conodont species named Wurmiella excavata, and are the sharpest teeth ever discovered. The tips measure just 2 micrometers across. (The word "conodont" is derived from the Greek konos, for "cone," and odous/odont, for "tooth.")
But sharp is not always a good thing. As paleobiologist Philip Donoghue and his research team explain in the latest issue of Proceedings of The Royal Society B, "high sharpness renders the elements demonstrably vulnerable to wear and breakage." How, then, did conodonts like W. excavata go about eating, without smashing their razor sharp chompers to bits?
To find out, Donoghue and his team created computer models of W. excavata's teeth to understand how they might have functioned without being crushed like chalk. And it turns out these "chompers" didn't do much chomping, at all.
Nature News gives us a tidy summary of the team's findings:
The team found that the conodonts did not process food using a mechanism based on muscular force, as mammals do. Instead, they relied on minuscule forces that became extremely concentrated as a result of their teeth's extreme sharpness, and the special way in which they gnawed.
Unlike mammalian teeth, which close perpendicularly (up and down), conodont teeth turned that action 90 degrees, slicing food from left to right. "The inter-angles of the blade-like teeth would have been trapped first at the back, rocked forward and separated again," explains Donoghue.
The team's findings hint at how such sharp (albeit delicate) teeth could have evolved in the first place. Without the jaw muscles to make an action like chewing possible, conodonts had to evolve structures sharp enough to translate even the tiniest of motions into powerful, food-shredding force. In doing so, however, W. excavata evolved teeth that would be completely impractical in the mouth of a bigger creature, or one with more muscular jaws.
How, then, did future vertebrates come to develop the teeth that we're all familiar with today? Did different dental structures emerge independently as the need for pre-digestive food-processing became necessary for survival (a common hypothesis), or did they somehow manage to evolve from the razor-sharp serrations of creatures like conodonts? It's exciting to imagine how modeling techniques like the ones used by Donoghue's team will improve our understanding of vertebrate dental evolution in the years to come.