Compared with mammals, living members of the crocodile clan have exceptionally boring dentition.
From the slender-snouted gharials of India and the nocturnal caimans of South America
to the saltwater behemoths of the South Pacific, crocodile teeth vary little in morphology.
All are conical and pointed. Each tooth in an animal's mouth is almost identical to its neighbours—
as befits a group of that feed on a mixture of fish and the occasional careless beast
that strays too close to the shore, or even into the water itself.
This predilection for pointed fangs is not, however, how it has always been.
During the days of the dinosaurs, the Jurassic and Cretaceous periods,
crocodile-clan members showed extraordinary dental diversity.
Many of their teeth have proved so bizarre that some palaeontologists have theorised that,
far from being carnivorous, these ancient species might have been eating plants.
A study published this week in Current Biology, by Keegan Melstrom and Randall Irmis at the University of Utah, confirms this.
本周犹他大学的Keegan Melstrom和Randall Irmis在《Current Biology》发表的一项研究证实了这一点。
It also suggests that herbivory evolved in the crocodile clan on several occasions.
When trying to work out what ancient animals ate, palaeontologists usually look to modern analogues.
If teeth from an extinct beast match those of a modern species, the two are quite likely to have had similar diets.
With extinct crocodilians, however, this palaeontological tactic has routinely been stymied
because their teeth, which are adorned with many rows of cusps and wrinkled enamel,
look nothing like what is found in the mouths of animals alive today.
This has left the topic of what ancient crocodilians ate very much up for grabs.
Some palaeontologists argue that certain species, such as Simosuchus clarki were vegetarian.
To solve the puzzle Mr Melstrom and Dr Irmis turned to Orientation Patch Count Rotated (OPCR) analysis.