An illustration shows what researchers believe Tyrannoroter heberti looked like.
Hannah Fredd
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A chunky, squat creature that roamed Earth 307 million years ago is helping scientists understand how plant-eating animals first appeared on land. The newly described species is one of the earliest known tetrapods — or four-limbed animals — to show evidence of having a plant-based diet.
The discovery, detailed in a study that was published Tuesday in the journal Nature Ecology & Evolution, centers on a skull found in a fossilized tree stump along the cliffs of Cape Breton Island in Nova Scotia. The species name, Tyrannoroter heberti, is a nod to the man who discovered the fossil, Brian Hebert, a local paleontology enthusiast.
“It translates to ‘Hebert’s tyrant digger,’” said co-lead study author Dr. Arjan Mann. The name combines the Greek words for “tyrant” and “plough man,” since its snout was likely used for digging.
The finding reveals that the oldest four-limbed land animals likely started eating vegetation around the middle of the Carboniferous Period, pushing back the timeline for the emergence of plant-eating vertebrates. “That’s pretty shortly after tetrapods transitioned fully to land,” Mann said.
Arjan Mann holds a 3D-printed replica of Tyrannoroter’s skull at Chicago’s Field Museum.
Field Museum
Using 3D scanning and printing, the team was able to study the fossil in remarkable detail. “It’s a way of digital preparation that allows us to visualize the skull and make 3D prints for our museum collections, for outreach, and to take around the world without risking the actual fossil,” explained Mann, curator of early tetrapods at Chicago’s Field Museum of Natural History.
After studying the fossil and comparing it with skeletons of relatives, the researchers were able to determine that Tyrannoroter heberti was “a little big, chunky, cute, football-sized, reptile-like thing,” similar to a shingleback skink, which is a type of lizard, Mann said. But what set this creature apart were its teeth and skull.
An Australian shingleback skink resembles what researchers believe the Tyrannoroter looked like.
G Lacz/imageBROKER/Shutterstock
The animal had a wide, heart-shaped skull and sizable teeth arranged in rows on the roof of its mouth and its lower jaw. These choppers fit together like puzzle pieces, allowing the animal to grind up tough, fibrous plants.
“This massive amount of surface area on its palate, covered in large, robust teeth, is probably a key adaptation to herbivory,” explained Mann, referring to plant feeding.
To confirm its plant-based diet, the research team relied on CT scans and electron microscopes to identify wear facets — areas where the teeth grind together. “Other animals with similar wear facets are herbivores during later time periods,” Mann noted.
The new research shows plant-eating evolved earlier and in more animal groups than previously thought, said Michael Coates, professor of organismal biology and anatomy at the University of Chicago who was not involved in the study. The findings shed light on how early land ecosystems developed, according to Coates.
