315-million-year-old fossil discovery in Canada suggests Tetrapod may be earliest plant-eater

A newly identified fossil from Cape Breton Island in Nova Scotia is reshaping scientists’ understanding of when vertebrates first began eating plants. The football-sized species, Tyrannoroter heberti, lived about 315 million years ago during the late Carboniferous Period and may represent the earliest known four-legged animal with teeth specialized for grinding high-fibre vegetation, according to a new study published in Nature Ecology and Evolution.

Tyrannoroter heberti lived about 315 million years ago in what is now Cape Breton Island, when most four-legged animals ate insects and other animals because they couldn’t yet digest plants.

According to the CBC website, a study in Nature Ecology and Evolution identifies the species as the earliest four-legged animal with plant-adapted teeth, a finding that “reshapes our understanding” of how quickly herbivory emerged, said lead author Arjan Mann.

All about Tyrannoroter heberti

Tyrannoroter belonged to a group known as microsaurs, small, lizard-like creatures that predated reptiles and mammals, yet were part of the broader lineage to which they belonged.

Much of its skull was found with other fossils embedded in the roots of a massive petrified tree stump along a seaside cliff on Cape Breton Island.

Paleontologist Brian Hebert discovered the three- to four-metre-wide stump about nine years ago, and the species name heberti honors him.

Fossils of similar species about 20 million years younger, including Pantylus, show short, squat bodies with large rib cages and digging adaptations, and experts believe Tyrannoroter likely looked much the same.

Most pantylids measured just five to 10 centimetres long, but researchers believe Tyrannoroter was about the size of a football, earning it the name meaning “tyrant digger.”

According to the CBC website, the most distinctive trait of Tyrannoroter is its multiple rows of “Hershey-kiss” shaped teeth, an advanced design for its era that enabled it to process shoots, leaves and other tough plant matter. Tetrapods first emerged on land approximately 375 million years ago, during the Devonian Period that came before the Carboniferous.

Although early tetrapods couldn’t digest plants, fossilized leaves show insect feeding, and evidence from teeth alone may not confirm herbivory. The earliest known plant-eating tetrapod was Desmatodon (303–306 million years ago); if Tyrannoroter was herbivorous, it would slightly predate that timeline.