Ancient ‘Tyrannoroter’ Rewrites the History of Herbivory
A newly discovered ancient tetrapod, Tyrannoroter heberti, is challenging long-held beliefs about the origins of plant-eating among land animals. Dating back 307 million years, this creature possessed specialized teeth and jaws indicating a predominantly plant-based diet, pushing back the known timeline for the evolution of herbivory.
The discovery, detailed in the journal Systematic Palaeontology, reveals that experimentation with plant-eating began surprisingly early in the evolution of four-legged land vertebrates – the ancestors of all reptiles, mammals, and birds. For over 100 million years prior to the emergence of these early tetrapods around 370 million years ago, plants enjoyed a relatively peaceful existence on land, largely untouched by herbivorous creatures.
“This is one of the oldest known four-legged animals to eat its veggies,” explains a senior evolutionary biologist at the Field Museum in Chicago and co-lead author of the study. “It shows that experimentation with herbivory goes all the way back to the earliest terrestrial tetrapods – the ancient relatives of all land vertebrates, including us.”
A Fearsome Name, A Vegetarian Diet
Despite its intimidating name – translating roughly to “tyrant rooter” – Tyrannoroter heberti was a relatively small animal, measuring approximately 25 centimeters (10 inches) in length. Researchers believe it belonged to a group called pantylids, which represent a crucial stage in the adaptation of animals to life on dry land.
The fossilized skull of Tyrannoroter was unearthed within a fossilized tree stump in Nova Scotia, Canada. Utilizing high-resolution micro-CT scanning, paleontologists meticulously examined the skull’s internal structure, focusing on the teeth to unlock the secrets of its diet.
Dental Batteries: A Key to Plant Consumption
The scans revealed a remarkable adaptation: alongside typical teeth, Tyrannoroter possessed sets of bony plates known as dental batteries on the roof of its mouth and in its lower jaw. These plates, also found in later herbivores like dinosaurs, functioned like a grinding mill, breaking down tough plant matter.
“We were most excited to see what was hidden inside the mouth of this animal once it was scanned – a mouth jam-packed with a whole additional set of teeth for crushing and grinding food, like plants,” says a senior paleontologist at Carleton University in Canada and the study’s lead author.
Not Quite Vegan, But a Significant Step
While Tyrannoroter likely favored plants, researchers suggest it wasn’t a strict vegan. The creature probably supplemented its diet with insects or arthropods when available. In fact, the evolution of dental batteries may have initially served to crush the exoskeletons of these invertebrates.
The researchers theorize that this adaptation later proved beneficial for processing plant material. Furthermore, consuming insects that had themselves fed on plants could have introduced the necessary microbiome into the tetrapods’ guts to effectively digest cellulose.
Rewriting the Evolutionary Timeline
Intriguingly, subsequent re-examination of other pantylid specimens revealed similar herbivorous dental structures, including one dating back as far as 318 million years. These findings, combined with other recent studies, provide compelling evidence that herbivory arose rapidly following the initial colonization of land by tetrapods.
“These findings, among other recent studies, provide direct evidence that revise the timeline of the origin of herbivory, revealing that various herbivorous forms arose quickly following terrestrialization of tetrapods,” the researchers write.
The discovery of Tyrannoroter heberti offers a fascinating glimpse into the early evolution of plant-animal interactions and underscores the remarkable adaptability of life on Earth.
