Scientists Discover Fossils of the Earliest Herbivore Mammal

Plants originally appeared on Earth around 470 million years ago, but there were no animals around to eat them.

Herbivores require specific characteristics such as strong teeth designed to break down tough plant material and a diverse gut microbiome to digest cellulose.

So scientists originally thought that plant-eating animals aka herbivores originated around 300 million years ago.

But the discovery of a new fossil could push back the evolution of herbivores even more by millions of years.

A recently published study by Smithsonian paleontologists, named a new species of ancient reptile-like mammal precursor with teeth like blue-tongued skinks, which eat everything from fruits and vegetables to insects^[1].

Where were The Fossils found?

These fossils were discovered in the town of Linton in Eastern Ohio, at the site of an abandoned coal mine. 

During the Late Carboniferous period, this area had a pleasant length of wetlands with coelacanths, spiny freshwater sharks, and a plethora of amphibians.

Colosseum, a giant frog with teeth and limited limbs that governed these ancient wetlands like a crocodile, was one of the strangest creatures.

According to researchers, these communities also housed the earliest reptiles and mammalian forerunners.

A wandering river changed course here about 307 million years ago, leaving behind an isolated riverbed known as an oxbow lake. 

Plant material from the surrounding swamp eventually accumulated in the sluggish water and degraded into the muck. 

The decomposition process drained oxygen from the surrounding water, dooming the inhabitants of the bog.

Scavengers were also kept at away by the lack of oxygen, ensuring that the fish, amphibians, and whatever else washed in were gently preserved in the peat.

Etymology and Anatomy of Creature

The creature was given the name Melanedaphodon hovaneci.

The name is a combination of the Greek word “melanos“, which means “black,” and the terms for “pavement” (edaphon) and “tooth” (odon), which relate to the animal’s dense clusters of teeth. 

The specific epithet hovaneci is named for George Hovanec, who generously helped with the funding to help with the CT scanning of Linton fossils.

The species was a near relative of Edaphosaurus, an early Permian reptile-like mammal progenitor known as a synapsid. 

Edaphosaurus, an alligator-sized, sail-backed herbivore, was one of Earth’s first major herbivores.

It possessed a large ribcage that housed a huge gut to digest its leafy food and robust teeth plates to chew down difficult vegetation.

The teeth of Melanedaphodon are distinct in that they culminate in bulbous tips.

They do, however, resemble the chompers of Edaphosaurus and numerous live lizards that devour plants.

They include giant skinks and tegus, a group of sturdy lizards native to South America that eat everything from fruits and eggs to rodents and restaurant scraps.

The researchers determined that Melanedaphodon is the oldest known amniote (the animal group that includes all reptiles, birds, and mammals) and can eat low-fiber plant leftovers like seeds and bark.

Melanedaphodon existed during a turbulent time in Earth’s history.

The huge coal jungles that dominated the Carboniferous period began to give way to drier habitats not long after the ancient residents of Linton, and Ohio, were buried beneath the bog, causing an extinction event.

True herbivores like Edaphosaurus had become prominent components of terrestrial ecosystems for the first time when the Permian epoch began around 299 million years ago.

References

1. Arjan Mann, Amy C. Henrici, Hans-Dieter Seus and Stephanie E. Pierce, ‘A new Carboniferous edaphosaurid and the origin of herbivory in mammal forerunners | Scientific Reports’, Scientific Reports, 5 April 2023, https://www.nature.com/articles/s41598-023-30626-8[↩]