Scientists Discover Earliest Ancestor of Land Herbivores

Posted on April 16, 2014

Scientists have discovered the earliest ancestor of land herbivores. A 300-million-year-old fossilized juvenile skeleton of Eocasea martini was discovered in Kansas. Eocasea is pictured in the footprint of largest known herbivore of its time, Cotylorhynchus, in the above artwork by Danielle Dufault. Eocasea lived nearly 80 million years before the age of dinosaurs. It was about 6.5 inches long and weighed about 2 kilograms (4.4 pounds) as an adult.

Eocasea was carnivorous and fed on insects and small animals. Much larger herbivores evolved from it. Herbivores could take advantage of the more plentiful food source of terrestrial plants.

Paleontologist Robert Reisz, a professor in the Department of Biology at the University of Toronto Mississauga, says in the announcement, "The evolution of herbivory was revolutionary to life on land because it meant terrestrial vertebrates could directly access the vast resources provided by terrestrial plants. These herbivores in turn became a major food resource for large land predators."

Reisz and colleague Jorg Frobisch of the Museum fur Naturkunde and Humboldt-University in Berlin, discovered that Eocasea martini belonged to the caseid branch of the group Synapsid. This group, which includes early terrestrial herbivores and large top predators, ultimately evolved into modern living mammals.

Frobisch says, "Eocasea is one of the oldest relatives of modern mammals and closes a gap of about 20 million years to the next youngest members of the caseid family. This shows that caseid synapsids were much more ancient than previously documented in the fossil record."

The research was published here in the journal PLoS One.

ANIMALS