Between 16 million and 7 million years ago, the prehistoric Epicyon haydeni – the largest dog species ever to live – once grew to the size of grizzly bears and pounced on their equally massive prey like foxes and coyotes of today.
And you thought 2019 was a scary time to be alive.
Those are just part of the findings from research published in Scientific Reports studying how ancient predators hunted. To do so, researchers analyzed the skulls of lions, wolves, and hyenas – a group of mammalian top predators collectively known as carnivorans – to understand how prehistoric dogs hunted some 40 million years ago. After comparing computerized scans of fossils against modern animals, researchers created digital models of inner ears of 36 carnivorans, including six extinct species, in order to show how prehistoric predators hunted.
While previous studies used dental and limb morphologies to better understand the evolutionary lineage of prehistoric hunting methods, researchers say the inner ear, the mechanosensory organ responsible for balance and hearing, tells us more about how these animals moved and oriented themselves in the world. The height, width, and length of three semicircular canals in the ear show the animal’s function while the diameter of canals and height of cochlea suggest phylogenetic signal.
"For me, the inner ear is the most interesting organ in the body, as it offers amazing insights into ancient animals and how they lived,” said lead researcher Julia Schwab in a statement. “The first dog and the largest-ever dog are such fascinating specimens to study, as nothing like them exists in the world today."
Three of the bony canals in the inner ear changed over millions of years as animals adopted different hunting strategies. The world’s fastest predators, such as cheetahs, lions, and wolves, developed large ear canals in order to keep their head and vision stable while chasing or ambushing prey at high speed. Morphological differences in the ear canal also tell researchers how an animal killed its prey and whether they pursued, pounced, ambushed, or just periodically hunted, as well as provided insight into their phylogenetic relationships and whether they were related to today’s dogs (Canoidea) or cats (Feloidea).
“The results demonstrate that the bony labyrinth provides a powerful ecological proxy reflecting both predatory habits as well as phylogenetic relationships in extinct and extant carnivorans,” wrote the authors.