Before dinosaurs walked the Earth, distant mammal relatives with long, serrated canine teeth ruled the land. They existed tens of millions of years before the first mammals appeared. These strange creatures are called gorgonopsians.
They were thought to have lived around 280 million to 270 million years ago and are the oldest saber-toothed animals on record.
Gorgonopsians were not a direct ancestor of living mammals or saber-toothed cats, but they did have some mammal-like characteristics that eventually gave rise to mammals.
The oldest fossilized remains of the animal were recently discovered. The newfound gorgonopsian adds to one of the earliest branches of the wider therapsid group. The finding could shed some light on ancient mammals.
The oldest therapsid fossils are around 270 million years old, but researchers think they evolved 300 million years ago, which means there is a gap in the fossil record. The newly identified gorgonopsian fills that blank space.
Gorgonopsians disappeared around 252 million years ago. Their species ranged in size, with some as small as cats and others as large as polar bears. All of them had serrated canine teeth.
The new gorgonopsian fossils were found on the Spanish island of Mallorca in 2019 and 2021. During the age of the gorgonopsians, the island would have been part of the supercontinent Pangaea.
The remains included skull fragments, dagger-like teeth, jaw bones, ribs, and a hind leg. Based on the bones, the researchers deduced that it was about the size of a dog and weighed 66 to 88 pounds.
Aside from being four-legged and having a tail, the gorgonopsian would not have looked much like a dog. It almost resembles a lizard because it does not have any fur or visible ears. The specimen's skull was incomplete, but it is estimated to measure approximately seven inches long.
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"Although the specimen has a number of features that let us confidently identify it as a gorgonopsian, it is too fragmentary for us to determine if it is definitely a new species or a member of a previously described species," said Kenneth D. Angielcyzk, a co-author of the study.
"If we eventually found a more complete specimen, it would be great to eventually give it a formal species name."
One trait that gorgonopsians share with their mammal cousins is having teeth of different sizes and shapes that all have specific functions.
They seemed to have replaced their teeth throughout their lifetimes, while mammals today only have one replacement cycle of teeth.
The gorgonopsian would have been a predator at the top of the food chain in its day. Previously, gorgonopsian fossils had only been found in dry, arid sites in Russia and South Africa.
Finding the oldest documented gorgonopsian in Mallorca indicates that scientists need to expand their search.
"It's long been thought that the big temporal gap in the therapsid fossil record might correspond to more geographic sampling," said Angielcyzk.
"The fact that Mallorca is a new place for finding therapsids helps to support that idea that we're not necessarily looking in the right places to find the first therapsids."