Venom may have first evolved in mammals 260 million years ago

Scientists have identified the oldest ever venomous vertebrate from a 260 million-year-old fossil of a dog-sized animal that produced a deadly cocktail of venoms long before the very first snake was born.
Living in the Karoo, near Colesberg in South Africa, the therapsid Euchambersia developed a deep and circular fossa, just behind its canine teeth in the upper jaw, in which a deadly venomous cocktail was produced and delivered into the mouth through a fine network of bony grooves and canals.
Euchambersia is related to early mammals, not snakes.
"This is the first evidence of the oldest venomous vertebrate ever found, and what is even more surprising is that it is not in a species that we expected it to be," said Julien Benoit, researcher at the University of the Witwatersrand in South Africa.

"Today, snakes are notorious for their venomous bite, but their fossil record vanishes in the depth of geological times at about 167 million years ago, so, at 260 million years ago, the Euchambersia evolved venom more than a 100 million years before the very first snake was even born," said Benoit.
As venom glands do not fossilise, researchers used cutting edge CT scanning and 3D imagery techniques to analyse the only two fossilised skulls of the Euchambersia ever found and discovered stunning anatomical adaptions that are compatible with venom production.

"First, a wide, deep and circular fossa (a space in the skull) to accommodate a venom gland was present on the upper jaw and was connected to the canine and the mouth by a fine network of bony grooves and canals," said Benoit.

"We discovered previously undescribed teeth hidden in the vicinity of the bones and rock: two incisors with preserved crowns and a pair of large canines, that all had a sharp ridge. Such a ridged dentition would have helped the injection of venom inside a prey," he said.
Unlike snakes like vipers or cobras, which actively inject their prey with venom through needle-like grooves in their teeth, the Euchambersia's venom flowed directly into its mouth, and the venom was passively introduced into its victim through ridges on the outside of its canine teeth.
"Echambersia could have used its venom for either protection or hunting. Most venomous species today use their venom for hunting, so this is a much more probable option," said Benoit.

"Added to that, not all animals at the times were insectovorous, particularly therapsids, which was very diverse," he said.
The first Euchambersia fossil was found in 1932, and the second in 1966.
According to measurements of the two fossils, the Euchambersia was a small dog-like pre-mammalian reptile that grew between 40 and 50 cm long, and lived well before the first dinosaur even appeared.
Researchers believe that mammals that lived millions of years ago used to be venomous, but lost this ability in time.
The study was published in the journal Plos One.