Jaw canals reveal dog-sized reptile to be the earliest venomous land vertebrate
Since its discovery in the 1930s, questions have remained over whether or not the Euchambersia, a dog-sized pre-mammalian reptile that lived in South Africa, was venomous. If so, its existence 260 million years ago would make it the earliest known venomous land vertebrae, pre-dating snakes by around 100 million years. South African researchers are claiming to have ended the debate once and for all, with new CT scans of Euchambersia fossils revealing it did in fact have anatomical features designed for venom production.
Scientists had suspected that Euchambersia produced venom because of strange features on its jaw that appeared to be indicative of a venom gland. But as recently as September last year, researchers cast doubt on these assumptions, arguing that they were based on inaccurate drawings of the creature's canine tooth.
Among the skeptics was Julian Benoit, a paleontologist at South Africa's University of the Witwatersrand. And now, he has gone about finding some answers. Complicating things was the fact that venom glands don't fossilize, but armed with new CT scanning and 3D-imaging technologies, Benoit and his team analyzed two fossilized Euchambersia skulls, the only two every found, to fill in the blanks. And what they found were anatomical adaptations they say are indeed 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," says Benoit. "Moreover, 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 prey."
This composition led the researchers to conclude that Euchambersia's venom flowed into its mouth and was used to kill prey indirectly by being introduced through ridges on the outside of its canine teeth. This is different to how snakes and cobras inject prey directly by introducing venom through needle-like grooves in their teeth.
The researchers believe Euchambersia, which measured between 40 and 50 cm (16 and 20 in) long, probably used the venom for hunting and to stave off predators such as saber-toothed carnivores. What makes the finding even more interesting is the fact that the creature is related to early mammals, rather than 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," says Benoit. "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."
The team published their work in the journal PlosOne.
Source: University of the Witwatersrand