Near the Brazilian municipality of São Francisco de Assis, in a Triassic rock exposure, a pristine 115 mm-long skull was found. Sharp, dagger-like teeth shoot out the maw of the ancient creature. The find represents the most complete tetrapod fossil ever found from the Lower Triassic of South America.
“It is unusual to find such well-preserved fossil skulls, although there are other examples known from around the world,” Richard Butler, of the Univ. of Birmingham’s School of Geography, Earth and Environmental Sciences, told R&D Magazine.
“Generally for fossils to be well-preserved they need to be buried with sediment soon after the animal’s death. If skulls and skeletons aren’t buried rapidly they tend to break up and disintegrate as the animal decays and scavengers eat it,” Butler added.
The fossil skull in question belonged to ancient lizard species Teyujagua paradoxa. It was the subject of a study published last week in Scientific Reports.
Though not involved in the initial 2015 discovery, Butler later became involved in the study.
The fossil was discovered by a team from the Paleobiology Laboratory of the Universidade Federal do Pampa.
Teyujagua represents a transitional species. Its anatomy is a mix between older primitive reptiles and archosauriforms, a diverse group that included all the dinosaurs and pterosaurs, and modern birds and crocodiles.
According to the researchers, Teyujagua lived after the Permo-Triassic mass extinction, which happened around 252 million years ago. The event was a major overhaul of ecosystems. Some estimates pin the species die-off around 96 percent. In the wake of whatever disaster befell the planet, Teyujagua picked up the pieces and proliferated.
“The discovery of Teyujagua was really exciting,” said Felipe Pinheiro, the study’s lead author, in a statement. “Ever since we saw that beautiful skull for the first time in the field, still mostly covered by rock, we knew we had something extraordinary in our hands. Back in the lab, after exposing the bones, the fossil exceeded our expectations. It had a combination of features never seen before, indicating the unique position of Teyujagua in the evolutionary tree of an important group of vertebrates.”
The species was named after the mythological beast Teyú Yaguá, whose name translates to “fierce lizard.” The mythological creature is typically represented as a dog-headed lizard. It comes from the mythology of the Guarani ethnic group, which occupied portions of central east South America, according to the researchers.
Based on the skull, the researchers believe Teyujagua grew to around 1.5 m in length. It was likely semi-aquatic due to the positioning of its nostrils atop its snout. Probably, it traversed the lands nearby lakes and rivers.
This window into a primordial world is precisely what spurred Butler’s interest in paleontology. “I was excited by the opportunities to discover these amazing extinct animals and vanished worlds that no-one else had ever previously laid eyes on,” he said.
The site where the skull was found is currently still under investigation, according to the Univ. of Birmingham.