Newly Discovered 250-Million-Year-Old Fierce Lizard Fossil is Named After Mythical Monster

Ancient Origins

Who knows if the people who lived in the Paraná Basin of southern Brazil years ago saw fossils of dinosaurs and came up with strange mythical beings because of them. Whatever connection there may be, scientists have identified a new fossil near where the Guarani people live—a beautiful fossil of a creature that fills an evolutionary gap.

The previously unknown lizard lived about 250 million years ago.
The scientists have named the genus of the creature after one of the Guarani people’s mythical monsters. An article in the journal Nature states:

“Genus named after Teyú Yaguá, one of the seven legendary beasts in the mythology of the Guarani ethnic group, who occupied a large territory of central east South America, including the type locality of the new species. Teyú Yaguá, literally meaning ‘fierce lizard,’ is commonly represented as a dog-headed lizard. Species name derived from paradoxa, Greek meaning ‘paradoxical’, ‘unexpected’, owing to its unusual combination of plesiomorphic and derived characters.”

Teyujagua paradoxa holotype. (Pinheiro et al.)

The team who found it, three Brazilian university researchers, call it a beautiful fossil. It was a small animal, similar to a crocodile. It likely lived near lakeshores and fed on fish.
An article on Guarani mythology describes the monster called Teyú Yaguá and says it is a giant lizard with a dog’s head and skin covered in gold and precious stones that it gained from rolling in the treasures of Itayu.
His eyes are believed to shoot fire, but despite this and his menacing appearance, he is said to be benign. He doesn’t move well, but that may be due to his large size.

Depiction of Teyú Yaguá from the Mythical Museum Ramón Elías. (tripfreakz)

According to legends, Teyú Yaguá’s diet consists of fruit, and he is considered the protector of fruits. But his favorite food is honey, which his brother Yasy Yatere, another monster, gave him.

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Not knowing about evolution led many people around the world to tell stories about how the world and its various creatures and features came into being. The Guarani believed that Teyú Yaguá was the son of Tau, the spirit of evil, and Kerana, a Guarani princess.
The couple’s story is highly important in the Guarani creation myth and belief system. Tau took form as a human and courted Kerana for seven days.

Depiction of Tau and Kerana. (Public Domain)

But the spirit of good, Angatupyry, tried to save Kerana. Angatypyry fought Tau for seven days until he defeated him. Tau went into exile. But he returned, kidnapped Kerana, and they became a couple. The goddess Arasy cursed the couple. With this curse and Tau’s malevolent nature, the pair had seven monstrous sons with different attributes and domains. Teyú Yaguá is one of these seven sons.
The fossil identified by the scientists from Brazilian universities was related to the dinosaurs’ ancestors the archosauriforms—a class of reptiles that were at the apex of the food chain before a series of volcanic eruptions nearly wiped them out about 252 million years ago. About 90 percent of Earth’s life forms that lived then were killed by the catastrophe.

Fossilized skull of the Teyujagua. (University of Birmingham)

Felipe Pinheiro of the Universidade Federal do Pampa was one of the scientists who discovered the fossil skull near the city of São Francisco de Assis.

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He said the creature differs from other fossils of the Lower Jurassic. It is similar in anatomy to the archosauriforms and primitive reptiles, including the dinosaurs and pterosaurs, modern birds and crocodiles.
"The discovery of Teyujagua was really exciting,” Pinheiro told the BBC. “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 slowly 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.”

Archosauromorph phylogeny showing the recovered position of Teyujagua. (Pinheiro et al.)

The ancient culture of the Guarani people, who are spread across Paraguay, Brazil, Argentina, and Bolivia, is as strong today as it was many centuries ago, sustained through an oral tradition of passing down myths and legends from one generation to the next.
Featured Image: Artistic representation of Teyujagua paradoxa. Source: Voltaire Neto
By Mark Miller

Dinosaur Arms to Bird Wings: It's All in the Wrist

by Stuart Gary

One of the last niggling doubts about the link between dinosaurs and birds may be settled by a new study that shows how bird wrists evolved from those of their dinosaur predecessors.
The study, reported in the Journal PLOS Biology, shows how nine dinosaurian wrist bones were reduced over millions of years of evolution to just four wrist bones in modern day birds.
"This discovery clarifies how dinosaur arms became bird wings," said one of the study's authors, Dr Alexander Vargas of the University of Chile in Santiago.

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"It shows that some bones fused, other bones disappeared, and one bone disappeared and then reappeared in evolution."
Skeletal similarities between theropod dinosaurs and birds provide some of the strongest evidence showing how birds developed from dinosaurs. But the evolution of straight dinosaur wrists into hyperflexible wrists allowing birds to fold their wings when not flying, has remained a point of contention between palaeontologists and some developmental biologists.
Among the structures in question is a half-moon shaped wrist bone called the semilunate which is found in dinosaurs and looks very similar to a wrist bone also found in birds.
The semilunate originated as two separate dinosaur bones which eventually fused into a single bone. However some developmental biologists claim it evolved as a single bone in birds, and so isn't the same bone as that found in dinosaurs.
To help settle the debate, Vargas and colleagues examined the wrist bones of dinosaur fossils in the collections from several museums, and compared them to new developmental data from seven different species of modern birds.
"We developed a new technique called whole-mount immunostaining, which allows us to observe skeleton development better than ever before, including the expression of proteins inside embryonic cartilage," said Vargas.

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The technique allowed the authors to determine that the embryonic semilunate in birds evolves as two separate cartilages which fuse into a single bone, consistent with what palaeontologists had been saying.
"These findings eliminate persistent doubts that existed over exactly how the bones of the wrist evolved, and iron out arguments about wrist development being incompatible with birds originating from dinosaurs," said Vargas.
The study also produced an interesting surprise for the research team when they discovered a wrist bone called the pisiform, which was present in early sauropod (four-legged, long-tailed, long-necked) dinosaurs, but had disappeared in later theropod (two-legged, two-armed) dinosaurs.
The authors found the pisiform had reappeared in early birds, probably as an adaptation for flight, where it allows transmission of force on the downstroke while restricting flexibility on the upstroke.
"We think the pisiform was lost when dinosaurs became bipedal," said Vargas. "Quadrupedal animals used this bone because they walk with their forelimbs, but bipedal dinosaurs no longer walked with their forelimbs and lost the bone. However they regained it when they began using their forelimbs for locomotion in flight."

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This is a compelling scenario for a rare case of evolutionary reversal, said Professor Mike Archer of the University of New South Wales, who was not involved in the study.
"That's the most fascinating thing coming out of this work, because all of a sudden we're understanding how complex and yet how flexible and deliciously plastic embryological development can be," said Archer.
"There may be a gene lying around dormant and doing nothing, which suddenly gets kick-started and produces a structure that had been lost in the ancestor of the same animal."
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