An international research team has described a new species of Oculudentavis, providing further evidence that the animal first identified as a hummingbird-sized dinosaur was in fact a lizard.
The new species, named Oculudentavis naga in honor of the Naga people of Myanmar and India, is represented by a partial skeleton including a full skull, beautifully preserved in amber with visible scales and soft tissue. The specimen belongs to the same genus as Oculudentavis khaungraae, whose original description as the smallest known bird was retracted last year. Both fossils were found in the same area and are around 99 million years old.
The researchers published their findings in Current biology today (June 14, 2021).
The team, led by Arnau Bolet from the Institut Català de Paleontologia de Barcelona Miquel Crusafont, used CT scans to separate, analyze and numerically compare each bone of the two species, uncovering a number of physical characteristics that identify small animals as lizards. Oculudentavis is so strange, however, it was difficult to categorize it without careful consideration of its characteristics, Bolet said.
“The specimen intrigued us all at first because if it was a lizard, it was a very unusual specimen,” he said in an institutional press release.
Bolet and other lizard experts around the world first noticed the specimen while studying a collection of amber fossils acquired from Myanmar by gemologist Adolf Peretti. (Note: The mining and sale of Burmese amber is often linked to human rights violations. Peretti purchased the fossil legally before the conflict in 2017. More details appear in an ethics statement at the end of this story).
Herpetologist Juan Diego Daza examined the unusual small skull, preserved with a short section of the spine and shoulder bones. He, too, was confused by his odd array of characteristics: could it be some sort of pterodactyl or perhaps a former relative of monitor lizards?
“From the moment we uploaded the first CT scan, everyone was thinking about what it could be,” said Daza, assistant professor of biological sciences at Sam Houston State University. “In the end, a closer look and our analyzes help us clarify its position. “
The main clues that the mysterious animal was a lizard included the presence of scales; teeth attached directly to its jawbone, rather than nestled in sockets like dinosaur teeth were; eye structures and shoulder bones similar to those of a lizard; and a hockey stick shaped skull bone that is universally shared among scale reptiles, also known as squamates.
The team also determined that the skulls of both species had deformed during preservation. The muzzle of Oculudentavis khaungraae was pressed into a narrower, more beak-like profile, while the skull of O. naga – the part of the skull that surrounds the brain – has been compressed. The distortions highlighted bird features in one skull and lizard features in the other, said study co-author Edward Stanley, director of the Museum of Discovery and Digital Dissemination Lab. Florida natural history.
“Imagine taking a lizard and pinching its nose in a triangular shape,” Stanley said. “It would look a lot more like a bird. “
The proportions of Oculudentavis’ bird skull, however, do not indicate that it was related to birds, said study co-author Susan Evans, professor of vertebrate morphology and paleontology at the University. College of London.
“Despite exhibiting a hunched skull and a long, tapered muzzle, it does not exhibit significant physical characters that can be used to maintain a close relationship with birds, and all of its features indicate that it is ‘a lizard,’ she said.
Although the skulls of the two species do not look alike at first glance, their common characteristics became clearer when researchers numerically isolated each bone and compared them to each other. The differences were minimized when the original shape of the two fossils was reconstructed through a painstaking process known as back strain, led by Marta Vidal-García of the University of Calgary in Canada.
“We concluded that the two specimens are similar enough to belong to the same genus, Oculudentavis, but a number of differences suggest they represent separate species,” Bolet said.
In the specimen of O. naga better preserved, the team were also able to identify a raised ridge running down the top of the muzzle and a loose flap of skin under the chin that may have been swollen on display, Evans said. However, the researchers failed in their attempts to find the exact position of Oculudentavis in the lizard family tree.
“He’s a really weird animal. It is unlike any other lizard we have today, ”Daza said. “We think this represents a group of squamates that we weren’t aware of. “
The Cretaceous Period, 145.5 to 66 million years ago, gave birth to many groups of lizards and snakes on the planet today, but trace fossils from this time to their closest Living parents can be difficult, said Daza.
“We believe that many lizards were born around this time, but they still hadn’t evolved into their modern appearance,” he said. “That’s why they can trick us. They may have characteristics of this or that group, but in reality they do not match perfectly.
The majority of the study was conducted with CT data created at the Australian Neutron Scattering Center and the High-Resolution X-ray Tomography facility at the University of Texas at Austin. O. naga is now digitally available to anyone with internet access, allowing the team’s findings to be reassessed and opening up the possibility of new discoveries, Stanley said.
“With paleontology, you often have a specimen of a species to work with, which makes that individual very important. So researchers may be pretty protective of it, but our mindset is ‘let’s get it out there,’ Stanley said. “The important thing is that the research is done, not necessarily that we do the research. We think this is how it should be.
While Myanmar’s amber deposits are a treasure trove of fossil lizards found nowhere else in the world, Daza said the consensus among paleontologists is that acquiring Burmese amber ethically is became increasingly difficult, especially after the military took control in February.
“As scientists, we believe it is our duty to uncover these invaluable traces of life, so that the whole world can learn more about the past. But we have to be extremely careful that during the process we do not benefit a group of people who commit crimes against humanity, ”he said. “Ultimately, the credit goes to the miners who risk their lives to recover these incredible amber fossils. “
The other co-authors of the study are J. Salvador Arias of the National Council for Scientific and Technical Research of Argentina (CONICET – Miguel Lillo Foundation); Andrej Cernansky from Comenius University in Bratislava, Slovakia; Aaron Bauer from the University of Villanova; Joseph Bevitt of the Australian Organization for Nuclear Science and Technology; and Adolf Peretti from the Peretti Museum Foundation in Switzerland.
A 3D scanned specimen of O. naga is available online through MorphoSource. The fossil of O. naga is kept at the Peretti Museum Foundation in Switzerland, and the specimen of O. khaungraae can be found at the Hupoge Amber museum in China.
The specimen was acquired following the ethical guidelines for the use of Burmese amber set out by the Society for Vertebrate Paleontology. The specimen was purchased from authorized companies independent of military groups. These companies legally export Myanmar amber coins, following an ethical code that ensures that no human rights violations have been committed during mining and marketing and that money from sales is made. did not support the armed conflict. The fossil has an authenticated paper trail, including export permits from Myanmar. All documentation is available on request from the Peretti Museum Foundation.
Reference: June 14, 2021, Current biology.
DOI : 10.1016/j.cub.2021.05.040
Funding: National Science Foundation, Sam Houston State University, Royal Society, Spanish Ministry of Science, Innovation and Universities, CERCA / Generalitat de Catalunya Program, Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences