99 million years ago, the skull of a tiny bird with lizard teeth and eyes was trapped in amber. Their discovery in northern Burma allows a new species of dinosaur to be described, the smallest from the Mesozoic era, which rivals the smallest living modern bird, the hummingbird.
The discovery of fossil remains of soft tissue and even the skeletons of tiny fauna is very rare, due to the delicate and small size of these animals. However, exceptionally these tiny individuals, some from the age of dinosaurs, are preserved for millions of years in amber.
This is the case of a small dinosaur similar to a current hummingbird, but with lizard teeth and eyes, called Oculudentavis khaungraae. His skull, discovered two years ago in the amber mining mines in northern Burma, was trapped about 99 million years ago in the resin.
A study, published today in the journal Nature, now describes this new species of dinosaur, the smallest in the world to date. With a skull, only 7.1 mm long, O. khaungraae was similar in size to the smallest living bird, the black-tailed hummingbird or flying bird.
“The skull belonged to a very primitive bird. Because birds are dinosaurs, the new fossil was interpreted as a bird and a dinosaur, “explains Luis M. Chiappe, a researcher at the Los Angeles County Museum of Natural History in the US.
A dinosaur-bird that lived in isolation
This finding in amber provides scientists with unprecedented information, especially about the smallest animals whose remains are not represented in the fossil record. “It is very relevant how this discovery highlights the importance of amber deposits to reveal a hidden diversity of small animals,” says Chiappe.
“It was daytime, he probably ate insects and lived in the trees,” says the expert.
The well-preserved remains of O. khaungraae have allowed the research team, led by Jingmai O’Connor of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing (China), to learn in this way about the lifestyle of the tiny animal. “It was daytime, probably ate insects and lived in the trees,” says the expert.
The eye socket was large, similar to that of a lizard. According to the researchers, it also had a narrow opening that only let in a small amount of light, so they deduce that the animal must be active during the day.
But one of the most striking features is the presence of about 29 or 30 teeth in his jaw. Despite its diminutive size, this suggests that it was a predator and probably fed on small arthropods or invertebrates, unlike modern birds of similar size, which do not have teeth and feed on nectar.
Finally, its diminutive size could arise from living in isolated environments, although the ecology in which it lived is unknown. According to the authors, this amber formed on an island within the Trans-Tethyan arc, an area where India collided with Asia.
Lida Xing et al. “Hummingbird-sized dinosaur from the Cretaceous period of Myanmar” Nature March 11, 2020