Hidden in amber are miniature dinosaurs the size of hummingbirds

A piece of amber less than 4 centimeters wide contains the complete skull of the Oculudentavis khaungraae

A piece of amber less than 4 centimeters wide contains the complete skull of the Oculudentavis khaungraae. This newly discovered dinosaur lived in Myanmar 9900 million years ago

The small phylloscopic dinosaur Oculudentavis khaungraae may have preyed on insects in the Cretaceous rainforest.

The March issue of nature describes the fossil, which is only 1.5 centimeters long from the hindbrain to the tip of the beak, about the width of a thumb nail. The proportions of the skull suggest that the animal was about the size of a bee hummingbird, meaning the newly discovered dinosaur might have been lighter than a round coin.

This miniature creature appears to be closely related to covert dinosaurs such as Archaeopteryx and Jeholornis, both of which are distant relatives of modern birds. The researchers speculated that the small dinosaur had the same covert wings as these animals, but they could not presume its ability to fly in the absence of more fossils.

Although this dinosaur is similar in proportion to hummingbirds, it does not eat nectar. Its upper jaw has 40 sharp teeth, and its large eyes—suitable for locking prey among the leaves—have features not seen in other dinosaurs. This creature has a suitable genus called Oculudentavis, which is taken from the Latin word for eye, tooth and bird.

There is no living creature whose body structure is similar to that of the bird with the eyetooth. "It presents a completely different ecological location that we never knew existed," said study co-author Jingmai O'Connor, a paleontologist at the Chinese Institute of Vertebrate Paleontology and Paleoanthropology. "It's funny, but it's also a complete mystery, and everything about it is weird."

"This is truly one of the rarest and most amazing discoveries!" Paleontologist Renne of the University of South Florida. Ryan Carney said in an email that he was not involved in the study. "Like catching Cretaceous lightning into a bottle, this piece of amber preserves an unprecedented snapshot of miniature dinosaur skulls with exciting new features."

Sharp-toothed beak

When Xing Lida first saw the fossil, he thought to himself, "It's so strange." The paleontologist at the China University of Geosciences, the first author of the new study, thought at the time that the animal's long-billed beak and larger eyes showed that he was an early bird. But Xing Lida was surprised by the number of teeth it had, which seemed to be more than any Cretaceous toothed bird. A total of 23 teeth, each less than half a centimeter long, were nailed to the creature's right upper jaw.

To examine the skull carefully, Xing Lide brought the amber to a high-energy X-ray mechanism in Shanghai to scan for structural features similar to the width of the red blood cells. He then sent the scans to Zou Jingmei, who specializes in dinosaurs related to birds, who was stunned by what he saw.

"This (fossil) is so pristine and so well preserved," Ms. Zou said. "This thing is super perfect."

To figure out the dinosaur's relative age, Zou and her colleagues pored over X-rays of the skull and examined its bone closures, an indicator of the animal's maturity. The researchers concluded that the bird was or nearly an adult when it died — making its miniature size even more unique.

Eyes that are different from the birds

This unusual creature also has eyes large enough to protrude from the outside of the head. Confused, Zou Jingmei decided to contact the "eye man" Lars in the paleontological community. Lars Schmitz, the W..M. Keck Science Department.M in California, USA. Keck Science Department) researchers study the evolution of vision.

When Schmidt first saw these skull scans, he understood that the eyes resembled the large, proportional eyes of small birds, a feature that reinforced the hypothesis that the fossils of the bird of the tooth were adults.

The eyes of both reptiles and birds have several small bone rings to help support the organs of vision. These bone rings form a bone disc shaped like a narrow rectangle, but these small bones on the eye-toothed bird are shaped like ice cream spoons. "The shapes you see here don't really appear in any other bird or any other dinosaur," Schmidz said.

The only animals that now have similar spoon-shaped eye bones are the heliotropic lizards. What researchers now know is that the eye-toothed bird uses its particularly large eyes to forage during the day, catching insects with its toothed beak.

Probably the most similar bird now is the short-tailed bird, a small bird in the Caribbean that feeds on insects, Jayne. Says Jen Bright, a biologist at the University of Hull who studies bird skulls. But the skull of the short-tailed bird is twice as large as the fossil of the bird with the eye tooth. "It's pretty shocking to find such a small vertebrate fossil," he says. "It's such a freak, I love it!" Eyes that are different from the birds

Probably the most similar bird now is the short-tailed bird, a small bird in the Caribbean that feeds on insects, Jayne. Says Jen Bright, a biologist at the University of Hull who studies bird skulls. But the skull of the short-tailed bird is twice as large as the fossil of the bird with the eye tooth. "It's pretty shocking to find such a small vertebrate fossil," he says. "It's such a freak, I love it!"

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Zou Jingmei speculated that the singular characteristics of the eye-toothed bird may have developed in the unique prehistoric environment in which it lived. In resource-limited ecosystems such as islands, evolution may have pushed animals toward miniaturization, while the remains of marine animals such as ammonite show that Burmese amber deposits formed along the islands or at least off the coast.

"The smallest vertebrates that live are a few small frogs in Madagascar, and they are predators, just like the eye-toothed birds we assume," Ms. Zou said.

Excavating fossils – and controversy

The eye-toothed bird first appeared in 2016, when Burmese amber collector Khaung Ra obtained two specimens from a mine, including this tiny mysterious skull. Kuan Ya donated the fossil to the Amber Pavilion Museum in Tengchong, China, hosted by his son-in-law Chen Guang. The species name of this dinosaur is called Khaungraae in recognition of his donation.

The fossil is the latest discovery in an amber mine in northern Myanmar, where the massive amount of amber unearthed here preserves some of the tiniest remains of an ancient rainforest. In recent years, paleontologists have found the remains of several species of insects buried in amber, a snake and even part of a covert-feathered dinosaur. No scientist has contributed more than Xing Lida in the cause of collating and documenting these ambers, and his research is partly sponsored by the National Geographic Society.

As the scientific value of Burmese amber rises, so do ethical concerns about the study. Many important amber fossils were initially in the hands of private collectors, making the accessibility of these specimens to future scientists questionable. Miners also face unsafe working conditions, and the mine is located in the northern Myanmar state of Kachin, where clashes between the Burmese army and the Kachin independence rebels have been raging for a long time. According to the Kachin Development Networking Group, the 2018 attempt by government forces to occupy the mining area resulted in the displacement of thousands of Kachin indigenous people.

According to Xing, the Amber Court Museum is about to build a museum in Myanmar, and Xing and other scholars are trying to wait for amber specimens to be returned to Myanmar once the conflict in the area subsides, thus ensuring that amber is available for scientific research. "It would be great if these important amber (fossils) could be left in the country where they were found," he wrote in an email.

While the return of Burmese amber continues, scientists will continue to search for more fossils of the bird. Xing Lida had already heard rumors about the lost link. The amber containing the skull of the bird was rumored to have come from a larger piece of amber with preserved feathers, but when Xing Lida saw the skull, the two pieces of amber had been separated, cut and polished, making it impossible for him to confirm that the two pieces of amber came from the same source.

Schmidz was one of those people fascinated by this possibility. "Oh, I can't describe it!" He said. "This skull is so weird... Who knows what else to find besides the parts we've already described?"