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Skull of Smallest Known Dinosaur Found in 99-Million-Year Old Amber

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Skull of Smallest Known Dinosaur Found in 99-Million-Year Old Amber
The piece of amber measures only 1.25 inches (31.5 millimeters) in length. The skull is a mere 0.6 inches (11 millimeters). Xing Lida / CC BY-ND

By Lars Schmitz, Jingmai Kathleen O'Connor

Editor's Note from The Conversation, July 28, 2020: This article was based on a study published in the peer-reviewed journal Nature on March 11, 2020. On July 22, 2020, the journal retracted the article after other researchers raised concerns that the skull belonged to a lizard, not a bird. Here is the retraction note from the paper's authors: "We, the authors, are retracting this Article to prevent inaccurate information from remaining in the literature. Although the description of Oculudentavis khaungraae remains accurate, a new unpublished specimen casts doubts upon our hypothesis regarding the phylogenetic position of HPG-15-3."

In 2016, our colleague Xing Lida held up a small piece of polished, deeply yellow amber. As sunlight shone through the ancient resin, Lida saw the outline of a pristinely preserved, amazingly small skull. There was a prominent eye socket, a dome-shaped crown of the head, a long, tapering snout and even small teeth. It was bird-like, but in a strange and ancient way.


The amber contains the skull of Oculudentavis khaungraae, a newly described dinosaur and one of the smallest ever discovered. Its tiny stature is forcing paleontologists to rethink the lower limits of body size in birds, and the nearly 100-million-year-old fossil is challenging the current understanding of when and how dinosaur giants shrank into the birds of today.

A Mysterious Transformation

Tiny Oculudentavis may have occupied a unique ecological niche in the ancient world. Han Zhixin / CC BY-ND

The evolutionary transition of dinosaurs to modern birds is one of the most astounding transformations in the history of life: large, bipedal and mostly carnivorous dinosaurs morphed into small, flying birds. Famous discoveries like Archaeopteryx and more recently the fossils from the Jehol Biota in China have given researchers some hints about the process. But finds from this evolutionary phase — which researchers think began about 200 million years ago — are rare.

Paleontologists are far from having a complete picture of the evolution of birds, and even farther from a full inventory of Earth's ecosystems in the age of dinosaurs. Our research on the tiny Oculudentavis, published in the journal Nature, adds valuable information to the puzzle of when, how and to what extent dinosaurs shrank.

Clues in Bone

This high-resolution scan allowed us to see the intricacies of a bone structure unlike any before seen in birds or dinosaurs. Xing Lida / CC BY-ND

Our team needed to see the minute details of the skull, and we needed to do it without cracking or ruining the specimen - a difficult task with a skull encased in 99-million-year old amber from Myanmar. To do that, we scanned the skull with high-resolution X-rays and created a digital model with very fine anatomical detail. What emerged was a picture of an overall bird-like anatomy. But in some interesting ways, Oculudentavis is unlike any bird or dinosaur that has ever been found.

The obvious curiosity of the fossil is its size: Oculudentavis rivaled the smallest bird living today, the bee hummingbird, and likely was no more than 1.6 inches (4 centimeters) from beak to tail. We considered whether the skull possibly belonged to a very young animal, but the extent and pattern of bone growth and the proportional size of the eye pointed to a mature bird.

With a total skull length of just about 0.6 inches (1.5 centimeters), Oculudentavis pushes against what is considered the lower limit of size in birds: the head still had to hold functional eyes, a brain and jaws. The small size is especially surprising if one considers that Oculudentavis lived during the same time as giant plant-eating dinosaurs like Argentinosaurus.

Small and Specialized

The small size of Oculudentavis is striking, but to a trained eye there are other extremely unusual features, too.

First of all, the skull seems to be built for strength. The bones show an unusual pattern of fusion and the skull lacks an antorbital fenestra, a small hole often found in front of the eye.

The eyes of Oculudentavis also surprised us. The shape of the bones found within the eye, the scleral ossicles, suggests that it probably had conical eyes with small pupils. This type of eye structure is especially well adapted for moving around in bright light. While daytime activity might be expected for an ancient bird from the age of dinosaurs, the shape of the ossicles is entirely distinct from any other dinosaur and resembles those of modern-day lizards.

Adding to the list of unexpected features, the upper jaw carries at least 23 small teeth. These teeth extend all the way back beneath the eye and are not set in deep pockets, an unusual arrangement for most ancient birds. The large number of teeth and their sharp cutting edges suggest that Oculudentavis was a predator that may have fed on small bugs.

The sum of these traits — a strong skull, good eyesight and a hunter's set of teeth — suggests to us that Oculudentavis led a life previously unknown among ancient birds: it was a hummingbird-sized daytime predator.

One of the Earliest and Tiniest Birds?

Placing Oculudentavis in the tree of life is, given its strange anatomy, challenging. Our phylogenetic analysis — the investigation of its relationships to other dinosaurs — identifies Oculudentavis as one of the most ancient birds. Only Archaeopteryx branched off earlier.

Scientists consider the nectar-feeding hummingbirds — which appeared 30 million years ago — the smallest dinosaurs on record. But if our placement of Oculudentavis holds true, the miniaturization of dinosaurs may have peaked far earlier than paleontologists previously thought. In fact, the largest and the smallest dinosaurs may have walked and flown the same earth nearly 100 million years ago.

Our work demonstrates how little scientists know about the little things in the history of life. Scientists' snapshot of fossil ecosystems in the dinosaur age is incomplete and leaves so many questions unanswered. But paleontologists are eager to take on these questions. What other tiny species were out there? What was their ecological function? Was Oculudentavis the only visually guided bug hunter? To better understand the evolution of the diversity of life we need more emphasis and recognition of the small.

Amber holds strong potential to fill that gap. Maybe one day a scientist will hold up another piece, and let sunshine reveal a complete Oculudentavis, or even a previously unknown species. More finds in amber will help illuminate the world of the tiny vertebrates in the age of dinosaurs.

Reposted with permission from The Conversation.

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In early October, Britain's Prince William teamed up with conservationist David Attenborough to launch the Earthshot Prize, a new award for environmentalist innovation. The Earthshot brands itself the "most prestigious global environment prize in history."

The world-famous wildlife broadcaster and his royal sidekick appear to have played an active role in the prize's inception, and media coverage has focused largely on them as the faces of the campaign.

But the pair are only the frontmen of a much larger movement which has been in development for several years. In addition to a panel of experts who will decide on the winners, the prize's formation took advice from the World Wildlife Fund, Greenpeace and the Jack Ma Foundation.

With more and more global attention on the climate crisis, celebrity endorsement of environmental causes has become more common. But why do environmental causes recruit famous faces for their campaigns? And what difference can it make?

'Count Me In'

"We need celebrities to reach those people who we cannot reach ourselves," says Sarah Marchildon from the United Nations Climate Change secretariat (UNFCCC) in Bonn, Germany.

Marchildon is a proponent of the use of celebrities to raise awareness of environmental causes. In addition to promoting a selection of climate ambassadors who represent the UN on sustainability issues, Marchildon's team has produced videos with well-known narrators from the entertainment world: among them, Morgan Freeman and Mark Ruffalo.

"We choose celebrities who have a lifestyle where they are already talking about these issues," Marchildon explains.

"Sometimes they reach out to us themselves, as David Attenborough did recently. And then they can promote the videos on their own social channels which reach more people than we do — for example, if they have 20 million followers and we have 750,000."

Environmental groups focused on their own domestic markets are also taking this approach. One Germany-based organization that uses celebrities in campaigns is the German Zero NGO. Set up in 2019, it advocates for a climate-neutral Germany by 2035.

German Zero produced a video in March 2020 introducing the campaign with "66 celebrities" that supported the campaign, among them Deutschland 83 actor Jonas Nay and former professional footballer Andre Schürrle. They solicit support as well as financial contributions from viewers.

"Count me in," they say, pointing toward the camera. "You too?"

"We are incredibly grateful for the VIPs in our videos," says German Zero spokeswoman Eva-Maria McCormack.

Assessing Success Is Complex

But quantifying the effectiveness of celebrity endorsement of campaigns is not a straightforward process.

"In order to measure effectiveness, first of all you need to define what is meant by success," says Alegria Olmedo, a researcher at the Zoology Department at the University of Oxford.

Olmedo is the author of a study looking at a range of campaigns concerning pangolin consumption, fronted by local and Western celebrities, in Vietnam and China. But she says her biggest stumbling block was knowing how to measure a campaign's success.

"You need a clear theory of change," explains Olmedo. "Have the celebrities actually helped in achieving the campaign's goals? And how do you quantify these goals? Maybe it is increased donations or higher engagement with a cause."

A popular campaign in China in recent years saw famous chefs Zhao Danian and Shu Yi pledge to abstain from cooking endangered wildlife. While the pledge achieved widespread recognition, both Olmedo and Marchildon say it's difficult to know whether it made any difference to people's actions.

"In life we see a thousand messages every day, and it is very hard to pinpoint whether one campaign has actually made a difference in people's behavior," she explains.

Awareness Is Not Enough

Many campaigns that feature celebrities focus on raising awareness rather than on concrete action — which, for researcher Olmedo, raises a further problem in identifying effectiveness.

"Reach should never be a success outcome," she says. "Many campaigns say they reached a certain number of people on social media. But there has been a lot of research that shows that simply giving people information does not mean they are actually going to remember it or act upon it."

But anecdotal evidence from campaigns may suggest reach can make an active difference.

"Our VIP video is by far the most watched on our social media channels," McCormack from German Zero says. "People respond to it very directly. A lot of volunteers of all ages heard about us through that video."

However, some marketing studies have shown that celebrity endorsement of a cause or product can distract from the issue itself, as people only remember the person, not the content of what they were saying.

Choosing the Right Celebrity

Celebrity choice is also very important. Campaigns that use famous faces are often aiming to appeal to members of the public who do not necessarily follow green issues.

For certain campaigns with clear target audiences, choosing a climate scientist or well-known environmentalist rather than a celebrity could be more appealing — Attenborough is a classic example. For others, images and videos involving cute animals may be more likely to get a message heard than attaching a famous face.

"We choose celebrities who have a lifestyle where they are already talking about these issues," says Marchildon from the UN. "You need figures with credibility."

McCormack cites the example of Katharine Hayhoe, an environmental scientist who is also an evangelical Christian. In the southern United States, Hayhoe has become a celebrity in her own right, appealing to an audience that might not normally be interested in the messages of climate scientists.

But as soon as you get a celebrity involved, campaigns also put themselves at risk of the whims of that celebrity. Prince William and younger members of the royal family have come under fire in recent years for alleged hypocrisy for their backing of environmental campaigns while simultaneously using private jets to fly around the world.

But Does It Really Work?

While environmental campaigns hope that endorsement from well-known figures can boost a campaign, there is little research to back this up.

"The biggest finding [from my study] was that we were unable to produce any evidence that shows that celebrity endorsement of environmental causes makes any difference," says Olmedo.

This will come as a blow to many campaigns that have invested time and effort into relationships with celebrity ambassadors. But for many, the personal message that many celebrities offer in videos like that produced by German Zero and campaigns like the Earthshot Prize are what counts.

The research may not prove this conclusively — but if the public believes a person they respect deeply personally cares about an important issue, they are perhaps more likely to care too.

"I personally believe in the power this can have," says Marchildon. "And if having a celebrity involved can get a single 16-year-old future leader thinking about environmentalist issues — that is enough."

Reposted with permission from DW.

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