Some 100 million years ago in a seaside mangrove swamp in what we humans now call Myanmar, a truly bizarre dinosaur flitted about, stalking its insect prey. Its head was just a half-inch long, making it smaller than the smallest living bird, the bee hummingbird. Its mouth was packed with needle teeth, which hung over its lower beak, giving it a bit of a derpy vibe. For a bird-like predatory dinosaur, its eyes were oddly positioned on the sides of its head, meaning it probably didn’t have binocular vision.
The tiny flying dino snagged a bug here, and snagged a bug there. Then it perished somehow. And luckily for paleontologists, it got covered in sap that hardened into amber, preserving its skull in incredible detail. But despite it being a speck among its lumbering dinosaur peers, it has persisted on through the ages. Now that it has been unearthed by a team of paleontologists, it’s giving them tantalizing clues to how it lived the most miniature of lives.
It’s also raising a lot of questions, because, in technical terms, it’s also just … weird. “It just has morphologies that are all over the place, and also has morphologies that are unlike any bird or dinosaur at all,” says paleontologist Jingmai O’Connor of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, who coauthored a new paper describing the specimen in the journal Nature. “Because it’s so weird and because we only have a skull, it’s really difficult to understand. It’s this really weird evolutionary puzzle.”
Let’s try to put some pieces together. To begin with, O’Connor and her colleagues had to make sure the specimen wasn’t so small simply because it was a baby. “Only irresponsible paleontologists name species from juveniles,” O’Connor says. “The morphology is going to change.” If you think about human babies, for example, we start out with disproportionately large heads and eyes. We end up growing into them. But an important clue about this new dinosaur was that the bones of its skull were fused together when it died. (As with humans, some species are born with skulls that are not fully joined in infancy, allowing the brain to grow. The skull later fuses around it.) So here was proof that the new dino was an exceedingly tiny adult, not a baby.
Another piece of the puzzle was that tooth-packed beak. Modern birds lack teeth, of course, because of an evolutionary quirk of their lineage. In the time of the dinosaurs, the Cretaceous period, there were many bird lineages with all kinds of different teeth. But the one that gave rise to modern birds didn’t have them, so chickens and ostriches lack them as well—even species like falcons that eat meat. Fish-eating birds, though, tend to have hook-like projections in their mouths that help them hold on to their wiggling prey. “You can just Google search ‘penguin mouth,’ and it’s really gross and weird,” says O’Connor.