Scientists say they've discovered the smallest known dinosaur which, at an estimated 2 grams, was roughly "the weight of two dollar bills," per Live Science. The skull of the new birdlike species, about the size of the smallest hummingbird on Earth today, was found in a 99-million-year-old, pebble-sized chunk of amber pulled from a mine in northern Myanmar, reports the BBC. The species, dubbed Oculudentavis khaungraae, was apparently small but mighty. Researchers say it had 100 sharp teeth—more than any other known bird in the age of dinosaurs—that ran to the back of the jaw, underneath the eye. The teeth, likely used to chomp insects, "are fused into the skull, which is highly unusual for a dinosaur," researcher Jingmai O'Connor tells Live Science. But that's just one reason she calls this "the weirdest fossil I've ever been lucky enough to study."
The dinosaur also had some rather unique eyes. In most birds, the eye is supported by a ring of basically square bones called scleral ossicles. But this creature's scleral ossicles are spoon-shaped, like those of some modern lizards, and would've formed a cone, like in owls. But whereas an owl's eyes are positioned forward, this dino's eyes faced sideways and "would have bulged out of its head in a manner not seen in any other living animal," per the BBC. All this suggests impeccable vision—at least in daytime. As the opening of the eye was quite small, allowing limited light to enter, vision was likely impaired at night. O'Connor suggests these oddities might be explained through the evolutionary process of miniaturization, which is primarily seen on islands. Per the study published in Nature, the amber is thought to have formed on an ancient island arc. (Scientists recently found the largest known T. rex.)