Ancient bird skull found in amber was tiny predator in the time of giant dinosaurs

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

Paleontologists are far from having a complete picture of evolution of birds, and even farr from a full inventory of Earth’s ecosystems in of disaurs. Our research on tiny Oculudentavis, published in journal Nature, ds valuable information to puzzle of when, how and to what extent disaurs shrank.

Our team needed to see minute details of skull, and we needed to do it without cracking or ruining specimen - a difficult task with a skull encased in 99-million-year old amber from Myanmar. To do that, we scanned 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 disaur that has ever been found.

obvious curiosity of fossil is its size: Oculudentavis rivaled smallest bird living today, bee hummingbird, and likely was more than 1.6 inches (4 centimeters) from beak to tail. We considered wher skull possibly belonged to a very young animal, but extent and pattern of bone growth and proportional size of 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 lower limit of size in birds: he still h to hold functional eyes, a brain and jaws. small size is especially surprising if one considers that Oculudentavis lived during same time as

small size of Oculudentavis is striking, but to a trained eye re are or extremely unusual features, too.

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

eyes of Oculudentavis also surprised us. shape of bones found within eye, scleral ossicles, suggests that it probably h conical eyes with small pupils. This of eye structure is especially well apted for moving around in bright light. While daytime activity might be expected for an

ding to list of unexpected features, upper jaw carries at least 23 small teeth. se teeth extend all way back beneath eye and are t set in deep pockets, an unusual arrangement for most ancient birds. large number of teeth and ir sharp cutting edges suggest that Oculudentavis was a predator that may have fed on small bugs.

sum of se traits – a strong skull, good eyesight and a hunter’s set of teeth – suggests to us that Oculudentavis led a life previously unkwn among ancient birds: it was a hummingbird-sized daytime predator.

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

Scientists consider nectar-feeding hummingbirds –

Our work demonstrates how little scientists kw about little things in history of life. Scientists’ snapshot of fossil ecosystems in disaur is incomplete and leaves so many questions unanswered. But paleontologists are er to take on se questions. What or tiny species were out re? What was ir ecological function? Was Oculudentavis only visually guided bug hunter? To better understand evolution of diversity of life we need more emphasis and recognition of small.

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