A bird’s skull from Myanmar reveals a missing ecosystem with small fossils ready to be discovered.
The term “dinosaurs” conjures up visions of horrific and massive reptiles. Yet not all the “terrible lizards” had been massive. Much of their popularity was attributed to their having come in various shapes and sizes. And paleontologists have now discovered what might be the tiniest dinosaur yet.
Described in a report reported Wednesday in Nature by the China University of Geosciences paleontologist Lida Xing and his colleagues, the 99-million-year-old fossil was discovered in Myanmar and is one of a increasing range of amber-bound windows into the Mesozoic Era.
In recent years, palaeontologists have found fossil tongues, baby chicks, different types of insects and even seagoing animals that have been trapped in sticky sap gobs. Nonetheless, what makes this new discovery stand out is just how small it is.
The recently found fossil, preserved during the Mid-Cretaceous Era of the Mesozoic Age in hardened resin, is depicted by little more than a skeleton.
It is just about half an inch long, from its tiny teeth to the fragile ringed bones of its head.
Yet even though amber-encased fossils are often challenging to study — because archaeologists have to focus on photographic tools to break through the resin layers — it’s clear that this little guy was a dented bird that existed under the reign of its dinosaur relatives. It was called Oculudentavis khaungrae by Xing and his co-authors — with the genus originating from the Latin “toothed eye owl” and the species assigned in memory of the fossil collector Khaung Ra, who donated the object for research.
It’s not even obvious precisely where Oculudentavis sits on the bird family tree.
It appears to be a relatively archaic form called stem bird by paleontologists — a bird close to the point where avians split from their feathered dinosaur ancestors. Then again, more analyzes or fossil discoveries may alter the branch on which it is put. While Oculudentavis still seems to be a duck, says paleontologist Daniel Ksepka, “I would not be surprised if it turned out to fall somewhere else in the bird part of the dinosaur family tree.”
The tiny animal ‘s eyes were what most excited co-author of the study Lars Schmitz, a paleontologist at Claremont McKenna, Scripps and Pitzer colleges. “I must say the scleral ring of Oculudentavis is just great,” says Schmitz, adding that each eye’s small, fragile bones are in position and just somewhat deformed by fossilization. These bones may be organized to tell something about when Oculudentavis was healthy. “The individual bones of the ring have an odd lizard-like shape. And the proportional size of the opening where the pupil would have been suggests daytime activity,” says Schmitz.
Oculudentavis in fact must have been around the height of a medium colibris. This size makes it the tiniest ever found Mesozoic dinosaur, far lower than many title candidates including Fruitadens in Colorado. And finding tiny animals has a major impact on how the history is interpreted by paleontologists. Huge dinosaurs were among the first to be identified and to achieve prominence. Not only did these organisms have robust bones capable of resisting the brutality of deterioration and restoration, but (especially during the early 20th century) museums and paleontologists deliberately looked for huge, intimidating specimens that would help create careers and increase the attendance of the exhibits.
Scientific infatuation with larger dinosaurs was so strong that often “headhunted” became insightful and significant fossils, since finding spectacular skulls was seen as more crucial to constructing collections. Yet the fossil hunters have traditionally overlooked miniature specimens, suggesting that there are probably tiny organisms waiting to be discovered. In addition to finds in other locations — such as the Liaoning Province’s fossil beds in China, which have produced hundreds of excellent specimens — Oculudentavis and new studies of Myanmar’s amber have begun to establish a picture of the dinosaur environment that varies from what has been gathered from classic sites in the American West.
And the current result is important over time with the variety of sizes birds have taken. “I was amazed by how small this fossil was,” says Ksepka. To be sure, a stronger body fossil is required but Oculudentavis may be smaller than even the smallest current birds. If that probability turned out to be the case, Ksepka states, that will imply extinction of the largest and smallest birds of all time. Further discoveries including Oculudentavis are expected to follow. “We are currently only capturing a small fraction of the small end of the size spectrum, with an incomplete picture of the biodiversity in the age of dinosaurs,” says Schmitz.
Also in fairly common fossil-producing areas, comparatively small are the most possible candidates for new life. These animals are just as critical as the hulking bone mountains which fill the halls of museums. They are the threads that helped to shape habitats underneath giants’ feet.