American paleontologists have made a unique discovery – in Burmese amber, famous for its many fossils of Mesozoic age, they found the skull of a tiny bird-like dinosaur, no larger than a hummingbird. Presumably, the skull belonged to an adult. The discovery is described in the journal Nature.
Analyzing samples of Mesozoic amber from Myanmar, associate Professor of Biology Lars Schmitz from Scripps College in California came across an amazing find — a small skull of an unknown vertebrate, similar in shape and size to the skull of the smallest modern bird, the Hummingbird. Finds of vertebrate fossils in amber are rare in themselves, but this case has become unique in all respects. The age of the find is 99 million years.
First, it turned out that the skull belongs to a bird-like dinosaur-the smallest ever found, and, judging by all signs, it is the skull of an adult representative of the species, which scientists have given the name Oculudentavis khaungraae.
Second, this finding forces a completely new look at the evolution of dinosaurs and the origin of birds. It turns out that birds that separated themselves from the dinosaurs very early did not evolve along the path of reducing the size, as previously thought, but in a more complex way.
“The preservation of vertebrates in amber is rare, and this gives us an idea of the smallest representative of the entire line of dinosaurs,” Lars Schmitz said in a press release from the College. — Its unique anatomical features point to one of the smallest and most ancient birds ever found.”
Scientists studied the features of the find using high-resolution synchrotron scanning and determined that the skull of Oculudentavis khaungraae differs from the skulls of other bird-like dinosaurs of the era, showing an unprecedented combination of features. The shape and size of the eye sockets suggest a diurnal lifestyle, but also reveal a surprising resemblance to the eyes of modern lizards. The bones of the skull show a unique example of the fusion of various bone elements, and the beak is combined with strong jaws that had from 29 to 30 teeth. This suggests that, despite its small size, Oculudentavis, whose name is made up of three Latin words “eye-tooth-bird,” was a predator and probably fed on small arthropods or invertebrates, in contrast to modern birds of similar size, which do not have teeth and feed on nectar.
According to the authors, the found sample represents a link that was previously absent in the chronicle of transitional forms between dinosaurs and birds, and gives a new understanding of the evolution of birds, indicating that in its early stages there were extremely small-sized species.
“No other group of modern birds has individuals with the same small skulls in adults,” says Schmitz. — This discovery shows us that we still have a very limited understanding of what small vertebrates looked like in the age of dinosaurs.”
Scientists believe that this finding makes us reconsider the potential of amber deposits in terms of finding parts of the skeleton of small Mesozoic vertebrates in it.