Prehistoric Bird Fossil Offers Clues to Evolution

The find of an early bird with a tall, sickle-shaped beak reveals hidden species diversity during the age of dinosaurs, according to an international team of researchers led by Alan H. Turner of Stony Brook University and Patrick O’Connor of Ohio University. The findings are detailed in a paper published in Nature.
The newly discovered, crow-sized bird fossil that would have sliced its way through the air wielding a large, blade-like beak, offers new insight into the evolution of face and beak shape in the Mesozoic forerunners of modern birds.

Falcatakely fossil

Illustration depicting Falcatakely amid nonavian dinosaurs and other creatures during the Late Cretaceous in Madagascar. (Credit: Mark Witton)

Birds have played a pivotal role shaping our understanding of biological evolution. As far back as the mid-19th century, Charles Darwin’s keen observations on the diversity of beak shape in Galapagos finches influenced his treatise on evolution through natural selection. The new fossil bird discovery adds a novel twist on the evolution of skulls and beaks in birds, showing that evolution can work through different developmental pathways to achieve similar head/beak shapes in very distantly related animals.
The new bird is named Falcatakely forsterae, or just Falcatakely, a combination of Latin and Malagasy words inspired by the small size and the sickle-shaped beak, the latter representing a completely novel face shape in Mesozoic birds. The new species is known from a single well-preserved but partial skull. Bird skeletons are rare in the fossil record because of their lightweight bones and small size. Bird skulls are an even rarer find. Nevertheless, Falcatakely is now the second bird discovered from this region of Madagascar by the National Science Foundation (NSF)-funded team.
“We don’t really know why certain beak shapes evolve, but we do know they are used for a multitude of functions such as object manipulation, feather grooming, feeding, and other life-sustaining behaviors,” said Turner, associate professor in the Department of Anatomical Sciences in the Renaissance School of Medicine at Stony Brook University and study co-author.
“In the case of Falcatakely, that was probably the same, and it is significant to discover that this early bird during the Cretaceous had such a uniquely evolved beak.”
Falcatakely belongs to an extinct group of birds called Enantiornithines, a group known exclusively from the Cretaceous Period and predominantly from fossils discovered in Asia.
“Enantiornithines represent the first great diversification of early birds, occupying ecosystems alongside their non-avian relatives such as Velociraptor and Tyrannosaurus,” Turner said. “Unlike the first birds, such as Archaeopteryx, with long tails and primitive features in the skull, enantiornithines like Falcatakely would have looked relatively modern.”
The delicate specimen remains partially embedded in rock due to the complex array of lightly built bones that make up the skull in birds. Although quite small, with an estimated skull length of only 8.5 cm (~ 3 inches), the exquisite quality of preservation is outstanding and reveals many important details. As one example, a complex series of grooves on the external surface of bones making up the side of the face indicate that the animal hosted an expansive keratinous covering, or beak, in life.
Falcatakely bird

Artist reconstruction of the Late Cretaceous enantiornithine bird Falcatakely forsterae with its unique beak. (Credit: Mark Witton)

A life reconstruction of Falcatakely might leave one with the impression that this is a relatively unremarkable bird. But it is underneath the keratinous beak that the evolutionary intrigue lies. But Turner and his colleagues couldn’t remove the individual bones of Falcatakely from the rock to study because they were much too fragile. Instead, the research team employed high-resolution micro-computed tomography (µCT) and extensive digital modeling to virtually dissect individual bones from the rock, with 3D printing of these models being essential for reconstructing the skull and for comparisons with other species. As the research progressed, it was quickly apparent that bones making up the face in Falcatakely are organized quite unlike those of any dinosaur, avian or nonavian, despite having a face superficially similar to a number of modern bird groups alive today.
All living birds build the skeleton of their beaks in a very specific way. It’s mostly formed by a single enlarged bone call the premaxilla. In constrast, most birds from the age of dinosaurs, like the iconic Archaeopteryx, have relatively unspecialized snouts comprised of a small premaxilla and a large maxilla. Surprisingly, in Falcatakely the researchers found this similar primitive arrangement of bones but with an overall face shape reminiscent of certain modern birds with a high, long upper bill and completely unlike anything known in the Mesozoic.
“It turns out you can make a modern looking beak in multiple ways,”  Turner said. “The developmental basis for the skeleton of modern beaks didn’t need to be there for a ‘modern’ looking beak to evolve.”
Falcatakely was recovered from latest Cretaceous-age (70-68 million years ago) rocks in what is now northwestern Madagascar, in what has been interpreted as a rough and tumble environment. That very same environment also hosted a number of other bizarre animals, such as the pug-nosed, herbivorous crocodyliform Simosuchus and the recently described mammal Adalatherium.
“To push the boundaries of our knowledge of Earth history and biological evolution, we have to look in unexplored or underexplored regions,” Turner said. “This discovery highlights the importance of Stony Brook’s long-term research presence in Madagascar and ongoing collaboration with the scientists and citizens of the country.”

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