Paleontologists have identified new species of predatory birds that existed on Earth 68 million years ago.

66-68 million years ago, on the island continent of Laramidia, located where the western part of North America is now (the Hell Creek geological formation), ancient predatory birds lived alongside dinosaurs such as Triceratops (Triceratops horridus) and Tyrannosaurus rex (Tyrannosaurus rex). This region is one of the primary sources of information about the ecosystems of Earth during the Late Cretaceous period—here, remains of ancient fish, amphibians, and mammals, as well as many dinosaur species, including Pachycephalosaurus (Pachycephalosaurus wyomingensis), have been discovered.

In a study published in the journal Plos One, paleontologists described three species of extinct birds, two of which belong to the family Avisauridae (part of the larger clade Enantiornithes). At least one of them was a predator and was comparable in size to modern hawks.

Previously, representatives of this family were primarily known from isolated elements of hind limbs found in North and South America. Most of the knowledge about Enantiornithes has been based on fossils from Lower Cretaceous deposits in China. Late Cretaceous finds, in general, have been rare.

A research team led by Alexander D. Clark from the University of Chicago analyzed fossil remains of three tarsometatarsi—one of the leg bones of birds, located between the tibia and the toes—that were found alone, without other body parts such as skulls and claws.

By comparing these remains with the bones of various modern birds, paleontologists concluded that the muscles and the tarsometatarsus of the extinct species functioned like a lever, allowing the birds to grasp and carry prey, similar to how modern owls or hawks do. It is suggested that their prey could have included small mammals as well as dinosaur hatchlings.

Thus, paleontologists described two new species for science: Avisaurus darwini (in honor of Charles Darwin) and Magnusavis ekalakaenis (named after the town of Ekalaka, Montana, where the fossil was found). It was not possible to definitively determine which species the third bone might belong to. This discovery significantly expands the known diversity of birds in the Late Cretaceous period and allows for the study of this group on the eve of the mass extinction.

The results of the study also provide new data on the ecology of the Hell Creek formation. The fact that the discovered fossils belong to ancient predatory birds will allow scientists to better understand the evolution of feathered creatures and their adaptations to various ecological niches.