Researchers have discovered three new species of large, hawk-sized enantiornithine birds from the Late Cretaceous period in Montana, shedding light on the increasing size and ecological diversity of these ancient birds, much like modern raptors.
Discovery of Hawk-Sized Ancient Birds
The three newly identified species, described in a study published in PLOS ONE by Alexander Clark from the University of Chicago and his team, were found in North America. These birds, comparable in size to modern hawks, had strong, raptor-like feet.
Cretaceous Bird Diversity
Enantiornithines, the most diverse group of birds during the Cretaceous, were globally widespread at the time. However, most fossils of these birds come from the Early Cretaceous, with few discoveries from the later stages. This scarcity leaves gaps in understanding bird evolution towards the end of the Mesozoic Era.
New Fossil Evidence in Montana
Clark and his colleagues studied fossils from the Hell Creek Formation in Montana, dating to the Late Cretaceous (68–66 million years ago, just before the mass extinction that wiped out non-avian dinosaurs). The birds were identified by their lower leg bones, with two named as new species, Magnusavis ekalakaensis and Avisaurus darwini, while the third remains an unnamed species of Avisaurus.
Evolutionary Insights
These Late Cretaceous birds were larger than their Early Cretaceous relatives, with Avisaurus darwini weighing over one kilogram—similar to a large hawk. Analysis of their leg bones showed adaptations akin to modern raptors like hawks and owls, with powerful legs and strong feet capable of grasping and carrying prey, indicating their predatory nature.
Significance of the Findings
These discoveries highlight the growing diversity and size of Late Cretaceous birds, illustrating how enantiornithines evolved to fill various ecological roles. The study underscores how even fragmentary fossils can provide valuable insights into ancient bird behavior and evolution.
The authors conclude, "Avisaurids, a group of enantiornithine birds from the latest Cretaceous, demonstrate hindlimb adaptations for strong ankle flexion, suggesting the ability to carry heavy prey, much like modern raptors."
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