Quantitative investigation of pengornithid enantiornithine diet reveals macrocarnivorous ecology evolved in birds by Early Cretaceous.

The diet of Mesozoic birds is poorly known, limiting evolutionary understanding of birds' roles in modern ecosystems. Pengornithidae is one of the best understood families of Mesozoic birds, hypothesized to eat insects or only small amounts of meat. We investigate these hypotheses with four lines of evidence: estimated body mass, claw traditional morphometrics, jaw mechanical advantage, and jaw finite element analysis. Owing to limited data, the diets of and remain obscure. , , and show adaptations for vertebrate carnivory. also has talons similar to living raptorial birds like caracaras that capture and kill large prey, which represents the earliest known adaptation for macrocarnivory in a bird. This supports the appearance of this ecology ∼35 million years earlier than previously thought. These findings greatly increase the niche breadth known for Early Cretaceous birds, and shift the prevailing view that Mesozoic birds mainly occupied low trophic levels.