Ornithuromorphs

Ornithuromorpha is a clade of extinct avialan dinosaurs that lived during the Mesozoic Era. This group is considered to be the immediate ancestors of modern birds, making them of significant interest to paleontologists studying avian evolution. Ornithuromorphs are characterized by a combination of avian and non-avian dinosaur traits, representing a transitional stage in the development of birds.

Fossil evidence of ornithuromorphs has been discovered primarily in China, with notable examples including species like *Ichthyornis* and *Hesperornis*. These fossils often preserve detailed anatomical features, providing insights into their skeletal structure, feathering, and even diet. Many ornithuromorphs possessed bird-like features such as a furcula (wishbone), a reversed hallux (the first toe, pointing backward), and a pygostyle (fused tail vertebrae), which are also found in modern birds. However, they retained some reptilian characteristics, such as teeth in their jaws, which are absent in most living birds.

The evolution of ornithuromorpha is a key chapter in understanding how dinosaurs transitioned into birds. Their adaptations, such as the development of flight capabilities in some lineages, paved the way for the diversification of birds into the myriad of species seen today. Studying these ancient relatives helps to clarify the evolutionary pathways and the selective pressures that shaped the lineage leading to modern Aves.