Neornithes refers to the modern group of birds that are characterized by their unique features, such as a beak without teeth, lightweight skeletons, and feathers. This group includes all living bird species, which are divided into two main lineages: Palaeognathae, which includes flightless birds like ostriches and kiwis, and Neognathae, which encompasses the majority of bird species that can fly. Neornithes are believed to have evolved from earlier avian ancestors during the Cretaceous period, around 100 million years ago. They play crucial roles in ecosystems as pollinators, seed dispersers, and predators, contributing to biodiversity and ecological balance across various habitats worldwide.