page_title: Confuciusornis
section_title: Paleoenvironment
hierarchical_section_title: Confuciusornis / Paleoenvironment
caption_attribution_description: English: Sinocalliopteryx gigas as a stealth hunter feeding on the primitive bird Confuciusornis. Illustration by Cheung Chungtat. doi:10.1371/journal.pone.0044012.g008
context_page_description: Confuciusornis is a genus of primitive crow-sized avialan from the Early Cretaceous Period of the Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago. Like modern birds, Confuciusornis had a toothless beak, but close relatives of modern birds such as Hesperornis and Ichthyornis were toothed, indicating that the loss of teeth occurred convergently in Confuciusornis and living birds. It is the oldest known bird to have a beak. It was named after the Chinese moral philosopher Confucius. Confuciusornis is one of the most abundant vertebrates found in the Yixian Formation, and several hundred complete, articulated specimens have been found.
context_section_description: Confuciusornis was discovered in the Yixian and Jiufotang Formations and is a member of the Jehol Biota. Tuff makes up a considerable amount of the rock composition in both due to frequent volcanic eruptions, which were slightly more frequent in the Yixian Formation. Shale and mudstone also are major components of the formations. The tuff has allowed detailed dating of the formations by using ⁴⁰Ar-³⁹Ar isotopes. This results in an age of approximately 125 to 120 million years ago for the Yixian formation and approximately 120.3 million years ago for the Jiufotang Formation. The fossils were buried as a result of flooding and volcanic debris. This method of preservation resulted in fossils that are very flat, almost two-dimensional. The volcanic strata have allowed the preservation of various soft tissues, such as detailed feather impressions. Using oxygen isotopes in reptile bones found in the formation, a 2010 study determined that many formations from East Asia, including the Yixian, had a cool temperate climate. The mean air temperature of the Yixian Formation was estimated at 10 °C ± 4 °C. Fossils of Xenoxylon, a type of wood known from temperate areas of the time, have been found throughout the region. Additionally, reptiles needing heat, such as crocodilians, are absent.
  The majority of Jehol flora has been discovered in the lower Yixian Formation. This flora includes most groups of Mesozoic plants, including mosses, clubmosses, horsetails, ferns, seed ferns, Czekanowskiales, ginkgo trees, cycadeoids, Gnetales, conifers, and a small number of flowering plants. Fauna that were present in the Jehol Biota include ostracods, gastropods, bivalves, insects, fish, salamanders, mammals, lizards, choristoderes, pterosaurs, and dinosaurs (including birds). These dinosaur fossils are exceptionally well preserved, frequently preserving feather impressions and sometimes even pigmentation, such as in Microraptor (an aerial predator), Psittacosaurus (a small ceratopsian), and Sinosauropteryx (a compsognathid). Other feathered dinosaurs of the Jehol Biota include the large compsognathid Sinocalliopteryx gigas, a specimen of which was discovered with Confuciusornis bones in its abdominal contents, the small herbivorous oviraptorosaur Caudipteryx, and the large tyrannosauroid Yutyrannus. Jehol birds are represented by more than 20 genera, including basal birds (such as Confucisornis, Jeholornis, and Sapeornis), enantiornithes (such as Eoenantiornis, Longirostravis, Sinornis, Boluochia, and Longipteryx), and ornithurines (such as Liaoningornis, Yixianornis, and Yanornis).
caption: Sinocalliopteryx preying on Confuciusornis, as indicated by stomach contents of the former
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