Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is a subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya and their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds.
Charadriiformes is a diverse order of small to medium-large birds. It includes about 390 species and has members in all parts of the world. Most charadriiform birds live near water and eat invertebrates or other small animals; however, some are pelagic (seabirds), others frequent deserts, and a few are found in dense forest. Members of this group can also collectively be referred to as shorebirds.
The Apodiformes is an order, or taxonomic grouping, of birds which traditionally contained three living families—the Apodidae (swifts), the Hemiprocnidae (treeswifts), and the Trochilidae (hummingbirds); however, in the Sibley-Ahlquist taxonomy, this order is elevated to the superorder Apodimorphae, in which hummingbirds are separated into a new order, the Trochiliformes. With nearly 450 species identified to date, it is the most diverse order of birds after the Passeriformes.
The Late Cretaceous is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after creta, the Latin word for the white limestone known as chalk. The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period.
The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans, the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over eighty species of Enantiornithes have been named, but some names represent only single bones, so it is likely that not all are valid. The Enantiornithes became extinct at the Cretaceous–Paleogene boundary, along with Hesperornithes and all other non-avian dinosaurs.
Palaeognathae is an infraclass of birds, called paleognaths or palaeognaths, within the class Aves of the clade Archosauria. It is one of the two extant infraclasses of birds, the other being Neognathae, both of which form Neornithes. Palaeognathae contains five extant branches of flightless lineages, termed ratites, and one flying lineage, the Neotropic tinamous. There are 47 species of tinamous, five of kiwis (Apteryx), three of cassowaries (Casuarius), one of emus (Dromaius), two of rheas (Rhea) and two of ostriches (Struthio). Recent research has indicated that paleognaths are monophyletic but the traditional taxonomic split between flightless and flighted forms is incorrect; tinamous are within the ratite radiation, meaning flightlessness arose independently multiple times via parallel evolution.
The evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs named Paraves. Birds are categorized as a biological class, Aves. For more than a century, the small theropod dinosaur Archaeopteryx lithographica from the Late Jurassic period was considered to have been the earliest bird. Modern phylogenies place birds in the dinosaur clade Theropoda. According to the current consensus, Aves and a sister group, the order Crocodilia, together are the sole living members of an unranked reptile clade, the Archosauria. Four distinct lineages of bird survived the Cretaceous–Paleogene extinction event 66 million years ago, giving rise to ostriches and relatives (Palaeognathae), waterfowl (Anseriformes), ground-living fowl (Galliformes), and "modern birds" (Neoaves).
Waimanu is a genus of early penguin which lived during the Paleocene, soon after the Cretaceous–Paleogene extinction event, around 62–60 million years ago. It was about the size of an emperor penguin. It is one of the most important bird fossils for understanding the origin and evolution of birds because of the time period it comes from, and the position of penguins near the base of the bird family tree.
Ichthyornithes is an extinct group of toothed avialan dinosaurs very closely related to the common ancestor of all modern birds. They are known from fossil remains found throughout the late Cretaceous period of North America, though only two genera, Ichthyornis and Janavis, are represented by complete enough fossils to have been named. Ichthyornitheans became extinct at the Cretaceous–Paleogene boundary, along with enantiornitheans, all other non-avian dinosaurs, and many other animal and plant groups.
The Pelagornithidae, commonly called pelagornithids, pseudodontorns, bony-toothed birds, false-toothed birds or pseudotooth birds, are a prehistoric family of large seabirds. Their fossil remains have been found all over the world in rocks dating between the Early Paleocene and the Pliocene-Pleistocene boundary.
Neoaves is a clade that consists of all modern birds with the exception of Palaeognathae and Galloanserae. This group is defined in the PhyloCode by George Sangster and colleagues in 2022 as "the most inclusive crown clade containing Passer domesticus, but not Gallus gallus". Almost 95% of the roughly 10,000 known species of extant birds belong to the Neoaves.
Lithornis is a genus of extinct paleognathous birds. Although Lithornis was able to fly well, their closest relatives are the extant tinamous and ratites.
Pangalliformes is the scientific name of a provisional clade of birds within the group Galloanserae. It is defined as all birds more closely related to chickens than to ducks, and includes all modern chickens, turkeys, pheasants, and megapodes, as well as extinct species that do not fall within the crown group Galliformes.
Australornis is a genus of extinct seabird discovered in New Zealand. It lived in the Paleocene epoch, 60.5 to 61.6 million years ago (Ma). The type species name originates from australis, Latin for "southern", and ornis, the Greek word for "bird", and lovei commemorates Leigh Love, an amateur paleontologist who discovered it.
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the K–T extinction, was the mass extinction of three-quarters of the plant and animal species on Earth approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs. Most other tetrapods weighing more than 25 kg (55 lb) also became extinct, with the exception of some ectothermic species such as sea turtles and crocodilians. It marked the end of the Cretaceous period, and with it the Mesozoic era, while heralding the beginning of the current era, the Cenozoic. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, Fatkito boundary or K–T boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium, which is more common in asteroids than in the Earth's crust.
Vegaviidae is an extinct family of birds of uncertain phylogenetic placement, which existed during the Late Cretaceous and possibly the Paleocene. Definitive fossils attributed to the family have only been found in Antarctica, though other fossils from the Southern Hemisphere including Chile and New Zealand may represent this group. The putative Campanian vegaviid from Canada known as Maaqwi, more likely belongs to the Procellariformes.
Maaqwi is an extinct genus of large marine diving bird from the Late Cretaceous of Hornby Island, British Columbia, Canada. The genus name Maaqwi comes from the Coast Salish "ma'aqwi" meaning "water bird," and the specific epithet cascadensis reflects the fossil's origin from the Cascadia region of Western North America. The genus is known from a single specimen, RBCM.EH2008.011.01120. It consists of a coracoid, humerus, ulna, and radius in a nodule of mudstone. The specimen is housed in the Royal British Columbia Museum. Maaqwi had an estimated body mass of 1.5 kg (3.3 lb). It was described as a vegaviid, although the German paleontologist Gerald Mayr suggested that the coracoid more closely resembles that of the Procellariiformes. While some studies continue to treat it as a vegaviid, others note that the phylogenetic analyses by McLachlan, Kaiser and Longrich (2017) are more appropriate to analyze stem birds than neornithines.
The biogeography of Paravian dinosaurs is the study of the global distribution of Paraves through geological history. Paraves is a clade that includes all of the Theropoda that are more closely related to birds than to oviraptorosaurs. These include Dromaeosauridae and Troodontidae and Avialae. The distribution of paraves is closely related to the evolution of the clade. Understanding the changes in their distributions may shed light on problems like how and why paraves evolve, eventually gaining the ability to fly.
Asteriornis is an extinct genus of bird from the Late Cretaceous of Belgium which is known from a single species, Asteriornis maastrichtensis. It was closely related to birds of the extant superorder Galloanserae such as chickens and ducks. Members of the genus were small, long-legged birds that lived near the coastline and co-existed with more "primitive" types of birds such as Ichthyornis. Asteriornis is one of the oldest-known birds irrefutably belonging to the group Neornithes, which encompasses all modern birds. It possesses characteristics of both galliformes and anseriformes, indicating its position as a close relative of the last common ancestor for both groups.
Kupoupou is an extinct genus of bird from the Paleocene-aged Takatika Grit of the Chatham Islands, New Zealand which is believed to be the oldest penguin genus known to date. The type species, K. stilwelli, was named and described by Blokland et al. in 2019.
