Theropoda, whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores and omnivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included the majority of large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species.
Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil discoveries of complete and articulated specimens, have helped to increase understanding about this group. Anatomical studies, particularly studies of the most primitive troodontids, like Sinovenator, demonstrate striking anatomical similarities with Archaeopteryx and primitive dromaeosaurids, and demonstrate that they are relatives comprising a clade called Paraves.
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.
Rapetosaurus is a genus of titanosaurian sauropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period. Only one species, Rapetosaurus krausei, has been identified.
Rahonavis is a genus of bird-like theropods from the Late Cretaceous of what is now northwestern Madagascar. It is known from a partial skeleton found by Catherine Forster and colleagues in Maevarano Formation rocks at a quarry near Berivotra, Mahajanga Province. Rahonavis was a small predator, at about 70 centimetres (2.3 ft) long and 0.45-2.27 kg, with the typical dromaesaurid-like raised sickle claw on the second toe. It was originally the first African coelurosaur until the discovery of Nqwebasaurus in 2000.
Majungasaurus is a genus of abelisaurid theropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period, making it one of the last-known non-avian dinosaurs that went extinct during the Cretaceous–Paleogene extinction event. The genus contains a single species, Majungasaurus crenatissimus. This dinosaur is also called Majungatholus, a name which is considered a junior synonym of Majungasaurus.
Archaeopterygidae is a group of paravian dinosaurs, known from the latest Jurassic and earliest Cretaceous of Europe. In most current classifications, it contains only the genera Archaeopteryx and Wellnhoferia. As its name suggests, Protarchaeopteryx was also once referred to this group, but most paleontologists now consider it an oviraptorosaur. Other referred genera, like Jurapteryx, Wellnhoferia, and "Proornis", are probably synonymous with Archaeopteryx or do not belong into this group. Jinfengopteryx was originally described as an archaeopterygid, though it was later shown to be a troodontid. A few studies have recovered Anchiornis and Xiaotingia to also be members of the Archaeopterygidae, though most subsequent analyses have failed to arrive at the same result. Uncertainties still exist, however, and it may not be possible to confidently state whether archaeopterygids are more closely related to modern birds or to deinonychosaurs barring new and better specimens of relevant species. Teeth attributable to archaeopterygids are known from the earliest Cretaceous (Berriasian) Cherves-de-Cognac locality and the Angeac-Charente bonebed of France.
Ichthyornithes is an extinct group of toothed avialans 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.
Nanantius is a genus of extinct enantiornithean avialan known from the Early Cretaceous of Australia.
The scientific question of within which larger group of animals birds evolved has traditionally been called the "origin of birds". The present scientific consensus is that birds are a group of maniraptoran theropod dinosaurs that originated during the Mesozoic Era.
Compsognathidae is a family of coelurosaurian theropod dinosaurs. Compsognathids were small carnivores, generally conservative in form, hailing from the Jurassic and Cretaceous Periods. The bird-like features of these species, along with other dinosaurs such as Archaeopteryx inspired the idea for the connection between dinosaur reptiles and modern-day avian species. Compsognathid fossils preserve diverse integument — skin impressions are known from four genera commonly placed in the group, Compsognathus, Sinosauropteryx, Sinocalliopteryx, and Juravenator. While the latter three show evidence of a covering of some of the earliest primitive feathers over much of the body, Juravenator and Compsognathus also show evidence of scales on the tail or hind legs. "Ubirajara jubatus", informally described in 2020, had elaborate integumentary structures on its back and shoulders superficially similar to the display feathers of a standardwing bird-of-paradise, and unlike any other non-avian dinosaur currently described.
The Maevarano Formation is a Late Cretaceous sedimentary rock formation found in the Mahajanga Province of northwestern Madagascar. It is most likely Maastrichtian in age, and records a seasonal, semiarid environment with rivers that had greatly varying discharges. Notable animal fossils recovered include the theropod dinosaur Majungasaurus, the early bird Vorona, the paravian Rahonavis, the titanosaurian sauropod Rapetosaurus, and the giant frog Beelzebufo.
Neuquenornis volans is a species of enantiornithean birds which lived during the late Cretaceous period in today's Patagonia, Argentina. It is the only known species of the genus Neuquenornis. Its fossils were found in the Santonian Bajo de la Carpa Formation, dating from about 85-83 million years ago. This was a sizeable bird for its time, with a tarsometatarsus 46.8mm long. Informal estimates suggest that it measured nearly 30 cm (12 in) in length excluding the tail.
Euornithes is a natural group which includes the most recent common ancestor of all avialans closer to modern birds than to Sinornis.
Hollanda is a genus of small ground birds known from fossils found in the Barun Goyot Formation of Mongolia. Found at Khermeen Tsav, it dates from the late Cretaceous period, about 75 million years ago. Known only from partial hind limbs, Hollanda has long legs with an unusual configuration of the toes. These indicate that it was a fast-running ground bird, possibly similar to the modern Roadrunner. Its relationships are uncertain. Some studies have found that it was an relatively advanced bird, a member of the Ornithurae, related to birds like Ichthyornis. Other studies have recovered it as a member of the primitive family Songlingornithidae. A more expansive study found it as an enantiornithean. Dinosaur Institute at the Natural History Museum of Los Angeles County project lead and researcher, Alyssa Bell, named the new species after the Holland family and the rock band Lucero.
Evgenavis is a genus of extinct basal bird that lived from the Barremian to the Aptian. The type specimen ZIN PH 1/154 is an isolated tarsometatarsus found in the Ilek Formation, Western Siberia. Evgenavis may have been the only confuciusornithiform known outside the Jehol Biota, although there is also the possibility that it could have been a different type of avialan, such as an enantiornithean or a relative of Vorona. A cladogram within a 2019 study involving a wide range of theropods included Evgenavis as a longipterygid.
The year 2018 in archosaur paleontology was eventful. Archosaurs include the only living dinosaur group — birds — and the reptile crocodilians, plus all extinct dinosaurs, extinct crocodilian relatives, and pterosaurs. Archosaur palaeontology is the scientific study of those animals, especially as they existed before the Holocene Epoch began about 11,700 years ago. The year 2018 in paleontology included various significant developments regarding archosaurs.
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.
