The Cenozoic is Earth's current geological era, representing the last 66 million years of Earth's history. It is characterized by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configuration of continents. It is the latest of three geological eras since complex life evolved, preceded by the Mesozoic and Paleozoic. It started with the Cretaceous–Paleogene extinction event, when many species, including the non-avian dinosaurs, became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body, the Chicxulub impactor.
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 the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya; 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, or birds; and the extinct non-avian dinosaurs, which are all dinosaurs other than birds.
The Mesozoic Era, also called the Age of Reptiles and the Age of Conifers, is the second-to-last era of Earth's geological history, lasting from about 252 to 66 million years ago and comprising the Triassic, Jurassic and Cretaceous Periods. It is characterized by the dominance of archosaurian reptiles, like the dinosaurs; an abundance of conifers and ferns; a hot greenhouse climate; and the tectonic break-up of Pangaea. The Mesozoic is the middle of three eras since complex life evolved: the Paleozoic, the Mesozoic, and the Cenozoic.
The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years to the present, and it began with the Cambrian Period when animals first developed hard shells preserved in the fossil record. The time before the Phanerozoic, called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons.
Theropoda, whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three-toed limbs. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores, omnivores, piscivores, and insectivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included all the 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.
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 the white limestone known as chalk, which occurs widely in northern France and is seen in the white cliffs of south-eastern England, and which dates from this time.
Pseudoextinction of a species occurs when all members of the species are extinct, but members of a daughter species remain alive. The term pseudoextinction refers to the evolution of a species into a new form, with the resultant disappearance of the ancestral form. Pseudoextinction results in the relationship between ancestor and descendant still existing even though the ancestor species no longer exists.
The New Dinosaurs: An Alternative Evolution is a 1988 speculative evolution book written by Scottish geologist Dougal Dixon and illustrated by several illustrators including Amanda Barlow, Peter Barrett, John Butler, Jeane Colville, Anthony Duke, Andy Farmer, Lee Gibbons, Steve Holden, Philip Hood, Martin Knowelden, Sean Milne, Denys Ovenden and Joyce Tuhill. The book also features a foreword by Desmond Morris. The New Dinosaurs explores a hypothetical alternate Earth, complete with animals and ecosystems, where the Cretaceous-Paleogene extinction event never occurred, leaving non-avian dinosaurs and other Mesozoic animals an additional 65 million years to evolve and adapt over the course of the Cenozoic to the present day.
The Maastrichtian is, in the ICS geologic timescale, the latest age of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from 72.1 to 66 million years ago. The Maastrichtian was preceded by the Campanian and succeeded by the Danian.
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 (Paleognathae), ducks and relatives (Anseriformes), ground-living fowl (Galliformes), and "modern birds" (Neoaves).
Palaeosaniwa canadensis is an extinct species of carnivorous lizard from the late Cretaceous of North America. The name, given by Charles Whitney Gilmore in 1928, means "ancient Saniwa from Canada".
Cimolopteryx is a prehistoric bird genus from the Late Cretaceous Period. It is currently thought to contain only a single species, Cimolopteryx rara. The only specimen confidently attributed to C. rara was found in the Lance Formation of Wyoming, dating to the end of the Maastrichtian age, which ended about 66 million years ago. The dubious species "Cimolopteryx" maxima has been described from both the Lance Formation and the Hell Creek Formation of Montana. The humeral end of a left coracoid from the Frenchman Formation of southern Saskatchewan has also been attributed to the genus.
Albertonykus is an alvarezsaurid dinosaur from the Maastrichtian-age rocks of the Horseshoe Canyon Formation of Alberta, Canada. It is known from forelimb and hindlimb remains from multiple individuals. All but two of the specimens come from a bonebed dominated by Albertosaurus, located at the top of Unit 4 of the Horseshoe Canyon Formation, dating to ~68.5 million years ago.
Austroraptor is a genus of dromaeosaurid theropod dinosaur that lived during the Late Cretaceous Period in what is now Argentina. Austroraptor was a medium-sized, moderately-built, ground-dwelling, bipedal carnivore. It is one of the largest dromaeosaurids known, with only Achillobator, Dakotaraptor, and Utahraptor approaching or surpassing it in length.
The Jurassic Museum of Asturias is located in the area of Rasa de San Telmo near the parish of Llastres in the municipality of Colunga, Asturias, Spain. Though the municipality of Ribadesella was initially proposed, Colunga was chosen for the building site in the late 1990s. Several landmarks are visible from the museum including the Bay of Biscay, the Sierra del Sueve, and the Picos de Europa. Strategically located over a mount on the Rasa de San Temo, the museum is in the midst the Jurassic Asturias.
The climate across the Cretaceous–Paleogene boundary is very important to geologic time as it marks a catastrophic global extinction event. Numerous theories have been proposed as to why this extinction event happened including an asteroid known as the Chicxulub asteroid, volcanism, or sea level changes. While the mass extinction is well documented, there is much debate about the immediate and long-term climatic and environmental changes caused by the event. The terrestrial climates at this time are poorly known, which limits the understanding of environmentally driven changes in biodiversity that occurred before the Chicxulub crater impact. Oxygen isotopes across the K–T boundary suggest that oceanic temperatures fluctuated in the Late Cretaceous and through the boundary itself. Carbon isotope measurements of benthic foraminifera at the K–T boundary suggest rapid, repeated fluctuations in oceanic productivity in the 3 million years before the final extinction, and that productivity and ocean circulation ended abruptly for at least tens of thousands of years just after the boundary, indicating devastation of terrestrial and marine ecosystems. Some researchers suggest that climate change is the main connection between the impact and the extinction. The impact perturbed the climate system with long-term effects that were much worse than the immediate, direct consequences of the impact.
Changyuraptor is a genus of "four-winged", predatory dinosaurs. It is known from a single fossil specimen representing the species Changyuraptor yangi, which was discovered from Early Cretaceous deposits in Liaoning Province, China. C. yangi belongs to the group of dromaeosaurid theropod dinosaurs called the Microraptoria.
The Cretaceous–Paleogene (K–Pg) extinction event was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the exception of some ectothermic species such as sea turtles and crocodilians, no tetrapods weighing more than 25 kilograms survived. It marked the end of the Cretaceous Period, and with it the Mesozoic era, while heralding the beginning of the Cenozoic era, which continues to this day.
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.
