Maastrichtian in the context of "Sturgeon"

Maastricht (/ˈmɑːstrɪxt/ MAH-strikht, US also /mɑːˈstrɪxt/ mah-STRIKHT, Dutch: [maːˈstrɪxt] ; Limburgish: Mestreech [məˈstʀeːx]) is a city and a municipality in the southeastern Netherlands. It is the capital and largest city of the province of Limburg. Maastricht is located on both sides of the Meuse (Dutch: Maas), at the point where the river is joined by the Jeker. Mount Saint Peter (Sint-Pietersberg) is largely situated within the city's municipal borders. Maastricht is adjacent to the border with Belgium and is part of the Meuse-Rhine Euroregion, an international metropolis with a population of about 3.9 million, which includes the nearby German and Belgian cities of Aachen, Liège, and Hasselt.

Maastricht developed from a Roman settlement (Trajectum ad Mosam) to a medieval river trade and religious centre. In the 16th century it became a garrison town and in the 19th century an early industrial centre. Today, the city is a thriving cultural and regional hub. It became well known through the Maastricht Treaty and as the birthplace of the euro. Maastricht has 1,677 national heritage buildings (rijksmonumenten), the second highest number in the Netherlands, after Amsterdam. The city is visited by tourists for shopping and recreation, and has a large international student population. The last stage of the Cretaceous period and the Mesozoic era, the Maastrichtian, is named after this city, at the end of which was the Cretaceous–Paleogene extinction event, which resulted in the extinction of the non-avian dinosaurs.

A bird colony is a large congregation of individuals of one or more species of bird that nest or roost in proximity at a particular location. Many kinds of birds are known to congregate in groups of varying size; a congregation of nesting birds is called a breeding colony. Colonial nesting birds include seabirds such as auks and albatrosses; wetland species such as herons; and a few passerines such as weaverbirds, certain blackbirds, and some swallows. A group of birds congregating for rest is called a communal roost. Evidence of colonial nesting has been found in non-neornithine birds (Enantiornithes), in sediments from the Late Cretaceous (Maastrichtian) of Romania.

Tyrannosaurus (/tɪˌrænəˈsɔːrəs, taɪ-/) is a genus of large theropod dinosaur. The type species Tyrannosaurus rex (rex meaning 'king' in Latin), often shortened to T. rex or colloquially t-rex, is one of the best represented theropods. It lived throughout what is now western North America, on what was then an island continent known as Laramidia. Tyrannosaurus had a much wider range than other tyrannosaurids. Fossils are found in a variety of geological formations dating to the late Maastrichtian age of the late Cretaceous period, 69 to 66 million years ago, with isolated specimens possibly indicating an earlier origin in the middle Campanian age. It was one of the last known members of the tyrannosaurids and among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event.

Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to its large and powerful hind limbs, the forelimbs of Tyrannosaurus were short but unusually powerful for their size, and they had two clawed digits. The most complete specimen measures 12.3–12.4 m (40–41 ft) in length, but according to most modern estimates, Tyrannosaurus could have exceeded sizes of 13 m (43 ft) in length, 3.7–4 m (12–13 ft) in hip height, and 8.8 t (8.7 long tons; 9.7 short tons) in mass. Although some other theropods might have rivaled or exceeded Tyrannosaurus in size, it is still among the largest known land predators, with its estimated bite force being the largest among all terrestrial animals. By far the largest carnivore in its environment, Tyrannosaurus rex was most likely an apex predator, preying upon hadrosaurs, juvenile armored herbivores like ceratopsians and ankylosaurs, and possibly sauropods. Some experts have suggested the dinosaur was primarily a scavenger. The question of whether Tyrannosaurus was an apex predator or a pure scavenger was among the longest debates in paleontology. Most paleontologists today accept that Tyrannosaurus was both a predator and a scavenger.

Insular India was an isolated landmass which became the Indian subcontinent. Across the latter stages of the Cretaceous and most of the Paleocene, following the breakup of Gondwana, the Indian subcontinent remained an isolated landmass as the Indian Plate drifted across the Tethys Ocean, forming the Indian Ocean. The process of India's separation from Madagascar first began 88 million years ago, but complete isolation only occurred towards the end of the Maastrichtian, a process that has been suggested to be the creation of the Deccan Traps. Soon after, the land mass moved northward rather quickly, until contact with Asia was established 55 million years ago. Even then, both landmasses did not become fully united until around 35 million years ago, and periods of isolation occurred as recently as 24 million years ago.

Thus, for a period of 53 million years India retained a degree of isolation, 11 of which it was a complete island continent. This allowed its local biota to follow the typical patterns seen in islands and diversify in unique ways, much as in modern Madagascar, its sister landmass. Faunal interchanges with other landmasses, like Africa and Europe (then an archipelago of islands across the Tethys) occurred during this period, and a considerable Asian influence can already be seen long before contact was made. This rendered India rather peculiar as not just an isolated continent but also a "stepping stone" in the dispersal of many animal and plant clades across Africa, Europe, Madagascar, Asia and possibly even Oceania. Still, several "archaic" clades managed to survive. The vast majority of India's terrestrial vertebrate life was wiped out in the Cretaceous-Paleogene extinction event; only 3 extant tetrapod lineages can trace their ancestry to Cretaceous India. Most of India's few other surviving Gondwanan lineages were outcompeted during the Paleogene by newly-arriving lineages. However, plants and invertebrate fauna were less affected.

Neognathae (/niˈɒɡnəθiː/; from Ancient Greek νέος (néos) 'new, young' and γνάθος (gnáthos) 'jaw') is an infraclass of birds, called neognaths, within the class Aves of the clade Archosauria. Neognathae includes the majority of living birds; the exceptions being the tinamous and the flightless ratites, which belong instead to the sister taxon Palaeognathae. There are nearly 10,000 living species of neognaths.

The earliest fossils are known from the very end of the Cretaceous period, specifically during the Maastrichtian stage. As of 2025, the neognath genera from the latest Cretaceous supported by phylogenetic analyses include Asteriornis, Vegavis, Polarornis and Pujatopouli, but molecular clocks suggest that neognaths originated sometime in the first half of the Late Cretaceous, about 90 million years ago. Since then, they have undergone adaptive radiation, producing the diversity of form, function, and behavior that exists today. Neognathae includes the order Passeriformes (perching birds), one of the largest orders of land vertebrates, containing some 60% of living birds. Passeriformes is twice as species-rich as Rodentia and about five times as species-rich as Chiroptera (bats), which are the two largest orders of mammals. Neognathae also contains some very small orders, often birds of unclear relationships like the hoatzin.

The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian spans the time from 83.6 (± 0.2) to 72.2 (± 0.2) million years ago. It is preceded by the Santonian and it is followed by the Maastrichtian.

The Campanian was an age when a worldwide sea level rise covered many coastal areas. The morphology of some of these areas has been preserved: it is an unconformity beneath a cover of marine sedimentary rocks.

Dromaeosauridae (/ˌdrɒmi.əˈsɔːrɪdiː/) is a family of feathered coelurosaurian theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek δρομαῖος (dromaîos), meaning 'running at full speed', 'swift', and σαῦρος (saûros), meaning 'lizard'. In informal usage, they are often called raptors (after Velociraptor), a term popularized by the film Jurassic Park; several genera include the term "raptor" directly in their name, and popular culture has come to emphasize their bird-like appearance and speculated bird-like behavior.

Definitive dromaeosaurid fossils have been found in North America, Europe and Asia. Some paravian fossils found in other continents have been traditionally regarded as dromaeosaurids, but have recently been reinterpreted as a unique family Unenlagiidae outside Dromaeosauridae, with some authors considering them as a separate lineage of Avialae. The earliest body fossils are known from the Early Cretaceous (145–140 million years ago), and they survived until the end of the Cretaceous (Maastrichtian stage, 66 ma), existing until the Cretaceous–Paleogene extinction event. The presence of dromaeosaurids as early as the Middle Jurassic has been suggested by the discovery of isolated fossil teeth, though no dromaeosaurid body fossils have been found from this period.

Hesperornis (from Ancient Greek ἕσπερος (hésperos), meaning "western", and ὄρνις (órnis), meaning "bird") is a genus of cormorant-like ornithuran that spanned throughout the Campanian age, and possibly even up to the early Maastrichtian age, of the Late Cretaceous period. One of the lesser-known discoveries of the paleontologist O. C. Marsh in the late 19th century Bone Wars, it was an early find in the history of avian paleontology. Locations for Hesperornis fossils include the Late Cretaceous marine limestones from Kansas and the marine shales from Canada. Nine species are recognised, eight of which have been recovered from rocks in North America and one from Russia.