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 Lance (Creek) Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas. The Lance Formation is Late Maastrichtian in age, and shares much fauna with the Hell Creek Formation of Montana and North Dakota, the Frenchman Formation of southwest Saskatchewan, and the lower part of the Scollard Formation of Alberta.
Sphaerotholus is a genus of pachycephalosaurid dinosaur from the Upper Cretaceous of the western United States and Canada. To date, five species have been described: the type species, S. goodwini, from the Den-na-zin Member of the Kirtland Formation of San Juan County, New Mexico, USA; S. buchholtzae, from the Hell Creek Formation of western Carter County, Montana, USA and the Frenchman Formation of Saskatchewan, Canada; S. edmontonensis, from the Horseshoe Canyon Formation of Alberta, Canada; S. lyonsi, from the Dinosaur Park Formation (Campanian) of Alberta, Canada; and S. triregnum from the Hell Creek Formation of Garfield County, Montana, USA.
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.
The Frenchman Formation is stratigraphic unit of Late Cretaceous age in the Western Canada Sedimentary Basin. It is present in southern Saskatchewan and the Cypress Hills of southeastern Alberta. The formation was defined by G.M. Furnival in 1942 from observations of outcrops along the Frenchman River, between Ravenscrag and Highway 37. It contains the youngest of dinosaur genera, much like the Hell Creek Formation in the United States.
Sinornis is a genus of enantiornithean birds from the Lower Cretaceous Jiufotang Formation of the People's Republic of China.
Ceramornis is a prehistoric bird genus from the Late Cretaceous. It lived shortly before the Cretaceous–Paleogene extinction event in the Maastrichtian, some 66 million years ago (mya). Its remains were found in the Lull 2 location, a Lance Formation site in Niobrara County, Wyoming. A single species is known, Ceramornis major, and even that only from a proximal piece of coracoid. This is specimen UCMP V53957, which was collected by a University of California team in 1958.
Palintropus is a prehistoric bird genus from the Late Cretaceous. A single species has been named based on a proximal coracoid from the Lance Formation of Wyoming, dated to the latest Maastrichtian, 66 million years ago. Coracoids and a proximal scapula of two unnamed species from the upper Campanian Dinosaur Park Formation of Alberta, dating to between 76.5 and 75 million years ago, are also known.
Telmatornis is a valid prehistoric bird genus which has been placed in Charadriiformes. It apparently lived in the Late Cretaceous; its remains were found in the early Maastrichtian Navesink Formation of New Jersey. A single species is included today, Telmatornis priscus.
Palaeotringa is a prehistoric bird genus that was discovered by O. C. Marsh during the late 19th century American bone wars. Its remains were found in the controversial Hornerstown Formation of New Jersey which straddles the Cretaceous-Paleocene boundary some 66 million years ago. Though it cannot be said if these birds lived before or after the Cretaceous–Paleogene extinction event, they were in all likelihood wading birds that inhabited the coasts of the northwestern Atlantic.
Qinornis is a prehistoric bird genus from the early-mid-Paleocene epoch, about 61 million years ago. It is known from a single fossil specimen consisting of a partial hind limb and foot, which was found in Fangou Formation deposits in Luonan County, China.
Cimolopterygidae is an extinct family of ornithurines known from the Late Cretaceous epoch. Remains attributed to cimolopterygids have been found in the Frenchman Formation of Saskatchewan, the Lance Formation of Wyoming, the Fox Hills Formation of Colorado, the Hell Creek Formation of Montana, and the Allen Formation of Rio Negro, Argentina. Most date to the end of the Maastrichtian age, about 66 million years ago, though a much earlier species has also been identified from the Campanian-aged Dinosaur Park Formation of Alberta, about 75 million years ago.
Bonapartenykus is a monospecific genus of alvarezsauroid dinosaur from Argentina that lived during the Late Cretaceous (Campanian-Maastrichtian) in what is now the upper Allen Formation of the Río Negro Province. The type and only species, Bonapartenykus ultimus, is known from a nearly articulated but partial skeleton that was found in close association to two incomplete eggs and several clusters of eggshells belonging to the oogenus Arriagadoolithus. Bonapartenykus was named in 2012 by Federico L. Agnolin, Jaime E. Powell, Fernando E. Novas and Martin Kundrát. Bonapartenykus has an estimated length of 2.5 m (8.2 ft) and weight of 72 kg (159 lb), making it the largest member of the clade Alvarezsauroidea.
Brodavis is a genus of freshwater hesperornithiform birds known from the Late Cretaceous of North America and Asia. It was first described and named by Larry D. Martin, Evgeny N. Kurochkin and Tim T. Tokaryk in 2012 and assigned to a new monogeneric family, Brodavidae. Four species were described and assigned to Brodavis.
Acheroraptor is an extinct genus of dromaeosaurid theropod dinosaur known from the latest Maastrichtian Hell Creek Formation of Montana, United States. It contains a single species, Acheroraptor temertyorum. A. temertyorum is one of the two geologically youngest known species of dromaeosaurids, the other being Dakotaraptor, which is also known from Hell Creek. A basal cousin of Velociraptor, Acheroraptor is known from upper and lower jaw material.
Leptorhynchos is an extinct genus of caenagnathid theropod from the Late Cretaceous of what is now the US state of Texas, although it has been suggested to also exist in Alberta and South Dakota. The type species is L. gaddisi, and it is currently the only widely accepted valid species. The generic name of Leptorhynchos comes from the Greek "leptos" meaning "small" and "rhynchos" meaning "beak". The specific epithet is in honor of the Gaddis family, who owned the land on which the holotype was discovered.
Lamarqueavis is an extinct genus of prehistoric birds from the Cimolopterygidae known from Late Cretaceous-aged rocks from Argentina, Canada, and the United States. The type species, L. australis, was named in 2010 and is based on the holotype MML 207, a partial right coracoid found in the Allen Formation, Argentina. Two other species, L. minima, based on the holotype UCMP 53976, a right coracoid found in the Lance Formation, Wyoming, and L. petra, based on the holotype AMNH 21911, a left coracoid also found in the Lance Formation, Wyoming, were transferred over from Cimolopteryx to Lamarqueavis in 2010. A third unnamed species is known from the Dinosaur Park Formation of Alberta, Canada.
Sierraceratops is a genus of chasmosaurine ceratopsian from the Late Cretaceous Hall Lake Formation of New Mexico, United States. The genus contains a single species, Sierraceratops turneri, known from a partial skeleton discovered in 1997.
Maip is a genus of large megaraptorid theropod dinosaur from the Late Cretaceous (Maastrichtian) Chorrillo Formation of Santa Cruz, Argentina. The genus contains a single species, M. macrothorax, known from an incomplete, disarticulated skeleton. Maip may represent the largest megaraptorid known from South America, and possibly the world.
Thalassotitan is an extinct genus of large mosasaurs that lived during the late Maastrichtian of the Cretaceous period in what is now Morocco, around 66 million years ago. The only known species is T. atrox, described in 2022 from fossils discovered in the Ouled Abdoun Basin, where many other mosasaurs have been found. It was assigned to the tribe Prognathodontini alongside other mosasaurs like Prognathodon and Gnathomortis. The prognathodontines are separated from other mosasaurs based on their massive jaws and robust teeth.
