Troodon is a former wastebasket taxon and a potentially dubious genus of relatively small, bird-like theropod dinosaurs definitively known from the Campanian age of the Late Cretaceous period. It includes at least one species, Troodon formosus, known from Montana. Discovered in October 1855, T. formosus was among the first dinosaurs found in North America, although it was thought to be a lizard until 1877. Several well-known troodontid specimens from the Dinosaur Park Formation in Alberta were once believed to be members of this genus. However, recent analyses in 2017 have found this genus to be undiagnostic and referred some of these specimens to the genus Stenonychosaurus some to the genus Latenivenatrix, and some to the genus Pectinodon. The genus name is Ancient Greek for "wounding tooth", referring to the teeth, which were different from those of most other theropods known at the time of their discovery. The teeth bear prominent, apically oriented serrations. These "wounding" serrations, however, are morphometrically more similar to those of herbivorous reptiles, and suggest a possibly omnivorous diet.
Archelon is an extinct marine turtle from the Late Cretaceous, and is the largest turtle ever to have been documented, with the biggest specimen measuring 4.6 m (15 ft) from head to tail and 2.2–3.2 t in body mass. It is known only from the Pierre Shale and has one species, A. ischyros. In the past, the genus also contained A. marshii and A. copei, though these have been reassigned to Protostega and Kansastega, respectively. The genus was named in 1895 by American paleontologist George Reber Wieland based on a skeleton from South Dakota, who placed it into the extinct family Protostegidae. The leatherback sea turtle was once thought to be its closest living relative, but now, Protostegidae is thought to be a completely separate lineage from any living sea turtle.
Vegavis is a genus of extinct bird that lived during the Late Cretaceous of Antarctica, some 68 to 66 mya. Among modern birds, most studies show that Vegavis is most closely related to ducks and geese (Anatidae), but it is not considered to be a direct ancestor of them, although other studies question these results.
Ichthyornis is an extinct genus of toothy seabird-like ornithuran from the late Cretaceous period of North America. Its fossil remains are known from the chalks of Alberta, Alabama, Kansas, New Mexico, Saskatchewan, and Texas, in strata that were laid down in the Western Interior Seaway during the Turonian through Campanian ages, about 95–83.5 million years ago. Ichthyornis is a common component of the Niobrara Formation fauna, and numerous specimens have been found.
Hesperornis 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.
Hornby Island of British Columbia, Canada, is one of the two northernmost Gulf Islands, the other being Denman Island. It is located near Vancouver Island's Comox Valley,
Caenagnathus is a genus of caenagnathid oviraptorosaurian dinosaur from the late Cretaceous period. It is known from partial remains including lower jaws, a tail vertebra, hand bones, and hind limbs, all found in the Dinosaur Park Formation of Alberta, Canada. Caenagnathus measured about 2.5 m (8.2 ft) long and weighed about 96–100 kg (212–220 lb).
Baptornis is a genus of flightless, aquatic birds from the Late Cretaceous, some 87-80 million years ago. The fossils of Baptornis advenus, the type species, were discovered in Kansas, which at its time was mostly covered by the Western Interior Seaway, a shallow shelf sea. It is now known to have also occurred in today's Sweden, where the Turgai Strait joined the ancient North Sea; possibly, it occurred in the entire Holarctic.
Polarornis is a genus of prehistoric bird, possibly an anserimorph. It contains a single species Polarornis gregorii, known from incomplete remains of one individual found on Seymour Island, Antarctica, in rocks which are dated to the Late Cretaceous.
The Bearpaw Formation, also called the Bearpaw Shale, is a geologic formation of Late Cretaceous (Campanian) age. It outcrops in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, and was named for the Bear Paw Mountains in Montana. It includes a wide range of marine fossils, as well as the remains of a few dinosaurs. It is known for its fossil ammonites, some of which are mined in Alberta to produce the organic gemstone ammolite.
Plioplatecarpus is a genus of mosasaur lizard. Like all mosasaurs, it lived in the late Cretaceous period, about 73-68 million years ago.
Asiahesperornis is a prehistoric foot-propelled diving toothed flightless bird genus from the Late Cretaceous. The single known species is Asiahesperornis bazhanovi. It lived in what today is Kazakhstan, at its time the shores of the shallow Turgai Sea.
Ornithurae is a natural group which includes the common ancestor of Ichthyornis, Hesperornis, and all modern birds as well as all other descendants of that common ancestor.
Desmatochelys is an extinct genus of sea turtles belonging to the family Protostegidae. This genus contains two known species, D. lowii and D. padillai. D. lowii was first discovered in 1895, followed by D. padillai in 2015. Having been estimated at over 120 million years old, D. padillai is currently the oldest known species of sea turtle.
Kourisodon is an extinct genus of mosasaur. Fossils have been found from Vancouver Island in British Columbia, Canada, as well as from the Izumi Group of Japan. These finds date back to the late Santonian stage and the late Campanian to the late Maastrichtian, respectively, of the Late Cretaceous. Kourisodon was originally described as a member of the "Leiodontini", more recently as a "Clidastine".
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.
The Northumberland Formation is a Late Cretaceous (?Campanian-?Maastrichtian)-aged geologic formation in Canada. It belongs to the larger Nanaimo Group. Indeterminate bird and pterosaur fossils have been recovered from the formation, as well as a potential gladius of Eromangateuthis. An extensive diversity of shark teeth is known from the formation; many appear to be closely allied with modern deep-water shark taxa, suggesting a deep-water environment for the formation. The most well-known exposures of the formation are on Hornby Island.
Tingmiatornis is a genus of flighted and possibly diving ornithurine dinosaur from the High Arctic of Canada. The genus contains a single species, T. arctica, described in 2016, which lived during the Turonian epoch of the Cretaceous.
Vegaviidae is an extinct family of ornithurine dinosaurs, often regarded as primitive anseriforms, which existed during the Late Cretaceous and possibly the Paleocene. Fossils attributed to the family have been found in Canada, Chile, New Zealand, and Antarctica.
Natovenator is a genus of halszkaraptorine dromaeosaurid dinosaur from the Late Cretaceous Barun Goyot Formation of Mongolia. The genus is known from a single species, N. polydontus. Natovenator is crucial to the understanding of halszkaraptorines due to it providing more support for the semi-aquatic lifestyle that has been proposed for this clade. This discovery is important as the semi-aquatic lifestyles of halszkaraptorines was contested in early 2022.
