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The Lancian was a North American faunal stage of the Late Cretaceous. It was the final stage of the Cretaceous period in North America, lasting from approximately 70.6 to 66 million years ago.
Terrestrial sedimentary strata from the Judithian to the Lancian are generally regressive throughout the entire sequence, so the preserved changes in fossil communities represent not only phylogenetic changes but ecological zones from the submontane habitats to near-sea level coastal habitats. [1]
By the Lancian, the crested hadrosaurs are no longer the dominant inhabitant of any province of western North America; the only remaining species was Hypacrosaurus . [2] Lehman records three surviving chasmosaurs, Triceratops, Torosaurus and Nedoceratops , with the possibility of the recently discovered Ojoceratops, Regaliceratops and Bravoceratops . [2] It has recently been suggested that Triceratops and Torosaurus may be synonymous, though this is still up for debate. Saurolophine dinosaurs like Edmontosaurus , Kritosaurus , Saurolophus as well as the recently discovered Augustynolophus were some of the known surviving hadrosaurs. [2] All lacked the elaborate ornamentation of their predecessors, the lambeosaurs. [2] The ankylosaurs had been reduced to down to a handful of species, with ankylosaurs like Anodontosaurus and Ankylosaurus , as well as nodosaurs like Denversaurus , Edmontonia and Glyptodontopelta being the only known survivors. In the south the transition to the Lancian is even more dramatic, which Lehman describes as "the abrupt reemergence of a fauna with a superficially "Jurassic" aspect." [2] These faunas are dominated by Alamosaurus and feature abundant Quetzalcoatlus, Bravoceratops and Ojoceratops in Texas. [3]
The extreme changes occurring in the make-up of herbivore communities during the faunal turnover suggests that a change in the ecosystems' flora was "the most immediate cause...though perhaps not the ultimate one." [4] The rapid expansion of land and drying of inland climate accompanying a drop in sea level could explain some of the environmental changes occurring Late Cretaceous western North America. [5] The wetland habitat enjoyed by many dinosaurs would have shrunk and fragmented. [5] Since many species had very limited geographic ranges its plausible that some of the fragments would be smaller than the area needed to support the species. [5] However, there's no direct evidence for the shrinking of wetland environments. [5] Lehman contends that the actual area of coastal lowlands within 150m of the shoreline must have actually increased significantly. [5] Further, dinosaurs that inhabited inland or arid environments were among the most prevalent in the Lancian. [5] The Alamosaurus-Quetzalcoatlus association probably represent semi-arid inland plains. [5] In previous research Jack Horner speculated that a rise in sea level during the Bearpaw Transgression created selective pressure as coastal lowlands were swallowed up the sea, resulting in anagenesis. [6] If the geographic range of some dinosaur species were truly as limited as the fossil record suggests, then a rapid rise and in sea level could cause intense pressure even the event was local. [6] Additionally, a rapid drop in sea level could allow for "rapid colonization by a few dinosaur generalists." [6]
The appearance or reappearance of basal neoceratopsians could be explained by immigration from Asia. [6] Dinosaurs like Nodocephalosaurus resembled Asian forms, and some like Saurolophus co-occurred in Asia as well as North America. [6] Potential Asian immigrants were especially common in upland environments. [6] The appearance of Alamosaurus may have represented an immigration event from South America. [6] Some taxa may have co-occurred on both continents, including Kritosaurus and Avisaurus . [6] Alamosaurus appears and achieves dominance in its environment very abruptly. [6] Some scientists speculated that Alamosaurus was an immigrant from Asia. [6] Inhabitants of upland environment are more likely to be endemic than coastal species, and tend to have less of an ability to cross bodies of water. [6] Further, early Cretaceous titanosaurs were already known, so North American potential ancestors for Alamosaurus already existed. [6] Quetzalcoatlus also had precursors in North America and its apparent range expansion may represent the expansion of its preferred habitat rather than an immigration event. [6] Early Cretaceous deposits in North America reveal that basal neoceratopsians were already present on the continent before their apparent reemergence in the Lancian, so an immigration event from Asia is unnecessary to explain their appearance. [6] The major potential immigrants represent archaic forms that probably wouldn't have directly competed with the disappearing forms anyway. [7] Lehman described the evidence for immigration as a driving force in Lancian dinosaur faunal turnovers as "not particularly compelling." [6]
The faunal turnover may be explained by the descent of more primitive forms existing in upland refugia characterized by conifer-dominated flora into areas that were formerly coastal lowlands as the seas retreated and conditions became more arid. [8]
The decline of mammal diversity in Western North America from the Miocene to the present primarily effected large herbivores and occurred over roughly the same length of time as the Late Cretaceous changes, and so may be parallel. [9] They have many commonalities, including the replacement of diverse with single species environments (caribou in the north, bison to the south). [9] The most spectacular and specialized forms became extinct. [9] The mammalian turnover was preceded by an episode of immigration, [9] and was associated with the rapid expansion of terrestrial habitat due to melting glaciers. [9] In the mammalian turnover, the newly emerging dominant fauna were clearly Old World immigrants, the cervids and bovids. [10]
In the southern biome, by Lancian time sauropods had replaced both hadrosaurs and ceratopsians. [11] In the north, both were still present although hadrosaurs were demoted to a "subordinate" role in dinosaur ecosystems. [11] Edmontosaurus was the dominant northern hadrosaurid. [11] At the end of the Cretaceous, most ecosystems were dominated by a single herbivore. [11] The northern biome was dominated by Triceratops and the southern biome by Alamosaurus. [11] This faunal turnover coincides with the Laramide orogeny and the uplift of the central Rockies. [11] Strata exhibit changes in lithology and the direction of paleocurrents, and a severe drop in relative sea level. [11] At the very least, Lehman argues, the altitudinal life zones would shift, and a change in the distribution of vegetation utilized by herbivorous dinosaurs would have probably resulted. [11] By the end of the Judithian, North America had 7.7 million km2 of land area, but by the end of the Lancian it had reached 17.9 million km2, nearly the modern value of 22.5 million km2. [11]
Quetzalcoatlus is a pterosaur known from the Late Cretaceous period of North America ; it was one of the largest known flying animals of all time. Quetzalcoatlus is a member of the family Azhdarchidae, a family of advanced toothless pterosaurs with unusually long, stiffened necks. Its name comes from the Aztec feathered serpent god, Quetzalcoatl, in Nahuatl. The type species is Q. northropi, named by Douglas Lawson in 1975; the genus also includes the smaller species Q. lawsoni, which was known for many years as an unnamed species before being named by Brian Andres and Wann Langston Jr. (posthumously) in 2021.
Ceratopsidae is a family of ceratopsian dinosaurs including Triceratops, Centrosaurus, and Styracosaurus. All known species were quadrupedal herbivores from the Upper Cretaceous. All but one species are known from western North America, which formed the island continent of Laramidia during most of the Late Cretaceous. Ceratopsids are characterized by beaks, rows of shearing teeth in the back of the jaw, elaborate nasal horns, and a thin parietal-squamosal shelf that extends back and up into a frill. The group is divided into two subfamilies—Chasmosaurinae and Centrosaurinae. The chasmosaurines are generally characterized by long, triangular frills and well-developed brow horns. The centrosaurines had well-developed nasal horns or nasal bosses, shorter and more rectangular frills, and elaborate spines on the back of the frill.
Maiasaura is a large herbivorous saurolophine hadrosaurid ("duck-billed") dinosaur genus that lived in the area currently covered by the state of Montana and the province Alberta, Canada in the Upper Cretaceous Period, about 76.7 million years ago.
Kritosaurus is an incompletely known genus of hadrosaurid (duck-billed) dinosaur. It lived about 74.5-66 million years ago, in the Late Cretaceous of North America. The name means "separated lizard", but is often mistranslated as "noble lizard" in reference to the presumed "Roman nose".
Alamosaurus is a genus of opisthocoelicaudiine titanosaurian sauropod dinosaurs, containing a single known species, Alamosaurus sanjuanensis, from the late Cretaceous Period of what is now southern North America. Isolated vertebrae and limb bones indicate that it reached sizes comparable to Argentinosaurus and Puertasaurus, which would make it the largest dinosaur known from North America. Its fossils have been recovered from a variety of rock formations spanning the Maastrichtian age of the late Cretaceous period. Specimens of a juvenile Alamosaurus sanjuanensis have been recovered from only a few meters below the Cretaceous-Paleogene boundary in Texas, making it among the last surviving non-avian dinosaur species.
Arrhinoceratops is a genus of herbivorous ceratopsian dinosaur. The name was coined as its original describer concluded it was special because the nose-horn was not a separate bone, however further analysis revealed this was based on a misunderstanding. It lived during the latest Campanian/earliest Maastrichtian stage of the Late Cretaceous, predating its famous relative Triceratops by a few million years, although it was contemporary with Anchiceratops. Its remains have been found in Canada.
The Hell Creek Formation is an intensively studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana. The formation stretches over portions of Montana, North Dakota, South Dakota, and Wyoming. In Montana, the Hell Creek Formation overlies the Fox Hills Formation. The site of Pompeys Pillar National Monument is a small isolated section of the Hell Creek Formation. In 1966, the Hell Creek Fossil Area was designated as a National Natural Landmark by the National Park Service.
Amurosaurus is a genus of lambeosaurine hadrosaurid dinosaur found in the latest Cretaceous period of eastern Asia. Like most lambeosaurs, it would have been a primarily bipedal herbivore with a "duckbill" shaped snout and a hollow crest on top of its head, although such a crest has not been found. Fossil bones of adults are rare, but an adult would most likely have been at least 6 metres (20 ft) long. According to Gregory S. Paul, it was about 8 metres (26 ft) long and weighed about 3,000 kilograms (6,600 lb).
The Edmontonian was a North American faunal epoch occurring during the Late Cretaceous, lasting from approximately 70 to 68 million years ago.
The Aguja Formation is a geological formation in North America, exposed in Texas, United States and Chihuahua and Coahuila in Mexico, whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.
The Javelina Formation is a geological formation in Texas. Dating has shown that the strata date to the Maastrichtian stage of the Late Cretaceous, approximately 70 to 66.5 million years old. The middle part of the formation has been dated to about 69 million years ago plus or minus 1 Ma and the top situated near the Cretaceous–Paleogene boundary, dated to 66 Ma ago. Dinosaur remains are among the fossils that have been recovered from the formation.
Dinosaur Train is a computer-animated musical children's television series created by Craig Bartlett, who created Nickelodeon's Hey Arnold!. The series features a curious young Tyrannosaurus rex named Buddy who, together with his adopted Pteranodon family, takes the Dinosaur Train to explore his time period, and have adventures with a variety of dinosaurs. It is co-produced by The Jim Henson Company in association with the Info-communications Media Development Authority, Sparky Animation, FableVision, Snee-Oosh, Inc., Reel FX, and Sea to Sky Entertainment. As of September 2018, PBS Kids had ordered 11 more episodes, taking the total number of episodes to 100. A film based on the series from Universal Pictures and Universal 1440 Entertainment titled, Dinosaur Train: Adventure Island premiered on April 12, 2021.
Ojoceratops is a genus of ceratopsian dinosaur which lived in what is now New Mexico, United States. Ojoceratops fossils have been recovered from strata of the Ojo Alamo Formation, dating to the late Cretaceous period. The type species is Ojoceratops fowleri. It is very similar to its close relative Triceratops, though it is from an earlier time period and has a more squared-off frill. Nick Longrich, in 2011, noted that the squared-off frill is also found in some true Triceratops specimens and that Ojoceratops is probably a junior synonym of Triceratops, while Holtz (2010) noted that it is probably ancestral to Triceratops and possibly synonymous with the contemporary Eotriceratops.
Last Day of the Dinosaurs is a 2010 Discovery Channel television documentary about the extinction of the dinosaurs. It portrays the Alvarez hypothesis as the cause of extinction. The documentary was released on August 28, 2010 and narrated by Bill Mondy.
Titanoceratops is a controversial genus of herbivorous ceratopsian dinosaur. It was a giant chasmosaurine ceratopsian that lived in the Late Cretaceous period in what is now New Mexico. Titanoceratops was named for its large size, being one of the largest known horned dinosaurs and the type species was named T. ouranos, after Uranus (Ouranos), the father of the Greek titans. It was named in 2011 by Nicholas R. Longrich for a specimen previously referred to Pentaceratops. Longrich believed that unique features found in the skull reveal it to have been a close relative of Triceratops, classified within the subgroup Triceratopsini. However, other researchers have expressed skepticism, and believe "Titanoceratops" to simply be an unusually large, old specimen of Pentaceratops.
Dinosaur paleobiogeography is the study of dinosaur geographic distribution, based on evidence in the fossil record.
The Judithian was a North American faunal stage lasting from 83.5 to 70.6 million years ago. It overlaps with the Campanian global stage.
This timeline of hadrosaur research is a chronological listing of events in the history of paleontology focused on the hadrosauroids, a group of herbivorous ornithopod dinosaurs popularly known as the duck-billed dinosaurs. Scientific research on hadrosaurs began in the 1850s, when Joseph Leidy described the genera Thespesius and Trachodon based on scrappy fossils discovered in the western United States. Just two years later he published a description of the much better-preserved remains of an animal from New Jersey that he named Hadrosaurus.
Dineobellator is a genus of dromaeosaurid theropod dinosaur that lived in North America during the Late Cretaceous period. The remains have been found in the Maastrichtian stage of the Naashoibito Member at the Ojo Alamo Formation, New Mexico.
