Richardoestesia is a medium-sized (about 100 kilograms (220 lb)) genus of theropod dinosaur from the late Cretaceous Period of what is now North America. It currently contains two species, R. gilmorei and R. isosceles.
|Tooth of cf. R. gilmorei with close up of denticles|
Currie, Rigby & Sloan, 1990
Currie, Rigby & Sloan, 1990
The holotype specimen of Richardoestesia gilmorei (NMC 343) consists of the pair of lower jaws found in the upper Judith River Group, dating from the Campanian age, about 75 million years ago. The jaws are slender and rather long, 193 millimeter, but the teeth are small and very finely serrated with five to six denticles per millimeter. The serration density is a distinctive trait of the species.
In 2001, Julia Sankey named a second species: Richardoestesia isosceles, based on a tooth, LSUMGS 489:6238, from the Texan Aguja Formation, which is of a longer and less recurved type. The teeth of R. isosceles have also been identified as crocodyliform in shape, possibly belonging to a sebecosuchian.
The jaws were found in 1917 by Charles Hazelius Sternberg and sons in the Dinosaur Provincial Park in Alberta at the Little Sandhill Creek site. In 1924 Charles Whitney Gilmore named Chirostenotes pergracilis and referred the jaws to this species. In the eighties it became clear that Chirostenotes was an oviraptosaur to which the long jaws could not have belonged. Therefore in 1990 Phillip Currie, John Keith Rigby and Robert Evan Sloan named a separate species: Richardoestesia gilmorei. The genus is named for Richard Estes, to honor his important work on small vertebrates and especially theropod teeth of the Late Cretaceous. The naming authors actually intended to use the spelling Ricardoestesia, Ricardus being the normal latinisation of "Richard". However, except in one overlooked figure caption, the editors of the paper altered the spelling to include the 'h'. Ironically, in 1991 George Olshevsky in a species list also used the spelling Richardoestesia, and indicated Ricardoestesia to be the misspelling, unaware that the original authors actually intended the name to be spelled this way. As a result, under ICZN rules, he acted as "first revisor" choosing between the two spelling variants of the original publication and inadvertently made the misspelt name official. Subsequently, the original authors have adopted the spelling Richardoestesia. The specific name honors Gilmore.
Richardoestesia-like teeth have been found in many Late Cretaceous geological formations, including the Horseshoe Canyon Formation, the Scollard Formation, Hell Creek Formation, Ferris Formation, and the Lance Formation (dated to about 66 million years ago). Similar teeth have been referred to this genus from as early as the Barremian age (Cedar Mountain Formation, 125 million years ago).
Because of the disparity in location and time of the many referred teeth, researchers have cast doubt on the idea that they all belong to the same genus or species. A comparative study of the teeth published in 2013 demonstrated that both R. gilmorei and R. isosceles were only definitively present in the Dinosaur Park Formation, dated to between 76.5 and 75 million years ago. R. isosceles was also present in the Aguja Formation, roughly the same age. All other referred teeth most likely belong to different species, which have not been named due to the lack of body fossils for comparison.
Asiamericana (AY-zha-MER-i-KAHN-a – (Greek: Asia meaning Asia and New Latin Americas meaning Americas) is a dubious fossil fish genus known only from isolated teeth. It was named to recognize the occurrence of similar fossil teeth in Central Asia and North America. These regions once formed a connected land mass, during the Cretaceous period and were referred to as Asiamerica.
The teeth were discovered by L. A. Nesov in 1995. The findings were based on three teeth found in the central Kyzylkum desert, Uzbekistan, in deposits of the Bissekty Formation, dated to the mid-late Turonian age of the Late Cretaceous, about 90 million years ago. They are comparable to other teeth found in Kazakhstan and North America, which have been illustrated but not formally described. The type species is A. asiaticus.
The teeth themselves are straight, lack a constriction at the base, and lack serrations.Camadas de Guimarota
The Camadas de Guimarota, simply Guimarota, or Camadas de Alcobaça is a disused coal mine near the city of Leiria in central Portugal. An important geological formation dating back to the Kimmeridgian age of the Late Jurassic period, it contains a diverse array of fossil animals and plants, including dinosaurs and mammals.
The locality was extensively worked by paleontologists from the Free University of Berlin, but this activity stopped in 1982. Further excavations are considered to be unlikely, since the mine is now flooded. Pumping it out and rendering it safe again would be prohibitively expensive.
The mammal remains from this site are of particular note. The excavations were so successful that many of the recovered remains have yet to be studied.Coelurosauria
Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.
Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyrannosaurs, ornithomimosaurs, and maniraptorans; Maniraptora includes birds, the only dinosaur group alive today.Most feathered dinosaurs discovered so far have been coelurosaurs. Philip J. Currie considers it likely and probable that all coelurosaurs were feathered. In the past, Coelurosauria was used to refer to all small theropods, but this classification has since been abolished.Foremost Formation
The Foremost Formation is a stratigraphic unit of Late Cretaceous (Campanian) age that underlies much of southern Alberta, Canada. It was named for outcrops in Chin Coulee near the town of Foremost and is known primarily for its dinosaur remains and other fossils.Fort Crittenden Formation
The Fort Crittenden Formation is a geological formation in Arizona whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Kirtlandian
The Kirtlandian is a North American land-vertebrate faunal age of the Cretaceous period, following the Judithian and succeeded by the Edmontonian. It lasted about 2 million years, ca 74.8 to 72.8 Mya and is characterized by the ceratopsian Pentaceratops sternbergii, which lived throughout the Kirtlandian. It was first named by R.M. Sullivan and S.G. Lucas in 2003 as a faunal age for the Kirtland and Fruitland formations. Previously, only five land-vertebrate ages were identified from the Late Cretaceous. as identified by Loris S. Russell in 1975, they include the Paluxian, Aquilan, Judithian, Edmontonian, and the Lancian. Before the naming of the Kirtlandian, three gaps, between the Paluxian and Aquilan, the Aquilan and the Judithian, and the Judithian and Edmontonian, were identified but not named.
The Fruitland Formation measures 97 to 107 metres (318 to 351 ft) thick, and with the 594 metres (1,949 ft) of the Kirtland Formation, the Kirtlandian consists of 701 metres (2,300 ft) of sediments. The rock types within the formations are primarily coal beds, but also include sandstone, siltstone, mudstone, and shale. Within the sediments with a Kirtlandian age, two local faunas, the Hunter Wash local fauna, and the Willow Wash local fauna, have been identified. The currently accepted date of the Kirtlandian is 74.8 to 72.8 million years ago.List of the Mesozoic life of Montana
This list of the Mesozoic life of Montana contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of Montana and are between 252.17 and 66 million years of age.List of the Mesozoic life of South Dakota
This list of the Mesozoic life of South Dakota contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of South Dakota and are between 252.17 and 66 million years of age.List of the Mesozoic life of Utah
This list of the Mesozoic life of Utah contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of Utah and are between 252.17 and 66 million years of age.List of the prehistoric life of Montana
This list of the prehistoric life of Montana contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of Montana.List of the prehistoric life of North Dakota
This list of the prehistoric life of North Dakota contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of North Dakota.List of the prehistoric life of South Dakota
This list of the prehistoric life of South Dakota contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of South Dakota.Lourinhã Formation
The Lourinhã Formation is a fossil rich geological formation in western Portugal, named for the municipality of Lourinhã. The formation is Late Jurassic in age (Kimmeridgian/Tithonian) and is notable for containing a fauna similar to that of the Morrison Formation in the United States and the Tendaguru beds in Tanzania. The stratigraphy of the formation and the basin in general is disputed, with the constituent member beds belonging to the formation varying between different authorsBesides the fossil bones, Lourinhã Formation is well known for the fossil tracks and fossilized dinosaur eggs.The Lourinhã Formation includes several lithostratigraphic units, such as Praia da Amoreira-Porto Novo Members and the Sobral Unit.Montanoceratops
Montanoceratops is an extinct genus of small ceratopsian dinosaur that lived approximately 70 million years ago during the latter part of the Cretaceous Period in what is now Montana and Alberta. Montanoceratops was a small sized, moderately-built, ground-dwelling, quadrupedal herbivore, that could grow up to an estimated 3 m (9.8 ft) long.Ojo Alamo Formation
The Ojo Alamo Formation is a geologic formation spanning the Mesozoic/Cenozoic boundary. Dinosaur remains are among the fossils that have been recovered from the formation, though all dinosaur remains come from the lowest part of the formation, the Naashoibito member (sometimes considered part of the Kirtland Formation, which dates to the late Maastrichtian stage of the Cretaceous period.The Ojo Alamo formation is divided into two subunits separated by a large unconformity—a gap in the geologic record. The lower Naashoibito member (sometimes considered part of the Kirtland Formation) was deposited during the Maastrichtian age of the Cretaceous period, specifically between about 69-68 million years ago. It overlies the De-na-zin member of the Kirtland formation, though the two are separated by another large unconformity that spans 73-69 million years of geologic time. All dinosaur fossils probably come from this unit.The upper unit of the Ojo Alamo Formation is the Kimbeto Member, which was deposited mainly during the earliest Cenozoic (Danian age of the Paleogene period), between 66 and 64 million years ago. Some researchers have claimed to find isolated non-avian dinosaur remains in this younger unit. If this is the case, it would represent the only known instance of a non-avian dinosaur population persisting after the Cretaceous–Paleogene extinction event. However, most scientists consider these to have been stratigraphically misinterpreted or reworked from the older Naashoibito member.Pachyrhinosaurus
Pachyrhinosaurus (meaning in Greek "thick-nosed lizard", from Παχυ (pachy), thick; ρινό (rinó), nose; and σαυρος (sauros), lizard) is an extinct genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species have been found in Alberta and Alaska. A great number were not available for study until the 1980s, resulting in a relatively recent increase of interest in Pachyrhinosaurus.
Three species have been identified. P. lakustai, from the Wapiti Formation, the bonebed horizon of which is roughly equivalent age to the upper Bearpaw and lower Horseshoe Canyon Formations, is known to have existed from about 73.5-72.5 million years ago. P. canadensis is younger, known from the lower Horseshoe Canyon Formation, about 71.5-71 Ma ago and the St. Mary River Formation. Fossils of the youngest species, P. perotorum, have been recovered from the Prince Creek Formation of Alaska, and date to 70-69 million years ago. The presence of three known species makes this genus the most speciose among the centrosaurines.Paronychodon
Paronychodon (meaning "beside claw tooth") was a theropod dinosaur genus. It is a tooth taxon, often considered dubious because of the fragmentary nature of the fossils, which include "buckets" of teeth but no other remains.
The type species, named by Edward Drinker Cope in 1876, is Paronychodon lacustris, from the Judith River Formation of Montana, dating to 75 million years ago, during the Campanian stage. The holotype is specimen AMNH 3018. It is a tooth about one centimetre long, elongated, recurved, lacking serrations, possessing low vertical ridges and with a D-shaped cross-section, the inner side being flattened. Cope at first thought the tooth belonged to a plesiosaur, but the same year realised it represented a carnivorous dinosaur.A second species, Paronychodon caperatus, is known from the Hell Creek Formation of North Dakota, Montana, and South Dakota and Lance Formation of Wyoming (latest Maastrichtian stage, 66 million years ago) and was originally referred to the mammal genus Tripriodon by Othniel Charles Marsh in 1889, but placed in Paronychodon by George Olshevsky in 1991. It is based on holotype YPM 10624, a tooth close in form to the holotype of P. lacustris but somewhat larger. In 1995 Olshevsky renamed Laelaps explanatus Cope 1876 into a Paronychodon explanatus; today the taxon is seen as based on Saurornitholestes teeth.
A very large number of other specimens matching these teeth in some or all aspects of their anatomy have been referred to Paronychodon. Some of these included serrated teeth, low teeth and teeth without a flattened side. These teeth of the general "Paronychodon" type have been reported from a wide variety of times and places, including the Early Cretaceous Una Formation of Spain, dating to the late Barremian age 125 million years ago.
Paronychodon has been considered a coelurid, an ornithomimosaur, a dromaeosaurid, an archaeopterygid, and a troodontid, though it could also be another kind of coelurosaurian theropod. While most researchers have therefore considered it simply represents indeterminate theropod teeth, a small consensus has found them to be Deinonychosauria. The teeth assigned to Paronychodon are all small, and may have come from various juvenile deinonychosaurs. Jaws from adult individuals bearing identical teeth have never been found. Marsh already suggested such teeth were pathological, having formed when the first teeth of the lower jaws by accident grew back-to-back to each other on the mandible suture. Philip J. Currie in 1990 also concluded to a malformation, thinking the flattened side resulted from the tooth remaining attached too long to the inner wall of the tooth-socket. Serrated specimens of the type would thus simply be deviant dromaeosaurid teeth; however, unserrated teeth might represent a separate taxon or taxa. One study, by Sunny Hwang, showed that the tooth enamel is identical to that found in Byronosaurus, a troodontid known from juveniles with serration-less teeth.Several taxa have on occasion been considered synonyms of Paronychodon, though there is little consensus. Paronychodon was in 1876 by Cope described as being similar to Zapsalis, another tooth taxon, itself often considered synonymous with Richardoestesia, a possible dromaeosaurid. Richardoestesia isosceles would, according to a study by Julia Sankey e.a., be synonymous with the elongated, so-called "Type A", teeth of Paronychodon, to which also the Paronychodon holotype belongs. The Eurasian Euronychodon tooth genus is also sometimes considered a (junior) synonym of Paronychodon.Udurchukan Formation
The Udurchukan Formation is a geological formation located in Amur Region, Far East Russia. Based on palynomorphs such as Wodehouseia spinata the Udurchukan is considered of Maastrichtian age of the Late Cretaceous, during the Cretaceous Period.