The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the Jurassic period.
The fauna of Morrison Formation is similar to one in the coeval rocks of Tendaguru Beds (in Tanzania) and Lourinhã Formation in Portugal, [1] mostly with the second. Some genera are shared in Morrison and Lourinhã, such as Torvosaurus , [2] Ceratosaurus , [3] Stegosaurus , Dryosaurus , [4] and Allosaurus . [5] In sum, Morrison Fm has 37 valid genera of dinosaurs.
The herbivorous ornithischian dinosaurs were diverse but not as common as sauropods in the Morrison. Fruitadens , previously known as the "Fruita Echinodon ", was found to be a heterodontosaurid. Plate-backed stegosaurids included Hesperosaurus mjosi , Stegosaurus ungulatus , S. stenops, and Alcovasaurus longispinus . Armored dinosaurs that weren't stegosaurs were unknown in the formation until the 1990s. Two have been named: Gargoyleosaurus parkpinorum and Mymoorapelta maysi . Ornithopods, bipedal herbivores, came in several types. Small "hypsilophodonts" included Drinker nisti , Laosaurus celer , "L." gracilis, Nanosaurus agilis , Othnielia rex , and Othnielosaurus consors (all of which are now synonymous with Nanosaurus). Larger but similar-looking dryosaurids were represented by two species of Dryosaurus (D. altus and D. elderae) and the camptosaurid Uteodon aphanoecetes , which is currently known only from Dinosaur National Monument. Still larger was the more common Camptosaurus dispar . Dryosaurids and camptosaurids were early iguanodonts, a group that would later spawn the duck-billed dinosaurs.
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| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
Colorado [6] | Morrison Anomoepus lack the handprint impressions found associated with earlier instances of the ichnogenus in New England. [6] | ||||
C. amplus [8] | Now known to be based on a theropod foot. [10] | ||||
C. aphanoecetes [11] | Utah, Brushy Basin member [11] | Reclassified as Uteodon . | |||
C. browni [12] | Junior synonym of C. dispar. [13] | ||||
"[Twenty-five to thirty] disarticulated skull elements, some with associated postcrania, approximately [ten] partial, articulated skeletons, juvenile to adult." [18] | A member of Camptosauridae. Junior synonyms include Camptosaurus browni, C. medius, and C. nanus. | ||||
C. medius [12] | Junior synonym of C. dispar. [13] | ||||
C. nanus [12] | Junior synonym of C. dispar. [13] | ||||
Utah, Saltwash member [6] | Multiple Dinehichnus trackways have been discovered. The tracks run parallel to one another, indicating that the trackmaker was at least somewhat of a social animal. [6] | Dinehichnus are attributed to dryosaurids. The tracks preserve feet characterized by widely splayed toes and that are rotated somewhat toward the midline of the trackmaker's body. Each track is accompanied by "distinct ... heel impressions". [6] | |||
D. nisti [19] | "Partial skull and postcranial skeleton." [21] | A basal neornithischian about 2 m long, slightly smaller than Othnielosaurus . [19] Junior synonym of Nanosaurus agilis [22] | |||
D. altus [14] | Colorado and Wyoming, Brushy Basin member [16] [23] [9] [24] [25] | The remains of many individuals have been uncovered, with some sites containing hundreds of bones from Dryosaurus of multiple age groups. [23] | A large dryosaurid iguanodont up to 2.4 m (7.9 feet) long and 114 kg (251 lbs) in weight. It was physically similar to Othnielosaurus , although larger and with more derived teeth. [24] | ||
D. elderae [22] | A 2 partial skeletons, one a juvenile, and 2 additional fragmentary specimens. | A large dryosaurid iguanodont up to 2.4 m (7.9 feet) long and 114 kg (251 lbs) in weight. It was physically similar to Othnielosaurus , although larger and with more derived teeth. [24] | |||
L. altus | Now known as Dryosaurus altus | ||||
L. celer | Wyoming [9] | Considered dubious due to fragmentary remains. | |||
L. consors | Now known as Othnielosaurus consors | ||||
"L. gracilis" | Considered dubious due to fragmentary remains. | ||||
N. agilis | A small basal Neornithischian known from dozens of individuals. [22] The holotype, YPM VP 1913, is a fragmentary skeleton from a juvenile. [22] | ||||
O. rex [27] | Based on an isolated femur. [27] | A small neornithischian 2 m in length. Dubious; many remains historically assigned to this taxon are now place within Nanosaurus. | |||
O. consors | A basal neornithischian about 2 m long. Junior synonym of Nanosaurus agilis [22] | ||||
P. coloradensis [28] | Colorado, Salt Wash member [28] | Eggshell present in great abundance at the so-called "Young Egg Locality" which seems to have been a dinosaur nesting ground. [28] Congeneric eggshell fossils are found at additional Colorado sites including the Fruita Paleontological Area, the Uravan Locality and Garden Park. [28] | P. coloradensis is described by John Foster as being "of the prismatic basic type," [28] with subspherical eggs about 10 cm (4 inches) in diameter. [29] This oospecies has been attributed to "hypsilophodontid" dinosaurs, although a lack of associated embryo material currently makes confirming the egg-layer's identity impossible. [28] | ||
T. aequifacies | Colorado [16] | 2 partial dorsal centra of a juvenile. | |||
T. lucasanus | Colorado [16] | 2 partial dorsal centra. | |||
U. aphanoecetes [11] | Utah, Brushy Basin member [11] | An articulated postcranial skeleton. | Sometimes synonymized with Camptosaurus. [22] | ||
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
G. parkpinorum [30] | Wyoming [9] | "Skull [and] partial postcranium." [31] | A polacanthine nodosaur known from reasonably complete fossil remains. Its skull measures 29 centimeters (11 in) in length, and its total body length is an estimated 3 to 4 meters (9.8 to 13.1 ft.). It may have weighed as much as 1 tonne (2,200 lb.). [30] | ||
M. maysi [16] | "Skull fragments, portions of [three] skeletons, [and] other postcrania." [33] | Both the first ankylosaur discovered in the formation and the first known North American Jurassic ankylosaur. [34] It probably weighed 500 kg (1,102 lbs) in life. [34] | |||
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| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
A. longispinus | "Fragmentary postcranial skeleton, adult." [36] | A dacentrurinae stegosaurid physically similar to Stegosaurus stenops but with much larger tail spines. [37] It is also similar to Kentrosaurus in having long dermal spikes on the caudal region. [35] The thighbone length was determined at 1082 millimeters. The longest spike was 86 centimeters long. Its point was broken and it is estimated the original length of the bone core at 985 millimeters. In 2019, the genus Alcovasaurus was considered a junior synonym of Miragaia [38] | |||
H. mjosi [39] | Wyoming [9] | "Complete skeleton with skull, subadult." [40] Known only from a single specimen. [39] | A stegosaurine stegosaurid that was slightly smaller and more primitive than Stegosaurus itself. H. mjosi had a broader skull and longer, lower plates. Considered by some to be a species of Stegosaurus [41] | ||
Utah [42] | Stegopodus represent only a portion of the Morrison's stegosaur tracks, which are already rare and generally only preserve the animal's hind feet. [42] | Stegosaur tracks which record front feet with five digits and hind feet with three weight-bearing digits. [42] The general morphology of the tracks fit scientific predictions made eight years in advance of the erection of Stegopodus. [42] | |||
S. armatus [14] | Several caudal vertebrae and assorted fragmentary postcranial elements. [43] | S. armatus is both the first Stegosaurus to be discovered and the type species. [44] Its type specimen is poorly preserved, incomplete, and lacks diagnostic features. [43] It has been considered dubious, with S. stenops as the neotype species for the genus. [43] | |||
S. stenops [14] | Colorado, Utah and Wyoming, Brushy Basin member [16] [14] [9] [45] | "[Two] complete skeletons with skulls, [four] braincases, at least [fifty] partial postcrania, juvenile to adult." [36] | The best known Stegosaurus species, it has shorter limbs and larger plates than S. ungulatus. [46] | ||
S. sulcatus [14] | Wyoming [47] | Several postcranial elements, including a possible shoulder spike. [43] | Often considered synonymous with S. stenops, [48] it may be distinct. Potentially has a shoulder spike, otherwise unknown in Stegosaurus, despite presence in relatives. [43] | ||
S. ungulatus [14] | Several partial skeletons, including a partial braincase. [43] | S. ungulatus had longer limbs and comparatively smaller plates than the better known S. stenops. [49] Although formerly portrayed with eight tail spikes, it is now known to have had the typical four. [50] Possibly synonymous with S. stenops. [41] | |||
Indeterminate. [51] | |||||
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| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
F. haagarorum [52] | Colorado, Brushy Basin member [53] | A partial skull and mandible with several postcranial elements. [54] | |||
Sauropods, the giant long-necked long-tailed four-legged herbivorous dinosaurs, are among the most common and famous Morrison fossils. A few have uncertain relationships, like "Apatosaurus" minimus (possibly a basal titanosauriform) and Haplocanthosaurus . Sauropods including Haplocanthosaurus priscus , H. delfsi, and the diplodocid Brontosaurus yahnahpin appeared in the early stages of the Morrison. The middle stages were dominated by familiar forms such as the giraffe-like Brachiosaurus altithorax , which were uncommon, but related camarasaurids, like Camarasaurus supremus , C. grandis, C. lentus, and Cathetosaurus/Camarasaurus lewisi , were very common. Also common were long, low diplodocids, like Apatosaurus ajax , A. louisae, Brontosaurus excelsus, B. parvus, Barosaurus lentus , Diplodocus longus , D. carnegii, Galeamopus and Dyslocosaurus polyonychius .
By the late Morrison, gigantic diplodocids (or similar species) had appeared, including Diplodocus hallorum (formerly Seismosaurus), Supersaurus vivianae , Amphicoelias altus , and M. fragilimus . Smaller sauropods, such as Suuwassea emiliae from Montana, tend to be found in the northern reaches of the Morrison, near the shores of the ancient Sundance Sea, suggesting ecological niches favoring smaller body size there compared with the giants found further south. [55]
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
H. delfsi [16] | Colorado, Brushy Basin member [16] | Partial skeleton lacking a skull. [56] | Small haplocanthosaurs of indeterminate classification, ranging about 14 m (46 ft) long. | ||
H. priscus [16] | Two skulless partial skeletons. [56] | ||||
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
M. fragillimus [16] | Colorado, Brushy Basin member [16] | A single, now lost, dorsal neural arch. [57] | Large rebbachisaurid. Based on a single lost neural arch 1.5 m (5 ft) tall. [57] | ||
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
D. polyonychius | Wyoming [58] | A fragmentary forelimb and partial hindlimbs. | Phylogenetic placement is uncertain. [58] | ||
Colorado, Brushy Basin member [16] | "Partial skull and cervicals." [60] | A dicraeosaurid sauropod. Originally described as "Morosaurus" agilis. [59] | |||
S. emilieae | Montana, Brushy Basin member [61] | A partial skull and some postcrania. [55] | A dicraeosaurid about 15m in length. | ||
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
A. altus [16] | Colorado, Brushy Basin member [16] | 2 dorsal vertebrae, femur, and a pubis. [62] | Large diplodocids about 25 m (82 ft) in length. [63] | ||
A. ajax [16] | — Colorado, Brushy Basin member [16] | A partial postcranial skeleton and posterior skull. [58] | Robust and abundantly widespread apatosaurine diplodocids reaching lengths of up to 25 m (82 ft). [64] "A." minimus likely belongs to a separate genus. | ||
A. louisae [14] | Four partial specimens, one of them including a skull. [58] Three of the specimens are from DNM, one is a mid cervical from Como Bluff. [58] | ||||
"A." minimus | Wyoming [9] | "Sacrum and pelvis." [60] | |||
A. viator | Howe-Stephens Quarry, Wyoming. | Holotype specimen MAB011899, a partial skeleton containing the sacrum, ribs, a coracoid and parts of the vertebral column and hindlegs. | A diplodocine sauropod from the younger layers of the Morrison Formation, originally considered a specimen of Diplodocus. [65] | ||
A. montanus | Colorado, Brushy Basin member [27] | A partial sacrum that cannot be distinguished from Camarasaurus or Apatosaurus. [66] | Dubious neosauropod. [66] | ||
B. excelsus | Two postcranial skeletons. [58] | Previously considered a species of Apatosaurus as per Riggs (1903). | |||
B. parvus | Utah and Wyoming, Salt Wash and Brushy Basin members | Three headless skeletons. [58] | Originally called Elosaurus. | ||
B. yahnahpin [58] | Wyoming, Brushy Basin member | A partial postcranial skeleton. [58] | An apatosaurine diplodocid slightly more primitive than Apatosaurus . Formerly placed in separate genus Eobrontosaurus. | ||
B. lentus [14] | 2 partial postcranial skeletons, with possibly more specimens assignable. [58] | A diplodocid about 24 m (79 ft) in length, similar in appearance to Diplodocus .It was the rarest sauropod in the Morrison Formation. [69] | |||
B. sp. | Wyoming, Utah and Oklahoma | ||||
D. carnegii [14] | Known from two skulls, five partial skeletons that lack skulls and manus, and hundreds of isolated postcranial remains. [71] | Large diplodocids reaching lengths of up to 28 m (92 ft). It was one of the most abundant sauropods in the area. [72] | |||
D. hallorum | New Mexico, Wyoming and Utah, Brushy Basin and Salt Wash members [51] | At least 4 partial postcranial skeletons [58] | Once classified as Seismosaurus . [73] [74] [75] [76] | ||
D. lacustris [16] | Colorado, Brushy Basin member [16] | Known from teeth and skull remains, the latter now referred to Camarasaurus . [58] Teeth cannot be referred beyond Flagellicaudata. [58] | |||
D. longus [14] | Colorado, Brushy Basin member [16] | Several caudal vertebrae. [77] | |||
G. hayi | Known from a partial skeleton and braincase. [71] | ||||
G. pabsti | Colorado and Wyoming, Brushy Basin member | A skull and partial postcranial skeleton, another individual known from partial skull. [58] | |||
K. siberi | Wyoming, Salt Wash member [78] | Skull and cervical vertebrae. [78] | |||
S. vivianae [16] | Colorado and Wyoming, Brushy Basin member | Known from several partial postcranial skeletons. [62] | A large diplodocid about 33–34 m 108–111 ft) in length | ||
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
B. altithorax [7] | Colorado, Brushy Basin and Salt Wash members [16] | Several partial skeletons and a partial skull. | A large brachiosaurid about 18–22 m (59–72 ft) long. | ||
C. annae [14] | Utah, Brushy Basin member [14] | A dorsal vertebra. | Camarasaurs reached an adult size of about 18 m (60 ft) in length. [79] C. annae junior synonym of C. lentus. C. lewisi was originally described as Cathetosarus lewisi and was later sunk into Camarasaurus, until being considered valid once again in 2013. | ||
C. grandis [16] | "At least 6 partial skeletons including 2 skulls, hundreds of postcranial elements." [56] | ||||
C. lentus [14] | "5 skeletons with skulls, hundreds of postcranial elements" [56] | ||||
Colorado, Brushy Basin member [16] | A nearly complete postcranial skeleton. [56] | ||||
C. supremus [16] | At least 4 partial skeletons including partial skulls. Many possible postcranial remains from Oklahoma. [81] | ||||
Indeterminate. | |||||
Dystrophaeus | D. viaemalae [83] | Utah, Tidwell member [83] | Multiple vertebrae, teeth and incomplete forelimb material. [83] | Previously recovered as a diplodocid, now recovered as a macronarian [83] Type material fragmentary, but recent rediscovery of type locality has discovered more material. [84] | |
Theropod dinosaurs, the carnivorous dinosaurs, came in several different types. The less derived types, the ceratosaurs and megalosaurids, included Ceratosaurus nasicornis , C. dentisulcatus, C. magnicornis, and the megalosaur Torvosaurus tanneri (including Edmarka rex ). Allosaurids included the common Allosaurus fragilis (including Epanterias amplexus ), A. jimmadseni, and the giant Saurophaganax maximus (potentially included in Allosaurus).
Indeterminate theropod remains have been recovered in Utah, with indeterminate ceratosaur remains formerly considered referable to Elaphrosaurus recovered in Colorado. Indeterminate theropod tracks have been recovered from both Utah and Arizona. [85]
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
A. fragilis [14] | Colorado, New Mexico, Oklahoma, South Dakota, Utah and Wyoming, Brushy Basin member [16] [51] [17] [68] [9] [86] | "At least [three] complete skulls, many partial skulls and skull elements, many partial and complete skeletons representing at least 60 individuals." [87] It was the most common large carnivore in the area. [88] [89] [90] | |||
A. jimmadseni [91] | Wyoming and Utah, Brushy Basin and Salt Wash members [86] [90] | At least 15 specimens, including several skulls. | |||
A. valens | Colorado [92] | Half of a proximal caudal centrum | |||
C. atrox | Wyoming, Brushy Basin member [94] | A fragmentary skull and assorted postcrania. [94] | Considered a junior synonym of Allosaurus. | ||
E. amplexus | Colorado, Brushy Basin member [95] | Several fragmentary postcranial elements of 2 individuals, [96] possible additional remains known from Wyoming. [97] | |||
L. lucaris | Wyoming, Brushy Basin member [92] | A fragmentary skull and several postcranial elements. [93] [92] | Junior synonym of A. fragilis. [92] | ||
L. ferox | Wyoming, Brushy Basin member [92] | A partial skull, dentaries, and fragmentary postcrania. [98] [92] | Known from one specimen with several pathologies. Today considered a junior synonym of A. fragilis. [92] | ||
S. maximus [17] | Several partial postcranial skeletons and fragmentary skull material. [92] [99] [86] | Generally considered to be its own genus. Sometimes considered to be a species of Allosaurus. [100] [101] |
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
C. dentisulcatus [14] | Utah [14] | "Partial skull, vertebrae, [and] limb elements." [102] | Large ceratosaurs grew to lengths of about 6–7 meters (20–23 ft.) in length with large nasal horns on their snouts as well as two smaller horns above the eyes. | ||
C. magnicornis [16] | Colorado [16] | "Skull [and] assorted postcrania." [102] | |||
C. nasicornis [16] | Remains of "5 individuals, including [a] nearly complete adult skeleton and subadult skeleton." [102] | ||||
Indeterminate. [9] | Wyoming [9] | ||||
Indeterminate. [16] | Colorado [16] | Previously referred to Elaphrosaurus , [103] [104] [105] these remains are probably not referable to that genus and are best considered indeterminate beyond Ceratosauria. [106] | |||
Intermediate [16] | Colorado [16] | Now thought to be indeterminate beyond Ceratosauria. | |||
F. churei [107] | Wyoming [107] | Tibia, astragalus, fibula. [107] | A fragmentary theropod which may be a ceratosaurid. | ||
Coelurosaurs, the group of theropods most closely related to and including birds, included Coelurus fragilis , Ornitholestes hermanni , Tanycolagreus topwilsoni , the possible troodontid Koparion douglassi , the definite troodontid Hesperornithoides , and the early tyrannosauroid Stokesosaurus clevelandi .
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
C. fragilis [14] | A partial skeleton in several syntypes and several fragmentary referred specimens. [108] | A basal coelurosaurian about 2.3 m (7.5 ft) long. | |||
Indeterminate. [16] | Colorado [16] | ||||
H. miessleri | Wyoming | An early troodontid. | |||
K. douglassi [14] | Utah [14] | A small theropod thought to be one of the oldest known troodontids. | |||
P. thomsoni [16] | Colorado, Brushy Basin member [16] | A distal radius | |||
O. hermanni [9] | Wyoming [9] | "Skull and associated postcranial skeleton." [108] | A small basal coelurosaurian about 2 m (6.5 ft) long. | ||
S. clevelandi [14] | Utah [14] | "Illium, associated elements and pelvic cranial material. [sic]" [110] | A possible early tyrannosauroid about 4 m (13 ft) in length. | ||
T. topwilsoni | Wyoming and Utah | A basal coelurosaurian about 3.4 m (11.3 ft) long, similar in appearance to Coelurus . | |||
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
E. rex [9] |
| Possibly a junior synonym of Torvosaurus tanneri. | |||
M. bicentesimus [14] | Partial skeleton, including part of a skull. [111] | A medium-sized piatnitzkysaurid megalosauroid about 6 m (20 ft) in length. | |||
T. tanneri [14] | Colorado, Utah and Wyoming, Brushy Basin member [16] [14] [9] | "Partial skeletons of at least [three] individuals." [112] | A large, robust megalosaurid reaching lengths of up to 9 m (30 ft). [113] One of the largest carnivores of the formation. | ||
Dinosaur eggs have been found in Utah. [14]
Morrison ornithopod trace fossils are represented by three toed tracks which are generally small. [6] The toes of Morrison ornithopod tracks are usually more widely splayed than the theropod tracks preserved in the formation. [6]
Stegosaur tracks were first recognized in 1996 from a hindprint-only trackway discovered at the Cleveland-Lloyd quarry, which is located near Price, Utah. [42] Two years later, a new ichnogenus called Stegopodus was erected for another set of stegosaur tracks which were found near Arches National Park, also in Utah. [42] Unlike the first, this trackway preserved traces of the forefeet. Fossil remains indicate that stegosaurs have five digits on the forefeet and three weight-bearing digits on the hind feet. [42] From this, scientists were able to successfully predict the appearance of stegosaur tracks in 1990, six years in advance of the first actual discovery of Morrison stegosaur tracks. [42] Since the erection of Stegopodus, more trackways have been found, however none have preserved traces of the front feet, and stegosaur traces remain rare. [42]
Indeterminate theropod tracks have been recovered from both Utah and Arizona. [85]
Allosaurus is an extinct genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period. The name "Allosaurus" means "different lizard", alluding to its unique concave vertebrae. It is derived from the Greek words ἄλλος and σαῦρος. The first fossil remains that could definitively be ascribed to this genus were described in 1877 by famed paleontologist Othniel Charles Marsh. The genus has a very complicated taxonomy and includes at least three valid species, the best known of which is A. fragilis. The bulk of Allosaurus remains have come from North America's Morrison Formation, with material also known from the Lourinhã Formation in Portugal. It was known for over half of the 20th century as Antrodemus, but a study of the abundant remains from the Cleveland-Lloyd Dinosaur Quarry returned the name "Allosaurus" to prominence. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles.
Stegosaurus is a genus of herbivorous, four-legged, armored dinosaur from the Late Jurassic, characterized by the distinctive kite-shaped upright plates along their backs and spikes on their tails. Fossils of the genus have been found in the western United States and in Portugal, where they are found in Kimmeridgian- to Tithonian-aged strata, dating to between 155 and 145 million years ago. Of the species that have been classified in the upper Morrison Formation of the western US, only three are universally recognized: S. stenops, S. ungulatus and S. sulcatus. The remains of over 80 individual animals of this genus have been found. Stegosaurus would have lived alongside dinosaurs such as Apatosaurus, Diplodocus, Camarasaurus and Allosaurus, the latter of which may have preyed on it.
Ceratosaurus was a carnivorous theropod dinosaur that lived in the Late Jurassic period. The genus was first described in 1884 by American paleontologist Othniel Charles Marsh based on a nearly complete skeleton discovered in Garden Park, Colorado, in rocks belonging to the Morrison Formation. The type species is Ceratosaurus nasicornis.
Torvosaurus is a genus of large megalosaurine theropod dinosaur that lived approximately 165 to 148 million years ago during the Callovian to Tithonian ages of the late Middle and Late Jurassic period in what is now Colorado, Portugal, Germany, and possibly England, Spain, Tanzania, and Uruguay. It contains two currently recognized species, Torvosaurus tanneri and Torvosaurus gurneyi, plus a third unnamed species from Germany.
Dryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont. Fossils have been found in the western United States and were first discovered in the late 19th century. Valdosaurus canaliculatus and Dysalotosaurus lettowvorbecki were both formerly considered to represent species of Dryosaurus.
Camptosaurus is a genus of plant-eating, beaked ornithischian dinosaurs of the Late Jurassic period of western North America and possibly also Europe. The name means 'flexible lizard'.
Como Bluff is a long ridge extending east–west, located between the towns of Rock River and Medicine Bow, Wyoming. The ridge is an anticline, formed as a result of compressional geological folding. Three geological formations, the Sundance, the Morrison, and the Cloverly Formations, containing fossil remains from the Late Jurassic of the Mesozoic Era are exposed.
Coelurus is a genus of coelurosaurian dinosaur from the Late Jurassic period. The name means "hollow tail", referring to its hollow tail vertebrae. Although its name is linked to one of the main divisions of theropods (Coelurosauria), it has historically been poorly understood, and sometimes confused with its better-known contemporary Ornitholestes. Like many dinosaurs studied in the early years of paleontology, it has had a confusing taxonomic history, with several species being named and later transferred to other genera or abandoned. Only one species is currently recognized as valid: the type species, C. fragilis, described by Othniel Charles Marsh in 1879. It is known from one partial skeleton found in the Morrison Formation of Wyoming, United States. It was a small bipedal carnivore with elongate legs.
Elaphrosaurus is a genus of ceratosaurian theropod dinosaur that lived approximately 154 to 150 million years ago during the Late Jurassic Period in what is now Tanzania in Africa. Elaphrosaurus was a medium-sized but lightly built member of the group that could grow up to 6.2 m (20 ft) long. Morphologically, this dinosaur is significant in two ways. Firstly, it has a relatively long body but is very shallow-chested for a theropod of its size. Secondly, it has very short hindlimbs in comparison with its body. Phylogenetic analyses indicate that this genus is likely a ceratosaur. Earlier suggestions that it is a late surviving coelophysoid have been examined but generally dismissed. Elaphrosaurus is currently believed to be a very close relative of Limusaurus, an unusual beaked ceratosaurian which may have been either herbivorous or omnivorous.
Saurophaganax is a genus of large allosauroid dinosaur from the Morrison Formation of Late Jurassic Oklahoma, United States. Some paleontologists consider it to be a junior synonym and species of Allosaurus. Saurophaganax represents a very large Morrison allosauroid characterized by horizontal laminae at the bases of the dorsal neural spines above the transverse processes, and "meat-chopper" chevrons. It was the largest terrestrial carnivore of North America during the Late Jurassic, reaching 10.5 metres (34 ft) in length and 2.7–3.8 metric tons in body mass.
Stokesosaurus is a genus of small, carnivorous early tyrannosauroid theropod dinosaurs from the late Jurassic period of Utah, United States and Guimarota, Portugal.
Dracopelta is a monospecific genus of ankylosaur dinosaur from Portugal that lived during the Late Jurassic in what is now the Lourinhã Formation. The type and only species is Dracopelta zbyszewskii, which is represented by a partial skeleton including unpublished material.
Nanosaurus is an extinct genus of neornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic in North America. Its fossils are known from the Morrison Formation of the south-western United States. The type and only species, Nanosaurus agilis, was described and named by Othniel Charles Marsh in 1877. The taxon has a complicated taxonomic history, largely the work of Marsh and Peter M. Galton, involving the genera Laosaurus, Hallopus, Drinker, Othnielia, and Othnielosaurus, the latter three now being considered to be synonyms of Nanosaurus. It had historically been classified as a hypsilophodont or fabrosaur, types of generalized small bipedal herbivore, but more recent research has abandoned these groupings as paraphyletic and Nanosaurus is today considered a basal member of Neornithischia.
Phyllodon was a genus of small ornithischian dinosaur from the Kimmeridgian-aged Upper Jurassic Camadas de Guimarota Formation of Leiria, Portugal and possibly also the Bathonian-aged Chipping Norton Limestone of England. It may have been closely related to contemporaneous dinosaurs in North America.
Dinheirosaurus is a genus of diplodocid sauropod dinosaur that is known from fossils uncovered in modern-day Portugal. It may represent a species of Supersaurus. The only species is Dinheirosaurus lourinhanensis, first described by José Bonaparte and Octávio Mateus in 1999 for vertebrae and some other material from the Lourinhã Formation. Although the precise age of the formation is not known, it can be dated around the early Tithonian of the Late Jurassic.
Marshosaurus is a genus of medium-sized carnivorous theropod dinosaur, belonging to the family Piatnitzkysauridae, from the Late Jurassic Morrison Formation of Utah and possibly Colorado.
Uteodon is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the late Jurassic period in what is now Uintah County, Utah. It is known from the middle of the Brushy Basin Member, Morrison Formation. The genus was named by Andrew T. McDonald in 2011 and the type species is U. aphanoecetes.
Alcovasaurus, alternatively known as Miragaia longispinus, is a genus of herbivorous stegosaurian dinosaur that lived in the Late Jurassic. It was found in the Morrison Formation of Natrona County, Wyoming, United States. The type species is Stegosaurus longispinus, later given the genus Alcovasaurus.
Ardetosaurus is an extinct genus of diplodocid sauropod dinosaurs from the Late Jurassic (Kimmeridgian) Morrison Formation of northern Wyoming, United States. The genus contains a single species, Ardetosaurus viator. It was first described in 2024 on the basis of a partial articulated skeleton, including vertebrae from the neck, back, and tail, hip bones, and part of the left hindlimb. The genus is a member of the Diplodocinae, a subfamily of large long-necked dinosaurs with whiplike tails. Ardetosaurus represents one of many distinct sauropod taxa that coexisted in this formation.