List of dinosaurs of the Morrison Formation


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.

Fauna comparisons

The fauna of Morrison Formation is similar to one in the coeval rocks of Tendaguru Beds and Lourinhã Formation in Portugal, mostly with the second. Some genera are shared in Morrison and Lourinhã, such as Torvosaurus, Ceratosaurus, Stegosaurus, Dryosaurus, and Allosaurus.
In sum, Morrison Fm has 37 valid genera of dinosaurs.

Ornithischians

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 armatus, S. 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. Larger but similar-looking dryosaurids were represented by Dryosaurus altus 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.

Neornithischians

GenusSpeciesStateMemberMaterialNotesImages

Anomoepus
  • CO
Morrison Anomoepus lack the handprint impressions found associated with earlier instances of the ichnogenus in New England.



Camptosaurus
C. amplus
  • WY
Now known to be based on a theropod foot.



Camptosaurus
C. aphanoecetes
  • UT
  • Brushy Basin
    		• Reclassified as Uteodon.



    Camptosaurus
    C. browni
    Junior synonym of C. dispar.



    Camptosaurus
    C. dispar
    • CO
    • OK
    • UT
    • WY
    		" disarticulated skull elements, some with associated postcrania, approximately partial, articulated skeletons, juvenile to adult."
    A member of Camptosauridae. Junior synonyms include Camptosaurus browni, C. medius, and C. nanus.



    Camptosaurus
    C. medius
    Junior synonym of C. dispar.



    Camptosaurus
    C. nanus
    Junior synonym of C. dispar.



    Dinehichnus
    • UT
  • Saltwash
    		• 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.
    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".



    Drinker
    D. nisti
    • WY
    		"Partial skull and postcranial skeleton."
    A basal neornithischian about 2 m long, slightly smaller than Othnielosaurus. Junior synonym of Nanosaurus agilis



    Dryosaurus
    D. altus
    • CO
    • WY
  • Brushy Basin
    		• The remains of many individuals have been uncovered, with some sites containing hundreds of bones from Dryosaurus of multiple age groups.
    A large dryosaurid iguanodont up to 2.4 m long and 114 kg in weight. It was physically similar to Othnielosaurus, although larger and with more derived teeth.



    Dryosaurus
    D. elderae
    • UT
  • Brushy Basin
    		• A large dryosaurid iguanodont up to 2.4 m long and 114 kg in weight. It was physically similar to Othnielosaurus, although larger and with more derived teeth.



    "Laosaurus"
    L. altus
    Now known as Dryosaurus altus



    "Laosaurus"
    L. celer
    • WY
    		Considered dubious due to fragmentary remains.



    "Laosaurus"
    L. consors
    Now known as Othnielosaurus consors



    "Laosaurus"
    "L. gracilis"
    Considered dubious due to fragmentary remains.



    Nanosaurus
    N. agilis
    • CO
    		A small ornithopod, possibly a hypsilophodont



    Othnielia
    O. rex
    • CO
    		Based on an isolated femur
    A small neornithischian 2 m in length. Dubious; many remains historically assigned to this taxon are now place within Othnielosaurus.



    Othnielosaurus
    O. consors
    • UT
    • WY
    		A basal neornithischian about 2 m long. Junior synonym of Nanosaurus agilis



    Preprismatoolithus
    P. coloradensis
    • CO
  • Salt Wash
    		• Eggshell present in great abundance at the so-called "Young Egg Locality" which seems to have been a dinosaur nesting ground. Congeneric eggshell fossils are found at additional Colorado sites including the Fruita Paleontological Area, the Uravan Locality and Garden Park.
    P. coloradensis is described by John Foster as being "of the prismatic basic type," with subspherical eggs about 10 cm in diameter. This oospecies has been attributed to "hypsilophodontid" dinosaurs, although a lack of associated embryo material currently makes confirming the egg-layer's identity impossible.



    Tichosteus
    T. aequifacies
    • CO
    		"Vertebrae."



    Tichosteus
    T. lucasanus
    • CO
    		"Vertebra."



    Uteodon
    U. aphanoecetes
    • UT
  • Brushy Basin


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    Thyreophorans

    GenusSpeciesStateMemberMaterialNotesImages

    Anomoepus



    Gargoyleosaurus
    G. parkpinorum
    • WY
    		"Skull partial postcranium."
    A polacanthine nodosaur known from reasonably complete fossil remains. Its skull measures 29 centimeters in length, and its total body length is an estimated 3 to 4 meters. It may have weighed as much as 1 tonne.



    Hesperosaurus
    H. mjosi
    • WY
    		"Complete skeleton with skull, subadult." Known only from a single specimen.
    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



    Miragaia
    M. longispinus
    • WY
    		"Fragmentary postcranial skeleton, adult."
    A dacentrurinae stegosaurid physically similar to Stegosaurus stenops but with much larger tail spines. It is also similar to Kentrosaurus in having long dermal spikes on the caudal region. 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. On 2019 the genus Alcovasaurus was considered a junior synonym of Miragaia



    Mymoorapelta
    M. maysi
    • CO
  • Brushy Basin
    		• "Skull fragments, portions of skeletons, other postcrania."
    Both the first ankylosaur discovered in the formation and the first known North American Jurassic ankylosaur. It probably weighed 500 kg in life.



    Stegopodus
    • UT
    		Stegopodus represent only a portion of the Morrison's stegosaur tracks, which are already rare and generally only preserve the animal's hind feet.
    Stegosaur tracks which record front feet with five digits and hind feet with three weight-bearing digits. The general morphology of the tracks fit scientific predictions made eight years in advance of the erection of Stegopodus.



    Stegosaurus
    S. armatus
    • CO
    • UT
    • WY
    		" partial skeletons, braincases, at least fragmentary postcrania, adult."
    S. armatus is both the first Stegosaurus to be discovered and the type species. Its type specimen is poorly preserved, incomplete, and has never been fully prepared. Consequently it is not possible to tell which, if any, of the subsequently erected Stegosaurus species are synonymous with it, and it is likely one or more of them are. Sometimes considered dubious.



    Stegosaurus
    S. stenops
    • CO
    • UT
    • WY
    		" complete skeletons with skulls, braincases, at least partial postcrania, juvenile to adult."
    The best known Stegosaurus species, it has shorter limbs and larger plates than S. ungulatus.



    Stegosaurus
    S. sulcatus
    • WY
    		Often considered synonymous with S. armatus, it may be distinct. Potentially has a shoulder spike, otherwise unknown in Stegosaurus, despite presence in relatives.



    Stegosaurus
    S. ungulatus
    • UT
    • WY
    		S. ungulatus had longer limbs and comparatively smaller plates than the better known S. stenops. Although formerly portrayed with eight tail spikes, it is now known to have had the typical four. Possibly synonymous with S. armatus. Sometimes considered dubious.



    Stegosaurus
    Indeterminate.
    • NM
    • OK



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    Misc

    GenusSpeciesStateMemberMaterialNotesImages

    Anomoepus

    Fruitadens
    F. haagarorum
    • CO
  • Brushy Basin
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    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 and Haplocanthosaurus. Sauropods including Haplocanthosaurus priscus, H. delfsi, and the diplodocid Eobrontosaurus 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, 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 had appeared, including Diplodocus hallorum, 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.

    Haplocanthosaurids

    GenusSpeciesStateMemberMaterialNotesImages

    Haplocanthosaurus
    H. delfsi
    • CO
    		Partial skeleton lacking a skull.
    Small haplocanthosaurs of indeterminate classification, ranging about 14 m long.

    Haplocanthosaurus
    H. priscus
    • CO
    • WY
    		Two skulless partial skeletons.
    Small haplocanthosaurs of indeterminate classification, ranging about 14 m long.

    Rebbachisaurids

    GenusSpeciesStateMemberMaterialNotesImages

    Maraapunisaurus
    M. fragillimus
    • CO
    		"Single neural arch."
    Large rebbachisaurid. Based on a single lost neural arch 1.5 m tall.    		''

    Dicraeosaurids

    GenusSpeciesStateMemberMaterialNotesImages

    Dyslocosaurus
    D. polyonychius
    WY

    Suuwassea
    S. emilieae
    MT
    A dicraeosaurid about 15m in length.

    Diplodocids

    GenusSpeciesStateMemberMaterialNotesImages

    Amphicoelias
    A. altus
    • CO
    		"Dorsal vertebrae, pubis, femur."
    Large diplodocids about 25 m in length.









    Apatosaurus
    A. ajax
    • CO
    		Two partial skeletons and a braincase.
    Robust apatosaurine diplodocids reaching lengths of up to 25 m. "A." minimus likely belongs to a separate genus.









    Apatosaurus
    A. louisae
    • CO
    • UT
    • WY
    		Two mostly complete skeletons, but only one preserving a skull. An additional partial skeleton and isolated limb elements have been found.
    Robust apatosaurine diplodocids reaching lengths of up to 25 m. "A." minimus likely belongs to a separate genus.









    Apatosaurus
    "A." minimus
    • WY
    		"Sacrum and pelvis."
    Robust apatosaurine diplodocids reaching lengths of up to 25 m. "A." minimus likely belongs to a separate genus.









    Atlantosaurus
    A. montanus
    Dubious diplodocid.









    Brontosaurus
    B. excelsus
    • WY
    		Two postcranial skeletons.
    Previously considered a species of Apatosaurus as per Riggs.









    Brontosaurus
    B. parvus
    • UT
    • WY
    		Three headless skeletons.
    Originally called Elosaurus.









    Brontosaurus
    B. yahnahpin    		* WY
    An apatosaurine diplodocid slightly more primitive than Apatosaurus. Formerly placed in separate genus Eobrontosaurus.









    Barosaurus
    B. lentus
    • SD
    • UT
    		" partial skeletons without skulls isolated limb elements."
    A diplodocid about 24 m in length, similar in appearance to Diplodocus.









    Barosaurus
    B. sp.
    • WY
    • UT
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    Diplodocus
    D. carnegii
    • WY
    		Known from two skulls, five partial skeletons that lack skulls and manus, and hundreds of isolated postcranial remains.
    Large diplodocids reaching lengths of up to 28 m.









    Diplodocus
    D. hallorum
    • NM
    • WY
    • UT
    		"Pelvis partial vertebral column."
    Once classified as Seismosaurus.









    Diplodocus
    D. lacustris
    • CO
    		Known from a dentary with teeth. Dubious.-









    Diplodocus
    D. longus
    • CO
    		Known from two skulls and a series of tail vertebrae.-









    Galeamopus
    G. hayi
    • WY
    		Known from a partial skeleton and braincase.-









    Galeamopus
    G. pabsti
    • CO
    • WY
    		Based on skulls previously assigned to Diplodocus.-









    Kaatedocus
    K. siberi
    • WY
    		Skull and cervical vertebrae.-









    Parabrontopodus









    "Morosaurus"
    M. agilis
    • CO
    		"Partial skull and cervicals."
    A diplodocine diplodocid.









    Supersaurus
    S. vivianae
    • CO
    • WY
    		Known from some neck vertebrae, shoulder elements, and ischium and some proximal tail vertebrae.
    A large diplodocid about 33–34 m 108–111 ft) in length








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    Macronarians

    GenusSpeciesStateMemberMaterialNotesImages

    Brachiosaurus
    B. altithorax
    • CO
    		Partial skeleton.
    A large brachiosaurid about 26 m long.


    Brontopodus


    Camarasaurus
    C. annae
    • UT
    		Camarasaurs reached an adult size of about 18 m in length. A Camarasaurus pelvis from the Cleveland-Lloyd Quarry shows evidence of gouging that has been attributed to Allosaurus. A juvenile specimen was recovered from Dinosaur National Monument in Utah. C. annae junior synonym of C. lentus. C. lewisi was originally described as Cathetosarus lewisi, but was later sunk into Camarasaurus. Recent research indicates it is indeed distinct.


    Camarasaurus
    C. grandis
    • CO
    • MT
    • WY
    		"At least 6 partial skeletons including 2 skulls, hundreds of postcranial elements."
    Camarasaurs reached an adult size of about 18 m in length. A Camarasaurus pelvis from the Cleveland-Lloyd Quarry shows evidence of gouging that has been attributed to Allosaurus. A juvenile specimen was recovered from Dinosaur National Monument in Utah. C. annae junior synonym of C. lentus. C. lewisi was originally described as Cathetosarus lewisi, but was later sunk into Camarasaurus. Recent research indicates it is indeed distinct.


    Camarasaurus
    C. lentus
    • UT
    • WY
    		"5 skeletons with skulls, hundreds of postcranial elements"
    Camarasaurs reached an adult size of about 18 m in length. A Camarasaurus pelvis from the Cleveland-Lloyd Quarry shows evidence of gouging that has been attributed to Allosaurus. A juvenile specimen was recovered from Dinosaur National Monument in Utah. C. annae junior synonym of C. lentus. C. lewisi was originally described as Cathetosarus lewisi, but was later sunk into Camarasaurus. Recent research indicates it is indeed distinct.


    Camarasaurus
    C. lewisi
    • CO
    		"Nearly complete postcranial skeleton."
    Camarasaurs reached an adult size of about 18 m in length. A Camarasaurus pelvis from the Cleveland-Lloyd Quarry shows evidence of gouging that has been attributed to Allosaurus. A juvenile specimen was recovered from Dinosaur National Monument in Utah. C. annae junior synonym of C. lentus. C. lewisi was originally described as Cathetosarus lewisi, but was later sunk into Camarasaurus. Recent research indicates it is indeed distinct.


    Camarasaurus
    C. supremus
    • CO
    • NM
    • WY
    		"At least 5 partial skeletons including braincase and jaws."
    Camarasaurs reached an adult size of about 18 m in length. A Camarasaurus pelvis from the Cleveland-Lloyd Quarry shows evidence of gouging that has been attributed to Allosaurus. A juvenile specimen was recovered from Dinosaur National Monument in Utah. C. annae junior synonym of C. lentus. C. lewisi was originally described as Cathetosarus lewisi, but was later sunk into Camarasaurus. Recent research indicates it is indeed distinct.


    Camarasaurus
    Indeterminate.
    • OK
    • SD
    • TX
    		Camarasaurs reached an adult size of about 18 m in length. A Camarasaurus pelvis from the Cleveland-Lloyd Quarry shows evidence of gouging that has been attributed to Allosaurus. A juvenile specimen was recovered from Dinosaur National Monument in Utah. C. annae junior synonym of C. lentus. C. lewisi was originally described as Cathetosarus lewisi, but was later sunk into Camarasaurus. Recent research indicates it is indeed distinct.


    Cathetosaurus
    C. lewisi
    • CO
    		"Nearly complete postcranial skeleton."
    Formerly considered a junior synonym of Camarasaurus; apparently a genus distinct from Camarasaurus.

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    Theropods

    s, the carnivorous dinosaurs, came in several different types. The less derived types, the ceratosaurs and megalosaurids, included Ceratosaurus nasicornis, C. dentisulcatus, C. magnicornis, Elaphrosaurus sp., and the megalosaur Torvosaurus tanneri. Allosaurids included the common Allosaurus fragilis, Allosaurus new species, A. lucasi, and giant Saurophaganax maximus. Also a recently discovered dinosaur has turned out to be a new species, not Allosaurus.
    Indeterminate theropod remains have been recovered in Utah. Indeterminate theropod tracks have been recovered from both Utah and Arizona.

    Carnosaurs

    GenusSpeciesStateMemberMaterialNotesImages

    Allosaurus
    A. fragilis
    • CO
    • NM
    • OK
    • SD
    • UT
    • WY
  • Brushy Basin
    		• "At least complete skulls, many partial skulls and skull elements, many partial and complete skeletons representing at least 60 individuals."

    Allosaurus
    A. jimmadseni
    • CO
    • WY
    • UT
  • Salt Wash

    • Allosaurus
    A. lucasi
    • CO

    Antrodemus
    A. valens
    Considered dubious due to fragmentary remains.

    Creosaurus
    C. atrox
    Considered a junior synonym of Allosaurus.

    Epanterias
    E. amplexus
    Considered dubious due to fragmentary remains.

    Labrosaurus
    L. lucaris
    Junior synonym of A. fragilis.

    Labrosaurus
    L. ferox
    Known from one specimen with several pathologies. Today considered a junior synonym of A. fragilis.

    Saurophaganax
    S. maximus
    • OK
    		"Isolated cranial and postcranial elements."
    Generally considered to be its own genus. Sometimes considered to be a species of Allosaurus.

    Ceratosaurs

    GenusSpeciesStateMemberMaterialNotesImages

    Ceratosaurus
    C. dentisulcatus
    • UT
    		"Partial skull, vertebrae, limb elements."
    Large ceratosaurs grew to lengths of about 6–7 meters in length with large nasal horns on their snouts as well as two smaller horns above the eyes.


    Ceratosaurus
    C. magnicornis
    • CO
    		"Skull assorted postcrania."
    Large ceratosaurs grew to lengths of about 6–7 meters in length with large nasal horns on their snouts as well as two smaller horns above the eyes.


    Ceratosaurus
    C. nasicornis
    • CO
    • UT
    		Remains of "5 individuals, including nearly complete adult skeleton and subadult skeleton."
    Large ceratosaurs grew to lengths of about 6–7 meters in length with large nasal horns on their snouts as well as two smaller horns above the eyes.


    Ceratosaurus
    Indeterminate.
    • WY
    		Large ceratosaurs grew to lengths of about 6–7 meters in length with large nasal horns on their snouts as well as two smaller horns above the eyes.


    Ceratosauria
    Indeterminate.
    • CO
    		Previously referred to Elaphrosaurus, these remains are probably not referable to that genus and are best considered indeterminate beyond Ceratosauria.


    Elaphrosaurus
    Intermediate
    • CO
    		Now thought to be intermediate beyond Ceratosauria.


    Fosterovenator
    F. churei
    • WY
    		Tibia, astragalus, fibula.
    A fragmentary theropod which may be a ceratosaurid.

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    Coelurosaurs

    , more derived types more closely related to birds, included Coelurus fragilis, Ornitholestes hermanni, Tanycolagreus topwilsoni, the possible troodontid Koparion douglassi, the definite troodontid Hesperornithoides, and the early tyrannosauroid Stokesosaurus clevelandi.
    GenusSpeciesStateMemberMaterialNotesImages

    Coelurus
    C. fragilis
    • UT
    • WY
    		"Postcranial skeleton."
    A basal coelurosaurian about 2.3 m long.






    Coelurus
    Indeterminate.
    • CO
    		A basal coelurosaurian about 2.3 m long.






    Hesperornithoides
    H. miessleri
    • WY
    		An early troodontid.






    Koparion
    K. douglassi
    • UT
    		A small theropod thought to be one of the oldest known troodontids.






    Palaeopteryx
    P. thomsoni
    • CO






    Ornitholestes
    O. hermanni
    • UT
    • WY
    		"Skull and associated postcranial skeleton."
    A small basal coelurosaurian about 2 m long.






    Stokesosaurus
    S. clevelandi
    • UT
    		"Illium, associated elements and pelvic cranial material. "
    A possible early tyrannosauroid about 4 m in length.






    Tanycolagreus
    T. topwilsoni
    • UT
    		A basal coelurosaurian about 3.4 m long, similar in appearance to Coelurus.





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    Megalosauroids

    GenusSpeciesStateMemberMaterialNotesImages

    Edmarka
    E. rex
    • WY
    		Junior synonym of Torvosaurus tanneri.-

    Marshosaurus
    M. bicentesimus
    • CO
    • UT
    		Partial skeleton, including part of a skull.
    A medium-sized piatnitzkysaurid megalosauroid about 6 m in length.

    Torvosaurus
    T. tanneri
    • CO
    • UT
    • WY
  • Brushy Basin
    		• "Partial skeletons of at least individuals."
    A large, robust megalosaurid reaching lengths of up to 11 m. One of the largest carnivores of the formation.
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    Eggs

    Dinosaur eggs have been found in Utah.

    Tracks

    Ornithopods

    Morrison ornithopod trace fossils are represented by three toed tracks which are generally small. The toes of Morrison ornithopod tracks are usually more widely splayed than the theropod tracks preserved in the formation.

    Stegosaurs

    Stegosaur tracks were first recognized in 1996 from a hindprint-only trackway discovered at the Clevland-Lloyd quarry, which is located near Price, Utah. 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. 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. 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. Since the erection of Stegopodus, more trackways have been found, however none have preserved traces of the front feet, and stegosaur traces remain rare.

    Theropods

    Indeterminate theropod tracks have been recovered from both Utah and Arizona.

    Footnotes