Paleobiota of the Morrison Formation

The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has a wide assortment of taxa represented in its fossil record, including 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 distinctive banding of the Morrison Formation, a group of rock layers that occur throughout Dinosaur National Monument and the source of fossils like those found at the Dinosaur Quarry.

(mostly from Foster [2003]; the higher-level classifications will vary as new finds are made.

Plants

Gnetales
Genus Species Locality Material Notes

Bassitheca[1]

B. hoodiorum

Colorado and Utah (Brushy Basin Member)

More than 300 specimens, three dimensional calcitic casts of a two-seeded compound cone

Tentatively assigned as a gnetale, with some attributes of the cones pointing towards a close relation with the extant genus Ephedra.

Dayvaultia[2]

D. tetragona

Henry Mountains of Utah (Brushy Basin Member)

"Three-dimensional casts and partially permineralized small cones".

A gnetale with close affinities to Cretaceous and modern genera.

Invertebrates

Arthropods
Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Name Species Locality Material Notes

Eopolis

E. ekdalei

Utah, Brushy Basin member

Nests produced by social insects.[3]
Morrisonnepa[4] M. jurassica

Utah

 A hemipteran belonging to the group Nepomorpha.
Parapleurites[5] P. morrisonensis

Colorado

 a forewing. A Locustopsid orthopteran

Tektonargus

T. kollaspilus

Colorado, Brushy Basin member

Five specimens were reported in the original description of the ichnogenus.

Vertebrates

Fish

Although the paleoclimate of the Morrison formation was semiarid with only seasonal rainfall, there were enough bodies of water to support a diverse ichthyofauna.[6] Although abundant, fish remains are constrained to only certain locations within the formation.[6] Microvertebrate sites in Wyoming are dominated by fish remains.[6] Indeterminate ray-finned fish remains have been recovered from Ninemile Hill and a microvertebrate site in the Black Hills.[6] Found in stratigraphic zones 2, 4, and 5.[7] Morrison actinopterygians generally have no close modern relatives.[6] The Wyoming microvertebrate remains are extracted from the sediment by screenwashing.[6] Paleoniscoid remains are geographically present in the western part of Colorado, where remains have been recovered from "a level above the Mygatt-Moore Quarry."[6] Largely complete remains of small individuals have been consistently recovered for over 15 years.[6] Single tooth fossil of pycnodont fish is represented from Dinosaur National Monument in Utah,[8] found in stratigraphic zone 4.[7] Dipnoan remains found at a fossil site not far from Cañon City, Colorado.[6] Remains usually in a state of rather complete preservation.[6] Halecostome remains are geographically present in the western part of Colorado, where remains have been recovered from "a level above the Mygatt-Moore Quarry."[6] Largely complete remains of small individuals have been consistently recovered for over 15 years.[6] Amiid remains found in stratigraphic zones 2, 3, and 4.[7] Found at a fossil site not far from Cañon City, Colorado.[6] Remains usually in a state of rather complete preservation.[6]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Name Species Locality Material Notes Images

Ceratodus[9]

C. fossanovum[6]

A lungfish genus whose members ranged from 1 to 2 m in length and weights of up to 79 pounds, with most Morrison lungfish being on the smaller end of that range.[6] These species are believed to have had similar diets to extant lungfish like the physically similar modern genus Neoceratodus.[6]
Ceratodus.
Leptolepis.

C. ?frazieri[6]

C. guentheri[6]

C. robustus[6]

Indeterminate.

Brushy Basin and Saltwash members

Represented by tooth plates.

Hulettia[9]

H. hawesi[10]

Colorado

A small fish of the division Halecostomi about 7.6 cm in length and 5g of live mass which probably preferred quiet water. Its fossils prominently preserve its thick interlocking scales.

cf. Leptolepis[9]

N/A

Colorado[10]

Known only from a single nearly complete skeleton found at Rabbit Valley.[11] Found in stratigraphic zone 5.[7]

A 13 cm (5 inch) fish that was deeper bodied than its co-occurring contemporaries Morrolepis and Hulettia.[11] The Morrison cf. Leptolepis probably had a live mass of about 37g.[11] It is the only teleost fish known from the formation and was morphologically more highly derived than other Morrison fish.[11] It is believed to have fed on contemporary fish and small invertebrates.[11]

Morrolepis[9]

M. schaefferi[12]

Colorado

A coccolepidid "palaeoniscoid" with forward-set eyes positioned past the front end of the lower jaw. It had a tall dorsal fin set far back on the body and an asymmetrical caudal fin.[12] Adult specimens would reach about 20 cm in length and 113 g (4 oz) in mass.[12]

Potamoceratodus

P. guentheri

Colorado

Once thought to be a species of Ceratodus.

Amphibians
A modern frog from the same family as Rhadinosteus parvus, the rhinophrynidae.

Frogs are known from several sites in the Morrison Formation, but are not particularly well represented.[13] The history of Morrison anuran discoveries began with the recovery of remains from Quarry 9 near Como Bluff, Wyoming. The new genus Eobatrachus was erected for some of these remains by O. C. Marsh, but the material was later considered non-diagnostic. Decades later another dubious anuran genus, Comobatrachus, was erected based on additional fragmentary remains. Despite the erection of multiple new names, only two frog species are currently recognised from the Morrison: Enneabatrachus hechti[14] and Rhadinosteus parvus.[15]

In addition to formally named taxa, indeterminate anuran remains have been recovered from Morrison strata in Colorado, Wyoming, and Utah, with the best specimens found in Dinosaur National Monument and Quarry 9.[13] Stratigraphically speaking, indeterminate anurans have been found in stratigraphic zones 2 and 4.[7] Indeterminate anurans with remains diagnostic down to the family level have also been reported from the Morrison, with pelobatids being represented by the ilium of an unnamed and indeterminate species, which was recovered from Quarry 9.[16] Pelobatids are present in stratigraphic zones 5 and 6.[7]

Indeterminate salamander remains are present in stratigraphic zones 2, 4, and 5.[7] A distinctive type of salamander known only as Caudata B is present in stratigraphic zone 6.[7]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Name Species Locality Material Notes

Comobatrachus[13]

C. aenigmaticus

Wyoming, Brushy Basin member[13]

 A partial right humerus.[17]

A dubious genus of prehistoric frog erected by O. C. Marsh to house fragmentary remains recovered from Reed's Quarry 9 near Como Bluff Wyoming.[13] Along with Eobatrachus it was among the earliest frog remains from the formation, although the two dubious genera were erected decades apart.[13]

Comonecturoides[18]

C. marshi[18]

Wyoming, Brushy Basin member[18]

Represented by a single femur.[18]

Considered a nomen dubium because the name is based on non-distinctive remains which cannot be classified in detail.[18]

Enneabatrachus[9]

E. hechti[14]

Utah and Wyoming[19][14]

A small discoglossid frog whose live weight would have only been a few grams.[14]

Eobatrachus[13]

E. agilis

Wyoming, Brushy Basin member[13]

 A partial right humerus.[17]

A dubious genus of prehistoric frog erected by O. C. Marsh to house fragmentary remains recovered from Reed's Quarry 9 near Como Bluff Wyoming.[13] Along with Comobatrachus it was among the earliest frog remains from the formation, although the two dubious genera were erected decades apart.[13]

Iridotriton[9]

I. hechti

Utah, Brushy Basin[20]

 A partial skull and incomplete postcranial skeleton.[20]

A basal salamandroid closely related to today's advanced salamanders.

Rhadinosteus[9]

R. parvus[15]

Utah

Known from several slabs of rock which contain multiple partial specimens in association.[15]

A pipoid and possible rhinophrynid, Rhadinosteus parvus was only about 42 mm (1.6 inches) long in life.[15]

Sphenodonts
Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Name Species Locality Material Notes Images

Eilenodon[9]

E. robustus

Colorado

Several fragmentary skull, mandible, and tooth elements.

A herbivorous eilenodontine of relatively large size.

Opisthias[9]

O. rarus

Colorado, Utah and Wyoming, Brushy Basin member

Several skulls and partial skeletons.

A sphenodontian similar in appearance to the modern Tuatara

Opisthiamimus[21]

O. gregori

Northern Wyoming, possibly west-central Colorado. Brushy Basin Member

Most of the skull and postcranium

A small-bodied eusphenodontian, and one of the most complete rhynchocephalian taxa yet known from North America.

Theretairus[9]

T. antiquus

Wyoming, Brushy Basin member

A mandible.

A small sphenodontian.
Sphenodontia[21] Indeterminate Dinosaur National Monument A crushed partial skull (DINO 16454) The specimen is undescribed. Although previously considered to have belonged to Opisthias or Theretairus, recent studies have doubted this referral, thus placing it as an indeterminate sphenodont.[21]

Squamates

Numerous squamate remains have been found in the sediments of the Morrison Formation, most commonly at sites in Utah, Colorado and Wyoming. A number of taxa have been described, coming from three different groups: anguimorph and scincomorph lizards and early snakes.[22][23][24] The first squamates to be reported from the Morrison Formation were Paramacellodus and Dorsetisaurus, which were described from Wyoming's Quarry 9 by Don Prothero and Richard Estes.[22] Later remains would include Diablophis, originally described as a species of Parviraptor by Susan Evans in 1996[25] but subsequently moved to the new genus Diablophis by Michael Caldwell et al. in 2015, with extra material also being reported from Utah's Cisco Mammal Quarry, and Schillerosaurus, originally described as "Schilleria" and reported from Dinosaur National Monument by Evans and Dan Chure in 1999.[26] Two later additions to the Morrison's squamate assemblages are Eoscincus and Microteras, two scincomorph lizards found at Dinosaur National Monument and Como Bluff's Quarry 9, respectively. They were described by Chase Brownstein et al. in 2022.[23] Indeterminate squamate remains have currently been described from Dinosaur National Monument.[26]

The majority of modern-day scincomorph lizards are small insectivores that feed on a range of invertebrates.[27] It is thought that their counterparts from the Morrison Formation would have occupied a similar niche due to their morphological similarities. Anguimorph lizards most likely hunted small vertebrates, and Diablophis is thought to have done so too. Prey items would have included the other squamates from the formation as well as its large diversity of small mammals. All squamates might have been prey for the larger predators of the Morrison Formation, including the abundant theropod dinosaurs and crocodilians.

Name Species Locality Material Notes

Diablophis[24]

D. gilmorei

Fruita Palaeontological Area, Colorado and Cisco Mammal Quarry, Utah (Brushy Basin Member)

A broken right maxilla, broken right mandible and broken right dentary. Broken axis vertebrae, precloacal vertebrae, one caudal vertebra and a possible sacral vertebra have also been found. [24]

A basal snake.[24] Originally described as a species of Parviraptor,[9] subsequently moved to its own genus.[24]

Dorsetisaurus[9]

D. sp.

Quarry 9 at Como Bluff, Wyoming, Utah and Colorado (Brushy Basin Member)

Multiple dentaries. [22] [26]

An anguimorph lizard.

Eoscincus [23]

E. ornatus

Site 412 at Dinosaur National Monument, Utah (Brushy Basin Member)

The holotype specimen, DINO 14864, includes a complete rostrum and palate, a partial skull roof, and both mandibles.

A scincomorph lizard.

Microteras[23]

M. borealis

Quarry 9 at Como Bluff, Wyoming (Brushy Basin Member)

The holotype specimen, YPM VP 4718, consists of an associated maxilla and braincase.

A scincomorph lizard.

Paramacellodus[9]

P. sp.

Fruita Palaeontological Area & Rainbow Park, Colorado and Quarry 9 at Como Bluff, Wyoming (Brushy Basin Member)

Several jaws, two skulls, isolated jaw elements, osteoscutes and a small block bearing the posterior trunk vertebrae and hind limbs with a few ventral osteoscutes. Possibly a left prefrontal and postcranial material consisting of a scapulocoracoid, a trunk vertebra and multiple articulated bones consisting of a partial pelvis, seven caudal vertebrae and a nearly complete left hind limb.[22] [26]

A small scincomorph lizard with blunt teeth.

Saurillodon[9]

S. sp

Fruita Palaeontological Area, Colorado (Brushy Basin Member)

A scincomorph lizard whose remains have been found in Middle Jurassic strata in England and Scotland as well as Late Jurassic strata in Portugal in addition to the Morrison formation remains.[28]

Schillerosaurus[9] [29]

S. utahensis [30] [26]

Dinosaur National Monument, Utah (Brushy Basin Member)

Part and counterpart of a partial dissociated skeleton and a few limb bone fragments.[26]

A small scincomorph lizard of otherwise uncertain evolutionary affinities.[30] It is the only lizard genus endemic to the Morrison Formation.[30]

Squamata[26]

Indeterminate

Dinosaur National Monument, Utah (Brushy Basin Member)

Specimen DNM 14720.

A squamate of uncertain affinities. Noted as distinct from Paramacellodus and Dorsetisaurus, of which remains have been found in the same quarry.[26]

Turtles

Turtles (Testudines) are very common fossils in the Morrison, due to their bony shells. The most common were Glyptops plicatus (very common) and Dinochelys whitei (also common, but not as common as Glyptops). Also present were Dorsetochelys buzzops and Uluops uluops.

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Name Species Locality Material Notes

Chelonipus

Colorado and Utah, Salt Wash member

Compsemys

C. plicatulus

Colorado

Dinochelys[9]

D. whitei[31]

Colorado, Utah and Wyoming, Brushy Basin member[31]

Several shells and some postcranial material.[31]

Dorsetochelys[9]

D. buzzops

Glyptops[9]

G. plicatulus[31]

Colorado and Wyoming, Brushy Basin member[31]

Several shells, skulls, and partial skeletons.[31]

G. ornatus[32]

Wyoming, Brushy Basin member[32][31]

A skull.[31][32]

Synonym of Glyptops plicatulus.[31]

G. utahensis[33]

Utah, Brushy Basin member[33][31]

A complete shell.[33]

Synonym of Glyptops plicatulus.[31]

Uluops[9]

U. uluops

Wyoming, Brushy Basin member[34]

A cranium.[34]

Most basal Pleurosternid from the Morrison Formation.[34]

Choristoderes
Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Name Species Locality Material Notes

Cteniogenys[9]

C. antiquus

Colorado, Oklahoma, South Dakota, Utah and Wyoming

A champsosaur about 25 to 50 cm in length.

Crurotarsans

Crocodiles of a variety of sizes and habitats were common Morrison animals. Cursorial mesosuchians, or small terrestrial running crocs, included Hallopus victor and Fruitachampsa callisoni. More derived crocodilians included Diplosaurus ferox, Amphicotylus, Hoplosuchus kayi, and Macelognathus vagans.

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Name Species Locality Material Notes Images

Amphicotylus[35]

A. gilmorei

Wyoming
Hallopus
Hoplosuchus

A. lucasii

Colorado

A. milesi

Wyoming, Brushy Basin member[36]

A nearly complete skeleton.[36]

A. stovalli

Oklahoma

Diplosaurus[37]

D. felix

Colorado

Eutretauranosuchus[9]

E. delfsi

Colorado and Wyoming

Fruitachampsa[9]

F. callisoni

Colorado, Brushy Basin and Saltwash members

Hallopus[9]

H. victor

Colorado, Brushy Basin member[38]

A partial skeleton including a fragmentary skull roof.[38]

Hatcherichnus

H. sanjuanensis

Colorado and Utah

H. sp.

Utah and Wyoming, Salt Wash member

Hoplosuchus[9]

H. kayi

Arizona and Utah

Macelognathus[9]

M. vagans

Colorado and Wyoming, Brushy Basin member[39]

A partial left mandible (type) and several fragmentary referred fossils.[39]

Theriosuchus[40]

T. morrisonensis

Wyoming

A nearly complete left mandible missing teeth.

Pterosaurs

Pterosaurs are very uncommon fossils in the Morrison, because the fragility of their thin walled bones often prevented their remains from being preserved.[41] Despite being uncommon they are geographically widespread;[42] indeterminate pterosaur remains have been found in stratigraphic zones 2 and 4-6.[7] In addition to indeterminate remains, several species have been identified from both the rhamphorhynchoids (long-tailed pterosaurs) and pterodactyloids (short-tailed pterosaurs).[41] Since the 1970s and 80s, pterosaur finds have become more common, but are still rare.[41] Most Morrison pterosaurs have been found in marine and shoreline deposits.[41] Pterosaur tracks have been found in both the Tidwell and Saltwash members.[41] Morrison pterosaurs probably lived on fish, insects and scavenged dinosaur carcasses, or even foraged for prey, and actively hunted;[41] they are fairly ecologically diverse, ranging from small hawking insectivore Mesadactylus to the raptorial Harpactognathus. While relatively few pterosaur genera are named from the Morrison Formation, fragmentary material that is not referrable to the genus level suggests the presence of dsungaripteroids, ctenochasmatids, dimorphodontids, and more tentatively wukongopterids and pteranodontians.[43][44][45][46]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Name Species Locality Material Notes Images

Comodactylus[9]

C. ostromi

Wyoming, Brushy Basin member

A metacarpal.

Nomen dubium

Dermodactylus[9]

D. montanus

Wyoming, Brushy Basin member

A wing phalanx.

Nomen dubium

Harpactognathus[9]

H. gentryii

Wyoming, Brushy Basin member

A partial snout.

A large rhamphorhynchid with a wingspan of about 2.5 m and live mass of about 1.5 kg (3.3 lbs).[47] Harpactognathus was related to the Solnhofen genus Scaphognathus.[47]

Kepodactylus[9]

K. insperatus

Colorado, Brushy Basin member

A partial postcranial skeleton.

A large pterodactyloid with a 2.5 m (8 foot) wingspan and a live weight of about 1.5 kg (3 lbs).[48] Kepodactylus may be related to the Asian dsungaripteroid pterosaurs.[48]

Laopteryx[42]

L. priscus

Wyoming, Brushy Basin member

A braincase.

Nomen dubium initially misidentified as a bird.

Mesadactylus[9]

M. ornithosphyos

Colorado, Brushy Basin member

 A synsacrum. Several specimens have been incorrectly referred to Mesadactylus.[44][45]

Pteraichnus[49]

P. saltwashensis'*

Arizona and Oklahoma, Saltwash member

Utahdactylus[9]

U. kateae

Utah, Tidwell member

A fragmentary skeleton.

Previously thought to be an indeterminite diapsid, newer material suggests an affinity with ctenochasmatids.[46]

Dinosaurs
Main article: Dinosaurs of the Morrison Formation

Mammaliaforms

Many types of mammaliaform cynodonts, mostly early mammals, are known from the Morrison; almost all of them were small sized animals, though occupying a very large variety of ecological niches, from the more rodent-like multituberculates to the carnivorous eutriconodonts (including the possibly volant Triconolestes) to the anteater-like Fruitafossor. Unclassified types include the digger Fruitafossor windscheffelia. Docodonts included the common genus Docodon, represented by D. victor, D. striatus, and D. superbus, and Peraiocynodon sp. Multituberculates, a common type of early mammal, were represented by Ctenacodon serratus, C. laticeps, C. scindens, Glirodon grandis, Morrisonodon brentbaatar, Psalodon fortis, ?P. marshi, P. potens, and Zofiabaatar pulcher. Triconodonts present included Amphidon superstes, Aploconodon comoensis, Conodon gidleyi, Priacodon ferox, P. fruitaensis, P. gradaevus, P. lulli, P. robustus, Triconolestes curvicuspis, and Trioracodon bisulcus.

Tinodontids were represented by Eurylambia aequicrurius (probably Tinodon), and Tinodon bellus (including T. lepidus). Finally, two families of Dryolestoidea were present: Paurodontidae, including Comotherium richi, Euthlastus cordiformis, Paurodon valens, and Tathiodon agilis; and Dryolestidae, including Amblotherium gracilis, Dryolestes obtusus (common genus), D. priscus, D. vorax, Laolestes eminens, L. grandis, and Miccylotyrans minimus.

In 2009, a study by J. R. Foster was published which estimated the body masses of mammals from the Morrison Formation by using the ratio of dentary length to body mass of modern marsupials as a reference. Foster concludes that Docodon was the most massive mammaliaform genus of the formation at 141g and Fruitafossor was the least massive at 6g. The average Morrison mammal had a mass of 48.5g. A graph of the body mass distribution of Morrison mammal genera produced a right-skewed curve, meaning that there were more low-mass genera.[50]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Tinodontids
Name Species Locality Material Notes

Eurylambia

E. aequicrurius

Wyoming

A tinodontid similar in appearance to Tinodon.

Tinodon[9]

T. bellus

Wyoming

Tinodontids.

T. lepidus

Wyoming

Eutriconodonts
Name Species Locality Material Notes

Amphidon[9]

A. superstes

Wyoming

A small amphidontid.

Aploconodon[9]

A. comoensis

Wyoming

An amphilestid eutriconodont.

Comodon[9]

C. gidleyi

Wyoming, Brushy Basin member

 A mandible.

An amphilestid eutriconodont slightly larger in size than Aploconodon.

Phascalodon

P. gidleyi

Wyoming

Triconolestes[9]

T. curvicuspis

Utah

A volaticotherian eutriconodont.

Trioracodon[9]

T. bisulcus

Wyoming

A triconodontid eutriconodont similar to Priacodon.

Multituberculates
Name Species Locality Material Notes

Ctenacodon[9]

C. laticeps

Wyoming

C. scindens

C. serratus

Wyoming

Glirodon[9]

G. grandis

Colorado and Utah

Morrisonodon

M. brentbaatar

Wyoming

Priacodon[9]

P. ferox

Wyoming

P. fruitaensis

Colorado

P. grandaevus

Wyoming

P. lulli

Wyoming

P. robustus

Wyoming

Psalodon[9]

P. fortis

P. marshi

P. potens

Zofiabaatar[9]

Z. pulcher

Wyoming

Others
Name Species Locality Material Notes Images

Cifellilestes[51]

C. ciscoensis[51]

Utah, Brushy Basin Member
Fruitafossor

Docodon[9]

D. victor[52]

Fruitafossor[9]

F. windscheffeli

 Colorado

Dryolestoids
Name Species Locality Material Notes

Amblotherium[9]

A. gracilis

Colorado

A small Dryolestid dryolestoid.

A. megistodon[53]

Wyoming

Araeodon[9]

A. intermissus

Utah and Wyoming

A paurodontid dryolestoid, somewhat smaller than Archaeotrigon and Paurodon. Considered to be a junior synonym of Paurodon valens by Averianov and Martin (2015).[54]

Archaeotrigon[9]

A. brevimaxillus

Wyoming

Paurodontid dryolestoids similar in appearance to Paurodon. Both species were considered to be junior synonyms of Paurodon valens by Averianov and Martin (2015).[54]

A. distagmus

Comotherium[9]

C. richi

Wyoming

A paurodontid dryolestoid.

Dryolestes[9]

D. obtusus

Dryolestid dryolestoids.

D. priscus

Wyoming

D. tenax

Euthlastus[9]

E. cordiformis

Wyoming

A paurodontid dryolestoid.

Foxraptor[9]

F. atrox

Wyoming

A paurodontid dryolestoid similar in size to Paurodon. Considered to be a junior synonym of Paurodon valens by Averianov and Martin (2015).[54]

Herpetairus

H. sp.

Kepolestes

K. coloradensis

Colorado

Laolestes[9]

L. eminens

Common Dryolestid dryolestoids.

L. grandis

Malthacolestes

M. sp.

Melanodon

M. goodrichi

M. hodsoni

M. oweni

Miccylotyrans

M. minimus

A Dryolestid dryolestoid.

Paurodon[9]

P. valens

Wyoming

A paurodontid dryolestoid.

Pelicopsis

P. dubius

Wyoming

A paurodontid dryolestoid. Considered to be a junior synonym of Paurodon valens by Averianov and Martin (2015).[54]

Tathiodon[9]

T. agilis

Wyoming

A paurodontid dryolestoid.

See also

Footnotes
  1. Steven R. Manchester; Xiaoqing Zhang; Carol L. Hotton; Scott Wing; Peter R. Crane (2022). "Two-seeded cones of probable gnetalean affinity from the Morrison Formation (Late Jurassic) of Utah and Colorado, USA". Acta Palaeobotanica. 62 (2): 77–92. doi:10.35535/acpa-2022-0006.
  2. Steven R. Manchester; Xiaoqing Zhang; Carol L. Hotton; Scott Wing; Peter R. Crane (2021). "Distinctive quadrangular seed-bearing structures of gnetalean affinity from the Late Jurassic Morrison Formation of Utah, USA". Journal of Systematic Palaeontology. 19 (4): 1–18. doi:10.1080/14772019.2021.1968522. S2CID 239021014.
  3. Elliott Armour Smith; Mark A. Loewen; James I. Kirkland (2020). "New social insect nests from the Upper Jurassic Morrison Formation of Utah". Geology of the Intermountain West. 7: 281–299. doi:10.31711/giw.v7.pp281-299.
  4. María B. Lara; John R. Foster; James I. Kirkland; Thomas F. Howells (2020). "First fossil true water bugs (Heteroptera, Nepomorpha) from Upper Jurassic strata of North America (Morrison Formation, southeastern Utah)". Historical Biology: An International Journal of Paleobiology. 33 (10): 1996–2004. doi:10.1080/08912963.2020.1755283. S2CID 219470267.
  5. D. M. Smith, M. A. Gorman, J. D. Pardo and B. J. Small. 2011. First fossil Orthoptera from the Jurassic of North America. Journal of Paleontology 85(1):102-105
  6. Foster, J. (2007). "The Forgotten Aquatic Denizens: The Fish." pp. 129-131.
  7. Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329.
  8. Foster, J. (2007). "Pycnodontoidea." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. p. 135.
  9. Foster, J. (2007). "Table 2.1: Fossil Vertebrates of the Morrison Formation." pp. 58-59.
  10. Foster, J. (2007). "Hulettia hawesi." p. 132-134.
  11. Foster, J. (2007). "cf. Leptolepis." p. 135.
  12. Foster, J. (2007). "Morrolepis schaefferi." pp. 131-132.
  13. Foster, J. (2007). "Anura (Frogs)." pp. 135-136.
  14. Foster, J. (2007). "Enneabatrachus hechti" p. 137.
  15. Foster, J. (2007). "Rhadinosteus parvus." p. 137.
  16. Foster, J. (2007). "Pelobatidae indet." p. 137.
  17. Evans, S. E. and Milner, A. R. (1993). Frogs and salamanders from the Upper Jurassic Morrison Formation (Quarry Nine, Como Bluff) of North America. Journal of Vertebrate Paleontology 13(1):24-30
  18. Foster, J. (2007). "Caudata (Salamanders)" p. 138.
  19. Foster, J. (2007). "Enneabatrachus hechti" p. 137. Note that Dinosaur National Monument is in Utah, see ibid. pg. 6.
  20. Evans, S. E., Lally, C., Chure, D. C., Elder, A., & Maisano, J. A. (2005). A late Jurassic salamander (Amphibia: Caudata) from the Morrison formation of north America. Zoological Journal of the Linnean Society, 143(4), 599-616.
  21. DeMar Jr, D. G.; Jones, M. E. H.; Carrano, M. T. (2022). "A nearly complete skeleton of a new eusphenodontian from the Upper Jurassic Morrison Formation, Wyoming, USA, provides insight into the evolution and diversity of Rhynchocephalia (Reptilia: Lepidosauria)". Journal of Systematic Palaeontology. 20 (1): 779–786. doi:10.1080/14772019.2022.2093139. PMID 2093139.
  22. Prothero, D. R.; Estes, R. (1980). "Late Jurassic lizards from Como Bluff, Wyoming and their palaeobiogeographic significance". Nature. 286 (5772): 484–486. doi:10.1038/286484a0. S2CID 4333094.
  23. Brownstein, C. D.; Meyer, D. L.; Fabbri, M.; Bhullar, B. S.; Gauthier, J. A. (2022). "Evolutionary origins of the prolonged extant squamate radiation". Nature Communications. 13 (7087): 7087. doi:10.1038/s41467-022-34217-5. PMC 9708687. PMID 36446761.
  24. Caldwell, M. W.; Nydam, R. L.; Palci, A.; Apesteguía, S. N. (2015). "The oldest known snakes from the Middle Jurassic-Lower Cretaceous provide insights on snake evolution". Nature Communications. 6: 1–11. Bibcode:2015NatCo...6.5996C. doi:10.1038/ncomms6996. PMID 25625704.
  25. Evans, S.E. (1996). "Parviraptor (Squamata: Anguimorpha) and Other Lizards from the Morrison Formation at Fruita, Colorado". The Continental Jurassic. 60: 243–248.
  26. Evans, S. E.; Chure, D. J. (1999). "Upper Jurassic lizards from the Morrison Formation of Dinosaur National Monument, Utah". Vertebrate Paleontology in Utah. Miscellaneous Publications of the Utah Geological Survey. 99 (1): 151–159.
  27. Benton, M. J. (2015). Vertebrate palaeontology (4th ed.). Chichester, West Sussex. ISBN 978-1-118-40764-6. OCLC 867852756.{{cite book}}: CS1 maint: location missing publisher (link)
  28. Foster, J. (2007). "Saurillodon sp." p. 145.
  29. Randall L. Lydam, Daniel J. Chure and Susan E. Evans (2013). "Schillerosaurus gen. nov., a replacement name for the lizard genus Schilleria Evans and Chure, 1999 a junior homonym of Schilleria Dahl, 1907" (PDF). Zootaxa. 3734 (1): 99–100. doi:10.11646/zootaxa.3736.1.6. PMID 25112616.
  30. Foster, J. (2007). "Schilleria utahensis" p. 145.
  31. Gaffney, E. S. (1979). The Jurassic turtles of North America. Bulletin of the AMNH; v. 162, article 3.
  32. Marsh, Othniel Charles (1890-08-01). "Notice of some extinct Testudinata". American Journal of Science. s3-40 (236): 177–179. Bibcode:1890AmJS...40..177M. doi:10.2475/ajs.s3-40.236.177. ISSN 0002-9599. S2CID 130897765.
  33. Gilmore, C. (1912). Description of a new species of tortoise from the Jurassic of Utah. Annals of the Carnegie Museum 10:7–12.
  34. Rollot, Yann; Evers, Serjoscha W.; Joyce, Walter G. (2021-10-06). "A redescription of the Late Jurassic (Tithonian) turtle Uluops uluops and a new phylogenetic hypothesis of Paracryptodira". Swiss Journal of Palaeontology. 140 (1): 23. doi:10.1186/s13358-021-00234-y. ISSN 1664-2384. PMC 8550081. PMID 34721284.
  35. Pritchard, A. C.; Turner, A. H.; Allen, E. R.; Norell, M. A. (2013). "Osteology of a North American Goniopholidid (Eutretauranosuchus delfsi) and Palate Evolution in Neosuchia". American Museum Novitates 3783 (3783): 1. doi:10.1206/3783.2. edit
  36. Yoshida, Junki; Hori, Atsushi; Kobayashi, Yoshitsugu; Ryan, Michael J.; Takakuwa, Yuji; Hasegawa, Yoshikazu (2021). "A new goniopholidid from the Upper Jurassic Morrison Formation, USA: novel insight into aquatic adaptation toward modern crocodylians". Royal Society Open Science. 8 (12): 210320. Bibcode:2021RSOS....810320Y. doi:10.1098/rsos.210320. PMC 8652276. PMID 34909210.
  37. Allen, Eric Randall (Summer 2012). "Analysis of North American goniopholidid crocodyliforms in a phylogenetic context" (pdf). doi:10.17077/etd.317zy27t. {{cite journal}}: Cite journal requires |journal= (help)
  38. A. D. Walker. A Revision of the Jurassic Reptile Hallopus victor (Marsh), with Remarks on the Classification of Crocodiles. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences Vol. 257, No. 816 (Feb. 26, 1970), pp. 323-372
  39. Göhlich, U., L.M. Chiappe, J.M. Clark, and H.-D. Sues (2005) The systematic position of the Late Jurassic alleged dinosaur Macelognathus (Crocodylomorpha: Sphenosuchia). Canadian Journal of Earth Sciences 42: 307–321.
  40. Foster, J. (2018). "A new atoposaurid crocodylomorph from the Morrison Formation (Upper Jurassic) of Wyoming, USA". Geology of the Intermountain West. 5: 287–295. doi:10.31711/giw.v5i0.32. ISSN 2380-7601.
  41. Foster, J. (2007). "Soaring Overhead: The Pterosaurs." pp. 157-158.
  42. Foster, J. (2007). "Laopteryx priscus." p. 160.
  43. Jensen, J. A., and Padian, K. (1989) Small pterosaurs and dinosaurs from the Uncompahgre fauna (Brushy Basin Member, Morrison Formation: ?Tithonian), late Jurassic, western Colorado. Journal of Paleontology 63:363–374.
  44. McLain, M. A., & Bakker, R. T. (2018). Pterosaur material from the uppermost Jurassic of the uppermost Morrison Formation, Breakfast Bench Facies, Como Bluff, Wyoming, including a pterosaur with pneumatized femora. Geological Society, London, Special Publications, 455(1), 105-124.
  45. Sprague, M. & McLain, M. A. (2018). Resolving the Mesadactylus Complex of Dry Mesa Quarry, Morrison Formation, Colorado. Journal of Vertebrate Paleontology, Program and Abstracts, 2018, p. 220.
  46. Stephen Czerkas; Tracy Ford (2018). "Pterosaur or diapsid? The search for the true Utahdactylus". Flugsaurier 2018: The 6th International Symposium on Pterosaurs. Los Angeles, USA. Abstracts: 35–36.
  47. Foster, J. (2007). "Harpactognathus gentryii." p. 160.
  48. Foster, J. (2007). "Kepodactylus insperatus." p. 160.
  49. Lockley et al. (2008).
  50. Foster, J.R. 2009. Preliminary body mass estimates for mammalian genera of the Morrison Formation (Upper Jurassic, North America). PaleoBios 28(3):114-122.
  51. Brian M. Davis; Kai R.K. Jäger; Guillermo W. Rougier; Kelli Trujillo; Kevin Chamberlain (2022). "A morganucodontan mammaliaform from the Upper Jurassic Morrison Formation, Utah, USA". Acta Palaeontologica Polonica. doi:10.4202/app.00955.2021.
  52. Julia A. Schultz; Bhart-Anjan S. Bhullar; Zhe-Xi Luo (2018). "Re-examination of the Jurassic mammaliaform Docodon victor by computed tomography and occlusal functional analysis". Journal of Mammalian Evolution. in press. doi:10.1007/s10914-017-9418-5.
  53. John R. Foster; Darrin C. Pagnac; ReBecca K. Hunt-Foster (2020). "An unusually diverse northern biota from the Morrison Formation (Upper Jurassic), Black Hills, Wyoming". Geology of the Intermountain West. 7: 29–67. doi:10.31711/giw.v7.pp29-67.
  54. A.O. Averianov and T. Martin (2015). "Ontogeny and taxonomy of Paurodon valens (Mammalia, Cladotheria) from the Upper Jurassic Morrison Formation of USA" (PDF). Proceedings of the Zoological Institute of the Russian Academy of Sciences. 319 (3): 326–340.

Bibliography
Wikimedia Commons has media related to Paleobiota of the Morrison Formation.
  • Foster, J. (2007). Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. 389pp. ISBN 978-0-253-34870-8
  • Lockley, M.; Harris, J.D.; and Mitchell, L. 2008. "A global overview of pterosaur ichnology: tracksite distribution in space and time." Zitteliana. B28. p. 187-198. ISSN 1612-4138
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