Paleobiota of the Morrison Formation#Mammaliaforms
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File:Green River UT 2005-10-14 2104.jpg and the source of fossils like those found at the Dinosaur Quarry.]]
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.
Plants
The Morrison Formation is devoid of flowering plants; during the Jurassic, the Earth was dominated by ferns, seed ferns, and a wealth of gymnosperms—such as cycads, ginkgos, and conifers. Vegetation varied from river-lining forests of conifers, tree ferns, and ferns (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum.{{cite book |last=Carpenter |first=Kenneth |author-link=Kenneth Carpenter |year=2006 |chapter=Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus |editor=Foster, John R. |editor2=Lucas, Spencer G. |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |series=New Mexico Museum of Natural History and Science Bulletin, 36 |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque, New Mexico |pages=131–138 }}{{cite journal |last1=Peterson |first1=Fred |title=SUMMARY LIST OF LATE JURASSIC PLANTS, WESTERN INTERIOR U.S. & SW CANADA}}
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=Conifers=
| class="wikitable" align="center" width="100%" |
| Genus
! Species ! Locality ! Material ! Notes |
|---|
| style="background:#D1FFCF;" |Mesembrioxylon{{Citation needed|date=February 2025}}
|style="background:#D1FFCF;" | M. carterii |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |
| style="background:#D1FFCF;" |Protocupressinoxylon{{Citation needed|date=February 2025}}
|style="background:#D1FFCF;" | P. medlynii |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |
| style="background:#D1FFCF;" |Brachyphyllum{{Citation needed|date=February 2025}}
|style="background:#D1FFCF;" |B. rechtenii B. sp |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |
| style="background:#D1FFCF;" |Sequoia{{Citation needed|date=February 2025}}
|style="background:#D1FFCF;" |S.sp |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |
| style="background:#D1FFCF;" |cf. Araucaria{{cite journal |last1=Bader |first1=K |title=The local flora and fauna of a site in the upper Morrison Formation (Upper Jurassic) of northeastern Wyoming. |journal=Journal of Vertebrate Paleontology |date=2003 |volume=23 |issue=3 suppl}}
|style="background:#D1FFCF;" |A. sp |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |
= Ginkgos =
| class="wikitable" align="center" width="100%" |
| Genus
! Species ! Locality ! Material ! Notes |
|---|
| style="background:#D1FFCF;" |Ginkgo{{Citation needed|date=February 2025}}
|style="background:#D1FFCF;" | G. sp |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |
= Cycadophyta and relatives =
| class="wikitable" align="center" width="100%" |
| Genus
! Species ! Locality ! Material ! Notes |
|---|
| style="background:#D1FFCF;" |Nilssonia{{Citation needed|date=February 2025}}
|style="background:#D1FFCF;" | N. compta |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |
| style="background:#D1FFCF;" |Zamites{{Citation needed|date=February 2025}}
|style="background:#D1FFCF;" | Z. arcticus |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |
| style="background:#D1FFCF;" |Cycadolepis{{Citation needed|date=February 2025}}
|style="background:#D1FFCF;" | C. sp |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |style="background:#D1FFCF;" | |
=Gnetales=
Invertebrates
= Arthropods =
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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. Although abundant, fish remains are constrained to only certain locations within the formation. Microvertebrate sites in Wyoming are dominated by fish remains. Indeterminate ray-finned fish remains have been recovered from Ninemile Hill and a microvertebrate site in the Black Hills. Found in stratigraphic zones 2, 4, and 5. Morrison actinopterygians generally have no close modern relatives. The Wyoming microvertebrate remains are extracted from the sediment by screenwashing. Paleoniscoid remains are geographically present in the western part of Colorado, where remains have been recovered from "a level above the Mygatt-Moore Quarry." Largely complete remains of small individuals have been consistently recovered for over 15 years. Single tooth fossil of pycnodont fish is represented from Dinosaur National Monument in Utah,Foster, J. (2007). "Pycnodontoidea." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. p. 135. found in stratigraphic zone 4. Dipnoan remains found at a fossil site not far from Cañon City, Colorado. Remains usually in a state of rather complete preservation. Halecostome remains are geographically present in the western part of Colorado, where remains have been recovered from "a level above the Mygatt-Moore Quarry." Largely complete remains of small individuals have been consistently recovered for over 15 years. Amiid remains found in stratigraphic zones 2, 3, and 4.Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329. Found at a fossil site not far from Cañon City, Colorado. Remains usually in a state of rather complete preservation.
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| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes ! Images |
|---|
| rowspan=5 |
| C. fossanovumFoster, J. (2007). "The Forgotten Aquatic Denizens: The Fish." pp. 129-131. | | | rowspan=4 | 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. These species are believed to have had similar diets to extant lungfish like the physically similar modern genus Neoceratodus. | rowspan=10 | |
| C. ?frazieri
| | |
| style="background:#fbdddb;" |
|style="background:#fbdddb;" | |style="background:#fbdddb;" | |
| C. robustus
| | |
| Indeterminate.
| Brushy Basin and Saltwash members | | Represented by tooth plates. |
| Hulettia
| H. hawesiFoster, J. (2007). "Hulettia hawesi." p. 132-134. | 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
| N/A | | Known only from a single nearly complete skeleton found at Rabbit Valley.Foster, J. (2007). "cf. Leptolepis." p. 135. Found in stratigraphic zone 5. | A 13 cm (5 inch) fish that was deeper bodied than its co-occurring contemporaries Morrolepis and Hulettia. The Morrison cf. Leptolepis probably had a live mass of about 37g. It is the only teleost fish known from the formation and was morphologically more highly derived than other Morrison fish. It is believed to have fed on contemporary fish and small invertebrates. |
| Morrolepis
| M. schaefferiFoster, J. (2007). "Morrolepis schaefferi." pp. 131-132. | 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. Adult specimens would reach about 20 cm in length and 113 g (4 oz) in mass. |
| Potamoceratodus
| P. guentheri | Colorado | | Once thought to be a species of Ceratodus. |
| A hybodont?
| Indeterminate | Utah | | |
= Amphibians =
File:Rhinophrynus dorsalis.jpg
Frogs are known from several sites in the Morrison Formation, but are not particularly well represented.Foster, J. (2007). "Anura (Frogs)." pp. 135-136. 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 and Rhadinosteus parvus.
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. Stratigraphically speaking, indeterminate anurans have been found in stratigraphic zones 2 and 4. 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.Foster, J. (2007). "Pelobatidae indet." p. 137. Pelobatids are present in stratigraphic zones 5 and 6.
Indeterminate salamander remains are present in stratigraphic zones 2, 4, and 5. A distinctive type of salamander known only as Caudata B is present in stratigraphic zone 6.
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| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! width="20%"| Material ! width="40%"| Notes |
|---|
| style="background:#E6E6E6;"|
|style="background:#E6E6E6;"| C. aenigmaticus |style="background:#E6E6E6;"| |style="background:#E6E6E6;"| A partial right humerus.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 |style="background:#E6E6E6;"| 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. Along with Eobatrachus it was among the earliest frog remains from the formation, although the two dubious genera were erected decades apart. |
| style="background:#E6E6E6;"|
ComonecturoidesFoster, J. (2007). "Caudata (Salamanders)" p. 138. |style="background:#E6E6E6;"| |style="background:#E6E6E6;"| |style="background:#E6E6E6;"| Represented by a single femur. |style="background:#E6E6E6;"| Considered a nomen dubium because the name is based on non-distinctive remains which cannot be classified in detail. |
| EnneabatrachusFoster, J. (2007). "Table 2.1: Fossil Vertebrates of the Morrison Formation." pp. 58-59.
| E. hechtiFoster, J. (2007). "Enneabatrachus hechti" p. 137. | Utah and WyomingFoster, J. (2007). "Enneabatrachus hechti" p. 137. Note that Dinosaur National Monument is in Utah, see ibid. pg. 6. | | A small discoglossid frog whose live weight would have only been a few grams. |
| style="background:#E6E6E6;"|
|style="background:#E6E6E6;"| E. agilis |style="background:#E6E6E6;"| |style="background:#E6E6E6;"| A partial right humerus. |style="background:#E6E6E6;"| 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. Along with Comobatrachus it was among the earliest frog remains from the formation, although the two dubious genera were erected decades apart. |
| Iridotriton
| I. hechti | |A partial skull and incomplete postcranial skeleton. | A basal salamandroid closely related to today's advanced salamanders. |
| Rhadinosteus
| R. parvusFoster, J. (2007). "Rhadinosteus parvus." p. 137. | Utah | Known from several slabs of rock which contain multiple partial specimens in association. | A pipoid and possible rhinophrynid, Rhadinosteus parvus was only about 42 mm (1.6 inches) long in life. |
= Sphenodonts =
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| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes !Images |
|---|
| Eilenodon
| E. robustus | Colorado | Several fragmentary skull, mandible, and tooth elements. | A herbivorous eilenodontine of relatively large size. |
| Opisthias
| O. rarus | Colorado, Utah and Wyoming, Brushy Basin member | Several skulls and partial skeletons. | |
| Opisthiamimus{{Cite journal | doi = 10.1080/14772019.2022.2093139| title = 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 = Journal of Systematic Palaeontology| volume = 20| issue = 1| pages = 779–786| year = 2022| last1 = DeMar Jr | first1 = D. G. | last2 = Jones | first2 = M. E. H. | last3 = Carrano | first3 = M. T. | pmid=2093139| doi-access = free | hdl = 2440/136608| hdl-access = free}}
| 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
| T. antiquus | Wyoming, Brushy Basin member | A mandible. | A small sphenodontian. |
| Sphenodontia
|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. |
=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. 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. Later remains would include Diablophis, originally described as a species of Parviraptor by Susan Evans in 1996{{cite journal |author=Evans, S.E. |year=1996 |title=Parviraptor (Squamata: Anguimorpha) and Other Lizards from the Morrison Formation at Fruita, Colorado |journal=The Continental Jurassic |volume=60 |pages=243–248}} 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. 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. Indeterminate squamate remains have currently been described from Dinosaur National Monument.
The majority of modern-day scincomorph lizards are small insectivores that feed on a range of invertebrates.{{Cite book |last=Benton |first=M. J. |url=https://www.worldcat.org/oclc/867852756 |title=Vertebrate palaeontology |date=2015 |isbn=978-1-118-40764-6 |edition=4th |location=Chichester, West Sussex |oclc=867852756}} 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.
= 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.
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| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes |
|---|
| style="background:#FEF6E4;"|
|style="background:#FEF6E4;"| |style="background:#FEF6E4;"| Colorado and Utah, Salt Wash member |style="background:#FEF6E4;"| |style="background:#FEF6E4;"| |
| Compsemys
|style="background:#fbdddb;" | C. plicatulus |style="background:#fbdddb;" | Colorado |style="background:#fbdddb;" | |style="background:#fbdddb;" | |
| Dinochelys
| | Colorado, Utah and Wyoming, Brushy Basin member | Several shells and some postcranial material. | |
| Dorsetochelys
| D. buzzops | | | |
| rowspan="3" |
| | Colorado and Wyoming, Brushy Basin member | Several shells, skulls, and partial skeletons. | |
| style="background:#E6E6E6;" |
|style="background:#E6E6E6;" | |style="background:#E6E6E6;" | |style="background:#E6E6E6;" | |
| style="background:#E6E6E6;" |
|style="background:#E6E6E6;" | |style="background:#E6E6E6;" | |style="background:#E6E6E6;" | |
| Uluops
| U. uluops | Wyoming, Brushy Basin member{{Cite journal |last1=Rollot |first1=Yann |last2=Evers |first2=Serjoscha W. |last3=Joyce |first3=Walter G. |date=2021-10-06 |title=A redescription of the Late Jurassic (Tithonian) turtle Uluops uluops and a new phylogenetic hypothesis of Paracryptodira |journal=Swiss Journal of Palaeontology |language=en |volume=140 |issue=1 |pages=23 |doi=10.1186/s13358-021-00234-y |issn=1664-2384 |pmc=8550081 |pmid=34721284 |doi-access=free |bibcode=2021SwJP..140...23R }} | | |
= Choristoderes =
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| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes |
|---|
| Cteniogenys
| C. antiquus | Colorado, Oklahoma, South Dakota, Utah and Wyoming | | A choristoderan 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.
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= Pterosaurs =
Pterosaurs are very uncommon fossils in the Morrison, because the fragility of their thin walled bones often prevented their remains from being preserved.Foster, J. (2007). "Soaring Overhead: The Pterosaurs." pp. 157-158. Despite being uncommon they are geographically widespread;Foster, J. (2007). "Laopteryx priscus." p. 160. indeterminate pterosaur remains have been found in stratigraphic zones 2 and 4-6. In addition to indeterminate remains, several species have been identified from both the rhamphorhynchoids (long-tailed pterosaurs) and pterodactyloids (short-tailed pterosaurs). Since the 1970s and 80s, pterosaur finds have become more common, but are still rare. Most Morrison pterosaurs have been found in marine and shoreline deposits. Pterosaur tracks have been found in both the Tidwell and Saltwash members. Morrison pterosaurs probably lived on fish, insects and scavenged dinosaur carcasses, or even foraged for prey, and actively hunted; 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.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.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.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.
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| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes ! Images |
|---|
| style="background:#E6E6E6;"|
|style="background:#E6E6E6;"| C. ostromi |style="background:#E6E6E6;"| Wyoming, Brushy Basin member |style="background:#E6E6E6;"| A metacarpal. |style="background:#E6E6E6;"| | rowspan="8" | |
| style="background:#E6E6E6;"|
|style="background:#E6E6E6;"| D. montanus |style="background:#E6E6E6;"| Wyoming, Brushy Basin member |style="background:#E6E6E6;"| A metacarpal. |style="background:#E6E6E6;"| |
| Harpactognathus
| 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). Harpactognathus was related to the Solnhofen genus Scaphognathus.Foster, J. (2007). "Harpactognathus gentryii." p. 160. |
| Kepodactylus
| 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). Kepodactylus may be related to the Asian dsungaripteroid pterosaurs.Foster, J. (2007). "Kepodactylus insperatus." p. 160. |
| style="background:#E6E6E6;"|
|style="background:#E6E6E6;"| L. priscus |style="background:#E6E6E6;"| Wyoming, Brushy Basin member |style="background:#E6E6E6;"| A braincase. |style="background:#E6E6E6;"| Nomen dubium initially misidentified as a bird. |
| Mesadactylus
| M. ornithosphyos | Colorado, Brushy Basin member |A synsacrum. |Several specimens have been incorrectly referred to Mesadactylus.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. |
| style="background:#FEF6E4;"|
PteraichnusLockley et al. (2008). |style="background:#FEF6E4;"| P. saltwashensis* |style="background:#FEF6E4;"| Arizona and Oklahoma, Saltwash member |style="background:#FEF6E4;"| |style="background:#FEF6E4;"| |
| style="background:#E6E6E6;"|
|style="background:#E6E6E6;"| U. kateae |style="background:#E6E6E6;"| Utah, Tidwell member |style="background:#E6E6E6;"| A fragmentary skeleton. |style="background:#E6E6E6;"| Previously thought to be an indeterminite diapsid, newer material suggests an affinity with ctenochasmatids. |
= Dinosaurs =
{{Main|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, Comodon 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.Foster, J.R. 2009. Preliminary body mass estimates for mammalian genera of the Morrison Formation (Upper Jurassic, North America). PaleoBios 28(3):114-122.
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== Tinodontids ==
| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes |
|---|
| Eurylambia
| E. aequicrurius | Wyoming | | A tinodontid similar in appearance to Tinodon. |
| rowspan=2 |
| T. bellus | Wyoming | | rowspan=2 | |
| T. lepidus
| Wyoming | |
== Eutriconodonts ==
| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes |
|---|
| Amphidon
| A. superstes | Wyoming | | A small amphidontid. |
| Aploconodon
| A. comoensis | Wyoming | | |
| Comodon
| C. gidleyi | Wyoming, Brushy Basin member |A mandible. | An amphilestid eutriconodont slightly larger in size than Aploconodon. |
| style="background:#fbdddb;" |
|style="background:#fbdddb;" | P. gidleyi |style="background:#fbdddb;" | Wyoming |style="background:#fbdddb;" | |style="background:#fbdddb;" | |
| Triconolestes
| T. curvicuspis | Utah | | |
| Trioracodon
| T. bisulcus | Wyoming | | A triconodontid eutriconodont similar to Priacodon. |
== Multituberculates ==
| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes |
|---|
| rowspan=3 |
| C. laticeps | Wyoming | | |
| C. scindens
| | | |
| C. serratus
| Wyoming | | |
| Glirodon
| G. grandis | Colorado and Utah | | |
| Morrisonodon
| M. brentbaatar | Wyoming | | |
| rowspan=5 |
| P. ferox | Wyoming | | rowspan=5 | |
| P. fruitaensis
| Colorado | |
| P. grandaevus
| Wyoming | |
| P. lulli
| Wyoming | |
| P. robustus
| Wyoming | |
| rowspan=3 |
| P. fortis | | | rowspan=3 | |
| P. marshi
| | |
| P. potens
| | |
| Zofiabaatar
| Z. pulcher | Wyoming | | |
== Others ==
| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes ! Images |
|---|
| CifellilestesBrian 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.
| | Utah, Brushy Basin Member | | |rowspan="3"|File:Fruitafossor BW.jpg]] |
| Docodon
| | | | |
| Fruitafossor
| F. windscheffeli |Colorado | | |
== Dryolestoids ==
| class="wikitable" align="center" width="100%" |
| Name
! Species ! Locality ! Material ! Notes |
|---|
| rowspan="2" |
| A. gracilis | Colorado | | rowspan="2" | A small Dryolestid dryolestoid. |
| A. megistodon{{Cite journal|author1=John R. Foster |author2=Darrin C. Pagnac |author3=ReBecca K. Hunt-Foster |year=2020|title=An unusually diverse northern biota from the Morrison Formation (Upper Jurassic), Black Hills, Wyoming |journal=Geology of the Intermountain West |volume=7 |pages=29–67 |doi=10.31711/giw.v7.pp29-67 |doi-access=free }}
| Wyoming | |
| Araeodon
| 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). |
| rowspan="2" |
| A. brevimaxillus | Wyoming | | rowspan="2" | Paurodontid dryolestoids similar in appearance to Paurodon. Both species were considered to be junior synonyms of Paurodon valens by Averianov and Martin (2015).{{Cite journal|author=A.O. Averianov and T. Martin |year=2015 |title=Ontogeny and taxonomy of Paurodon valens (Mammalia, Cladotheria) from the Upper Jurassic Morrison Formation of USA |journal=Proceedings of the Zoological Institute of the Russian Academy of Sciences |volume=319 |issue=3 |pages=326–340 |url=http://www.zin.ru/journals/trudyzin/doc/vol_319_3/TZ_319_3_Averyanov.pdf }} |
| A. distagmus
| | |
| Comotherium
| C. richi | Wyoming | | |
| rowspan="3" |
| D. obtusus | | | rowspan="3" | |
| D. priscus
| Wyoming | |
| D. tenax
| | |
| Euthlastus
| E. cordiformis | Wyoming | | |
| Foxraptor
| 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). |
| style="background:#E6E6E6;" |
| style="background:#E6E6E6;" | H. sp. | style="background:#E6E6E6;" | | style="background:#E6E6E6;" | | style="background:#E6E6E6;" | |
| style="background:#E6E6E6;" |
| style="background:#E6E6E6;" | K. coloradensis | style="background:#E6E6E6;" | Colorado | style="background:#E6E6E6;" | | style="background:#E6E6E6;" | |
| rowspan="2" |
| L. eminens | | | rowspan="2" | Common Dryolestid dryolestoids. |
| L. grandis
| | |
| style="background:#E6E6E6;" |
| style="background:#E6E6E6;" | M. sp. | style="background:#E6E6E6;" | | style="background:#E6E6E6;" | | style="background:#E6E6E6;" | |
| style="background:#E6E6E6;" |
| style="background:#E6E6E6;" | M. goodrichi M. hodsoni M. oweni | style="background:#E6E6E6;" | | style="background:#E6E6E6;" | | style="background:#E6E6E6;" | |
| Miccylotyrans
| M. minimus | | | |
| Paurodon
| P. valens | Wyoming | | |
| Pelicopsis
| P. dubius | Wyoming | | A paurodontid dryolestoid. Considered to be a junior synonym of Paurodon valens by Averianov and Martin (2015). |
| Tathiodon
| T. agilis | Wyoming | | |
See also
{{Portal|Paleontology}}
- List of dinosaur-bearing rock formations
- [https://web.archive.org/web/20110716052504/http://rogov.zwz.ru/Joliaf/Yen%20Teng-chien,%20Reeside,%201946.pdf Molluscs]
- [https://web.archive.org/web/20111006173531/http://www.wyomingpaleo.org/references/Turner-Peterson_synthesis.pdf Synthesis]
- [http://search.datapages.com/data/specpubs/study46/ch14/images/ch14.pdf lacustrine carbonates]
Footnotes
{{Reflist|2}}
= Bibliography =
{{Commons category|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}}
Category:Sandstone formations of the United States