# Popo Agie Formation

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Geologic formation in the United States

Popo Agie Formation Stratigraphic range: Late Triassic Carnian PreꞒ Ꞓ O S D C P T J K Pg N Type Geological formation Unit of Chugwater Group Overlies Gartra Formation Location Region North America Country United States

The **Popo Agie Formation** ([/poʊˈpoʊʒə/](https://en.wikipedia.org/wiki/Help:IPA/English) [*poh-POH-zhə*](https://en.wikipedia.org/wiki/Help:Pronunciation_respelling_key))[1][2] is a [Triassic](/source/Triassic) geologic [formation](/source/Formation_(geology)) that [crops out](/source/Outcrop) in western [Wyoming](/source/Wyoming), western [Colorado](/source/Colorado), and [Utah](/source/Utah). It was deposited during the [Late Triassic](/source/Late_Triassic) in [fluvial](/source/Fluvial) (river) and [lacustrine](/source/Lake) (lake) environments that existed across much of what is now the American southwest.[3] The earliest known [dinosaur](/source/Dinosaur) of the [Laurasian](/source/Laurasia) continent, *[Ahvaytum](/source/Ahvaytum)*, is discovered from the Popo Agie Formation. Dinosaurian trace fossils and fragmentary fossils of prehistoric reptiles and amphibians, including [pseudosuchian](/source/Pseudosuchian) reptiles and [temnospondyl](/source/Temnospondyl) amphibians, have also been reported from this formation.[4]

## Paleobiota

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.

### Amphibians

Taxon Species Member Material Notes Images Apachesaurus A. sp. Complete skull A metoposaurid temnospondyl, originally described as Anaschisma sp. and later Eupelor browni[5] Anaschisma A. browni Complete skull A metoposaurid temnospondyl[6] Metoposauridae Indeterminate Complete skull Originally described as Anaschisma browni[5]

### Reptiles

Taxon Species Member Material Notes Images Ahvaytum[4] A. bahndooiveche UWGM 1975, a left astragalus, and UWGM 7549, a partial left femur A probable sauropodomorph dinosaur and the oldest known Laurasian dinosaur Heptasuchus H. clarki UW 11562, a partial skull and postcranial skeleton; UW 11563 through UW 11565, partial postcranial remains; both from Big Horn Mountains, Wyoming[7] A rauisuchian (in background) Beesiiwo B. cooowuse USNM 494329, a left maxilla and left dentary from Hole in the Wall, Wyoming; TxVP 46037.1, UWGM 7027 and UWGM 7028, maxillary fragments from Cottonwood Creek, Wyoming[8] A rhynchosaur, previously assigned to cf. Hyperodapedon sanjuanensis (in foreground) Poposaurus P. gracilis UR 358, a partial ilium from Lander, Wyoming;[9] UR 357, a partial skeleton including vertebrae, hips, and limb bones[10] A bipedal poposauroid first described from the Popo Agie Formation and known from more complete specimens from the Chinle Formation[11] Sulcimentisauria indet.[4] Indeterminate A partial left humerus and right femur A 'silesaurid'

### Synapsids

Taxon Species Member Material Notes Images Eubrachiosaurus E. browni FMNH UC 633, a partial left scapula, left humerus, and left pelvis from Lander, Wyoming A dicynodont[12]

## See also

- [Earth sciences portal](https://en.wikipedia.org/wiki/Portal:Earth_sciences)
- [Paleontology portal](https://en.wikipedia.org/wiki/Portal:Paleontology)
- [Dinosaurs portal](https://en.wikipedia.org/wiki/Portal:Dinosaurs)

- [List of dinosaur-bearing rock formations](/source/List_of_dinosaur-bearing_rock_formations) - [List of stratigraphic units with indeterminate dinosaur fossils](/source/List_of_stratigraphic_units_with_indeterminate_dinosaur_fossils)

## Footnotes

1. **[^](#cite_ref-1)** Locally "po-PO-zha" according to Don Pitcher, 2006, *Moon Handbooks Wyoming,* p. 269 [\[1\]](https://books.google.com/books?id=nMG0xC1Y_eoC&pg=PA269&vq=Popo+Agie&source=gbs_search_r&cad=0_1)

1. **[^](#cite_ref-Popo_2-0)** More ambiguous transcription of "po-po-zsha" at ["Popo Agie Wilderness"](http://www.wilderness.net/index.cfm?fuse=NWPS&sec=wildView&WID=470). *The National Wilderness Preservation System*. Wilderness.net. Retrieved 2008-03-08.

1. **[^](#cite_ref-HHCP69_3-0)** High, L.R.; Hepp, D.M.; Clark, T.; Picard, M.D. (1969). "Stratigraphy of Popo Agie Formation (Late Triassic), Uinta Mountain Area, Utah and Colorado". *Geologic Guidebook of the Uinta Mountains: Utah's Maverick Range* (Sixteenth Annual Field Conference ed.). Utah Geological Association. pp. 181–192.

1. ^ [***a***](#cite_ref-Ahvaytum_4-0) [***b***](#cite_ref-Ahvaytum_4-1) [***c***](#cite_ref-Ahvaytum_4-2) Lovelace, David M; Kufner, Aaron M; Fitch, Adam J; Curry Rogers, Kristina; Schmitz, Mark; Schwartz, Darin M; LeClair-Diaz, Amanda; St.Clair, Lynette; Mann, Joshua; Teran, Reba (2025-01-01). "Rethinking dinosaur origins: oldest known equatorial dinosaur-bearing assemblage (mid-late Carnian Popo Agie FM, Wyoming, USA)". *Zoological Journal of the Linnean Society*. **203** (1) zlae153. [doi](/source/Doi_(identifier)):[10.1093/zoolinnean/zlae153](https://doi.org/10.1093%2Fzoolinnean%2Fzlae153). [ISSN](/source/ISSN_(identifier)) [0024-4082](https://search.worldcat.org/issn/0024-4082).

1. ^ [***a***](#cite_ref-ST02_5-0) [***b***](#cite_ref-ST02_5-1) Sulej, T. (2002). ["Species discrimination of the Late Triassic temnospondyl amphibian Metoposaurus diagnosticus"](https://www.app.pan.pl/archive/published/app47/app47-535.pdf) (PDF). *Acta Palaeontologica Polonica*. **47** (3): 535–546.

1. **[^](#cite_ref-6)** Gee, B. M.; Jasinski, S. E. (2021). "Description of the metoposaurid *Anaschisma browni* from the New Oxford Formation of Pennsylvania". *Journal of Paleontology*. **95** (5): 1061–1078. [Bibcode](/source/Bibcode_(identifier)):[2021JPal...95.1061G](https://ui.adsabs.harvard.edu/abs/2021JPal...95.1061G). [doi](/source/Doi_(identifier)):[10.1017/jpa.2021.30](https://doi.org/10.1017%2Fjpa.2021.30). [S2CID](/source/S2CID_(identifier)) [235546289](https://api.semanticscholar.org/CorpusID:235546289).

1. **[^](#cite_ref-DZC79_7-0)** Dawley, R.M.; Zawiskie, J.M.; Cosgriff, J.W. (1979). "A rauisuchid thecodont from the Upper Triassic Popo Agie Formation of Wyoming". *Journal of Paleontology*. **53** (6): 1428–1431.

1. **[^](#cite_ref-Fitch2023_8-0)** Fitch, A. J.; Haas, M.; C'Hair, W.; Ridgley, E.; Ridgley, B.; Oldman, D.; Reynolds, C.; Lovelace, D. M. (2023). ["A New Rhynchosaur Taxon from the Popo Agie Formation, WY: Implications for a Northern Pangean Early-Late Triassic (Carnian) Fauna"](https://doi.org/10.3390%2Fd15040544). *Diversity*. **15** (4): 544. [doi](/source/Doi_(identifier)):[10.3390/d15040544](https://doi.org/10.3390%2Fd15040544). [hdl](/source/Hdl_(identifier)):[10919/114487](https://hdl.handle.net/10919%2F114487).

1. **[^](#cite_ref-LJH07_9-0)** Lees, J.H. (1907). ["The skull of *Paleorhinus*, a Wyoming phytosaur"](https://zenodo.org/record/1431447). *The Journal of Geology*. **15** (2): 121–151. [Bibcode](/source/Bibcode_(identifier)):[1907JG.....15..121L](https://ui.adsabs.harvard.edu/abs/1907JG.....15..121L). [doi](/source/Doi_(identifier)):[10.1086/621382](https://doi.org/10.1086%2F621382). [JSTOR](/source/JSTOR_(identifier)) [30056366](https://www.jstor.org/stable/30056366). [S2CID](/source/S2CID_(identifier)) [129850970](https://api.semanticscholar.org/CorpusID:129850970).

1. **[^](#cite_ref-MMG15_10-0)** Mehl, M.G. (1915). ["*Poposaurus gracilis*, a new reptile from the Triassic of Wyoming"](https://zenodo.org/record/1431461). *The Journal of Geology*. **23** (6): 516–522. [Bibcode](/source/Bibcode_(identifier)):[1915JG.....23..516M](https://ui.adsabs.harvard.edu/abs/1915JG.....23..516M). [doi](/source/Doi_(identifier)):[10.1086/622268](https://doi.org/10.1086%2F622268). [JSTOR](/source/JSTOR_(identifier)) [30067173](https://www.jstor.org/stable/30067173).

1. **[^](#cite_ref-Getal11_11-0)** Gauthier, J.A.; Nesbitt, S.J.; Schachner, E.R.; Bever, G.S.; Joyce, W.G. (2011). ["The bipedal stem crocodilian *Poposaurus gracilis*: inferring function in fossils and innovation in archosaur locomotion"](https://web.archive.org/web/20150924021606/http://www.geo.uni-tuebingen.de/fileadmin/website/arbeitsbereich/palaeo/biogeologie/Images/Joyce_Publications/32__Gauthier_et_al.__Poposaurus__2011.pdf) (PDF). *Bulletin of the Peabody Museum of Natural History*. **52** (1): 107–126. [doi](/source/Doi_(identifier)):[10.3374/014.052.0102](https://doi.org/10.3374%2F014.052.0102). [S2CID](/source/S2CID_(identifier)) [86687464](https://api.semanticscholar.org/CorpusID:86687464). Archived from [the original](http://www.geo.uni-tuebingen.de/fileadmin/website/arbeitsbereich/palaeo/biogeologie/Images/Joyce_Publications/32__Gauthier_et_al.__Poposaurus__2011.pdf) (PDF) on 2015-09-24.

1. **[^](#cite_ref-KFA13_12-0)** Kammerer, C. F.; Fröbisch, J. R.; Angielczyk, K. D. (2013). Farke, Andrew A (ed.). ["On the Validity and Phylogenetic Position of Eubrachiosaurus browni, a Kannemeyeriiform Dicynodont (Anomodontia) from Triassic North America"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3669350). *PLOS ONE*. **8** (5) e64203. [Bibcode](/source/Bibcode_(identifier)):[2013PLoSO...864203K](https://ui.adsabs.harvard.edu/abs/2013PLoSO...864203K). [doi](/source/Doi_(identifier)):[10.1371/journal.pone.0064203](https://doi.org/10.1371%2Fjournal.pone.0064203). [PMC](/source/PMC_(identifier)) [3669350](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3669350). [PMID](/source/PMID_(identifier)) [23741307](https://pubmed.ncbi.nlm.nih.gov/23741307).

## References

- Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. [ISBN](/source/ISBN_(identifier)) [0-520-24209-2](https://en.wikipedia.org/wiki/Special:BookSources/0-520-24209-2).

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