Popo Agie Formation Explained

Popo Agie Formation
Type:	Geological formation
Age:	Late Triassic
Period:	Norian
Region:	North America
Country:	United States
Unitof:	Chugwater Group
Overlies:	Gartra Formation

The Popo Agie Formation is a Triassic geologic formation that crops out in western Wyoming, western Colorado, and Utah. It was deposited during the Late Triassic in fluvial (river) and lacustrine (lake) environments that existed across much of what is now the American southwest.^[1] Fragmentary fossils of prehistoric reptiles and amphibians, including pseudosuchian reptiles and temnospondyl amphibians, have been discovered in the Popo Agie Formation. Dinosaur remains are also among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.^[2]

Paleobiota

Amphibians

Taxon	Member	Material	Notes	Images
Apachesaurus sp.		Complete skull	A metoposaurid temnospondyl; specimen from the Popo Agie Formation was originally described as Anaschisma sp. and later Eupelor browni^[3]
Koskinonodon perfecta		Complete skull	A metoposaurid temnospondyl; specimen from the Popo Agie Formation was originally described as Borborophagus wyomingensis
Metoposauridae indet.		Complete skull	Specimen was originally described as Anaschisma browni

Reptiles

Taxon	Species	Member	Material	Notes	Images
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^[4]	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^[5]	A rhynchosaur, previously assigned to cf. Hyperodapedon sanjuanensis	(in foreground)
Poposaurus	P. gracilis		UR 358, a partial ilium from Lander, Wyoming;^[6] UR 357, a partial skeleton including vertebrae, hips, and limb bones^[7]	A bipedal poposauroid first described from the Popo Agie Formation and known from more complete specimens from the Chinle Formation^[8]

Synapsids

See also

• List of dinosaur-bearing rock formations
  • List of stratigraphic units with indeterminate dinosaur fossils

References

• Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. .

Notes and References

1. Book: High, L.R.. Geologic Guidebook of the Uinta Mountains: Utah's Maverick Range. 1969. Utah Geological Association. 181–192. Sixteenth Annual Field Conference. Hepp, D.M. . Clark, T. . Picard, M.D. . Stratigraphy of Popo Agie Formation (Late Triassic), Uinta Mountain Area, Utah and Colorado.
2. Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
3. Sulej. T.. Species discrimination of the Late Triassic temnospondyl amphibian Metoposaurus diagnosticus. Acta Palaeontologica Polonica. 2002. 47. 3. 535–546.
4. Dawley. R.M.. Zawiskie, J.M. . Cosgriff, J.W. . A rauisuchid thecodont from the Upper Triassic Popo Agie Formation of Wyoming. Journal of Paleontology. 1979. 53. 6. 1428–1431.
5. Fitch . A. J. . Haas . M. . C’Hair . W. . Ridgley . E. . Ridgley . B. . Oldman . D. . Reynolds . C. . Lovelace . D. M. . A New Rhynchosaur Taxon from the Popo Agie Formation, WY: Implications for a Northern Pangean Early-Late Triassic (Carnian) Fauna . Diversity . 2023 . 15 . 4 . 544 . 10.3390/d15040544. 10919/114487 . free . free .
6. Lees . J.H. . 1907 . The skull of Paleorhinus, a Wyoming phytosaur . The Journal of Geology . 15 . 2 . 121–151 . 30056366 . 10.1086/621382 . 1907JG.....15..121L. 129850970 .
7. Mehl . M.G. . 1915 . Poposaurus gracilis, a new reptile from the Triassic of Wyoming . The Journal of Geology . 23 . 6 . 516–522 . 30067173 . 10.1086/622268 . 1915JG.....23..516M. free .
8. 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 . Bulletin of the Peabody Museum of Natural History . 52 . 1 . 107–126 . 10.3374/014.052.0102 . 86687464 . dead . 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 . 2015-09-24 .
9. Kammerer . C. F. . Fröbisch . J. R. . Angielczyk . K. D. . Farke . Andrew A . On the Validity and Phylogenetic Position of Eubrachiosaurus browni, a Kannemeyeriiform Dicynodont (Anomodontia) from Triassic North America . 10.1371/journal.pone.0064203 . PLOS ONE . 8 . 5 . e64203 . 2013 . 23741307. 3669350. 2013PLoSO...864203K . free .