Popo Agie Formation

Popo Agie Formation Stratigraphic range: Late Triassic
Type	Geological formation
Unit of	Chugwater Group
Overlies	Gartra Formation
Location
Region	North America
Country	United States

The Popo Agie Formation is a Triassic geologic formation that outcrops 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

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	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[3]
Metoposauridae indet.		Complete skull	Specimen was originally described as Anaschisma browni[3]

Reptiles

Taxon	Member	Material	Notes	Images
Heptasuchus 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
Hyperodapedon cf. H. sanjuanensis		USNM 494329, a left maxilla and premaxilla from Willow Creek, Wyoming[5]	A rhynchosaur
Poposaurus 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

Taxon	Member	Material	Notes	Images
Eubrachiosaurus browni		FMNH UC 633, a partial left scapula, left humerus, and left pelvis from Lander, Wyoming	One of only two dicynodonts known to have lived in the northern hemisphere during the Late Triassic, the other being Placerias from the Chinle Formation[9]

See also

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

Footnotes

1. 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.
2. Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
3. Sulej, T. (2002). "Species discrimination of the Late Triassic temnospondyl amphibian Metoposaurus diagnosticus" (PDF). Acta Palaeontologica Polonica. 47 (3): 535–546.
4. 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.
5. Lucas, S.G.; Heckert, A.B.; Hotton, N.III. (2002). "The rhynchosaur Hyperodapedon from the Upper Triassic of Wyoming and its global biochronological significance" (PDF). In Heckert, A.B.; and Lucas, S.G. (eds.). Upper Triassic Stratigraphy and Paleontology. 21. New Mexico Museum of Natural History and Science Bulletin. pp. 149–156.
6. Lees, J.H. (1907). "The skull of Paleorhinus, a Wyoming phytosaur". The Journal of Geology. 15 (2): 121–151. doi:10.1086/621382. JSTOR 30056366.
7. Mehl, M.G. (1915). "Poposaurus gracilis, a new reptile from the Triassic of Wyoming". The Journal of Geology. 23 (6): 516–522. doi:10.1086/622268. JSTOR view/30067173.
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" (PDF). Bulletin of the Peabody Museum of Natural History. 52 (1): 107–126. doi:10.3374/014.052.0102.
9. 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". PLoS ONE. 8 (5): e64203. doi:10.1371/journal.pone.0064203.

References

• Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.