Aguja Formation

Aguja Formation Stratigraphic range: Campanian-Maastrichtian, 80.5–72Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Tornillo Group
Sub-units	Upper Shale Member Terlingua Creek Sandstone Member McKinney Springs Marine Tongue Rattlesnake Mt. Sandstone Member Lower Shale Member Basal Sandstone Member
Underlies	Javelina Formation
Overlies	Pen Formation
Location
Region	Texas  Chihuahua
Country	USA  Mexico

The Aguja Formation is a geological formation in North America, exposed in Texas, whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.^[1]

Age

The ages of the Aguja Formation and its primary fossil-bearing unit, the Upper Shale, are not well understood. Two radiometric dates have been taken from different sections of the upper shale, yielding ages of 72.6 Ma +/- 1.5 Ma old, and 76.9 Ma +/- 1.2 Ma old, respectively.^[2] The contact with the overlying Javelina Formation has been estimated at about 70 Ma ago^[3] but also as recently as 68.5 million years ago.^[4] The base of the entire Aguja Formation has been estimated at about 80.5 million years old.^[5]

Invertebrate paleofauna

Ammonites

Ammonites of the Aguja Formation
Genus	Species	Location	Member	Abundance	Notes	Images
Baculites	B. mclearni		Rattlesnake Mountain Sandstone			Pachydiscus
Hoplitoplacenticeras	H. plasticum		Rattlesnake Mountain Sandstone
Pachydiscus	P. paulsoni		Rattlesnake Mountain Sandstone

Vertebrate paleofauna

Crurotarsans

Crurotarsans of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Deinosuchus[6]	D. riograndensis[6]	Texas[6]				Deinosuchus skull reconstruction.
Phobosuchus[6]	P. riograndensis[6]	Texas[6]			Reclassified as a Deinosuchus species.

Ornithischians

Ornithischians of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Agujaceratops[7]	A. mariscalensis[7]	Texas[7]	Low Upper Shale[2]		The type species, A. mariscalensis, was formerly considered a species of Chasmosaurus.[7]	Agujaceratops
Angulomastacator[8]	A. daviesi[8]	Texas[8]
Chasmosaurus[9]	C. mariscalensis[10]	Texas[10]		"[Twelve] disarticulated skull (sic), postcrania, juvenile."[11]	Considered by paleontologists Lucas, Sullivan, and Hunt to be distinct enough from the Chasmosaurus type species, C. belli to warrant being split off to a new genus, Agujaceratops.[7]
	Indeterminate[12]	Chihuahua[12]
Edmontonia[10]	E. rugosidens[13]	Texas[10]
Euoplocephalus[10]	Unnamed species[10]	Texas[10]
Unnamed genus and species[14]		Texas[10]			Formerly referred to Kritosaurus and Gryposaurus, appears to be an unnamed species related to Secernosaurus.[15]
Kritosaurus[9]	K. cf. navajovius[16]	Texas[10]
	Indeterminate[9]	Chihuahua[17]
Panoplosaurus[10]	Unnamed species[10]	Texas[10]
Stegoceras[10]	Indeterminate[10]	Texas[10]
Texacephale[18]	T. langstoni[18]	Texas[18]	Low Upper Shale[2]

Saurischians

Indeterminate ornithomimid remains are known from the Upper Aguja Formation.^[5] Indeterminate tyrannosaurid fossils are known from the Upper Aguja Formation of Texas and Mexico.^[19]

Saurischians of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
cf. Daspletosaurus[20]	Indeterminate[21]	Texas[22]
cf. Dromaeosaurus[23]	Indeterminate[23]	Texas[10]
Leptorhynchos	L. gaddisi	Texas[24]			A caenagnathid.	Troodon
Ricardoestesia[25]	R. cf. gilmorei[26]	Texas[25]
	R. isosceles[25]	Texas[25]
Saurornitholestes[10]	S. cf. langstoni[27]	Texas[10]
cf. Troodon[28]	Indeterminate[28]	Texas[10]

Turtles

See also

• List of dinosaur-bearing rock formations

Footnotes

References

• Lehman, Thomas M.; Susan L. Tomlinson (2004). "Terlinguachelys fischbecki, a new genus and species of sea turtle (Chelonioidea: Protostegidae) from the Upper Cretaceous of Texas". Journal of Paleontology (The Paleontological Society) 78 (6): 1163–1178. doi:10.1666/0022-3360(2004)078<1163:TFANGA>2.0.CO;2. 
• Longrich, N.R., Sankey, J., and Tanke, D. (2010) Texacephale langstoni, a new genus of pachycephalosaurid (Dinosauria: Ornithischia) from the upper Campanian Aguja Formation, southern Texas, USA. Cretaceous Research. doi:10.1016/j.cretres.2009.12.002.
• Sullivan, R.M., and Lucas, S.G. 2006. "The Kirtlandian land-vertebrate "age" – faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of western North America." New Mexico Museum of Natural History and Science, Bulletin 35:7-29.
• Spencer G. Lucas, Robert M. Sullivan and Adrian P. Hunt: Re-evaluation of Pentaceratops and Chasmosaurus (Ornithischia: Ceratopsidae) in the Upper Cretaceous of the Western Interior. In: New Mexico Museum of Natural History and Science Bulletin 35 (2006), S. 367-370.PDF
• Wagner, Jonathan R.; Lehman, Thomas M. (2009). "An Enigmatic New Lambeosaurine Hadrosaur (Reptilia: Dinosauria) from the Upper Shale Member of the Campanian Aguja Formation of Trans-Pecos Texas". Journal of Vertebrate Paleontology 29 (2): 605–611. doi:10.1671/039.029.0208. 
• Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd ed., Berkeley: University of California Press. ISBN 0-520-24209-2.