Aguja Formation

Aguja Formation Stratigraphic range: Lower to Middle Campanian ~81.5–76.9 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Outcrops of the Aguja Formation, Big Bend National Park, Texas
Type	Geological formation
Unit of	Tornillo Group
Sub-units	Upper Shale, Terlingua Creek Sandstone, Rattlesnake Mt. Sandstone, Lower Shale & Basal Sandstone Members
Underlies	Javelina Formation
Overlies	Pen Formation
Lithology
Primary	Sandstone, conglomerate, claystone
Other	Mudstone, shale, limestone
Location
Coordinates	29°18′N 103°30′W / 29.3°N 103.5°W / 29.3; -103.5Coordinates: 29°18′N 103°30′W / 29.3°N 103.5°W / 29.3; -103.5
Approximate paleocoordinates	35°48′N 77°00′W / 35.8°N 77.0°W / 35.8; -77.0
Region	Texas  Chihuahua  Coahuila
Country	USA  Mexico
Aguja Formation (the United States) Aguja Formation (Texas) Show map of the United StatesShow map of TexasShow all

Paleogeography of the Campanian

The Aguja Formation is a geological formation in North America, exposed in Texas, United States and Chihuahua and Coahuila in Mexico, 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. Due to the presence of the ammonite Baculites mclearni, which only occurs from 80.67 - 80.21 Ma, in the underlying Rattlesnake Mountain Sandstone and the Terlingua Creek Sandstone, it is likely that the Upper Shale was younger than 80.2 Ma.^[2] A radiometric date of 76.9 Ma was recovered in the Upper Shale, making it likely the formation wasn't younger than 76.9 Ma.^[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] This is unlikely, however, due to the presence of Bravoceratops, more primitive than an unnamed chasmosaurine from the De-na-zin Member of the Kirtland Formation, in the lowermost section of the formation.^[5] The age of the Basal Sandstone is constrained by the presence of Scaphites hippocrepis III in the overlying Pen Formation which has been dated as old as 81.53 Ma.^[2][6]

Vertebrate paleofauna[]

A duckbilled dinosaur (Hadrosauridae) caudal vertebra from the Aguja Formation

Pseudosuchians[]

Crurotarsans of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Deinosuchus[7]	D. riograndensis[7]	Texas,[7] Chihuahua, and Coahuila[8]		osteoderm and mandible fragment
Phobosuchus[7]	P. riograndensis[7]	Texas,[7] Chihuahua, and Coahuila			Reclassified as a Deinosuchus species

Ornithischians[]

Ornithischians of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Agujaceratops[9]	A. mariscalensis[9]	Texas[9]	Low Upper Shale[10]		The type species, A. mariscalensis, was formerly considered a species of Chasmosaurus[9]
	A. mavericus[11]	Texas
Angulomastacator[12]	A. daviesi[12]	Texas[12]
Chasmosaurus[13]	C. mariscalensis[14]	Texas[14]		[Twelve] disarticulated skull (sic), postcrania, juvenile."[15]	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.[9]
Edmontonia[14]	E. sp[16][17]	Texas[14][17]
cf. Euoplocephalus[14]	E. sp[14][17]	Texas[14][17]
Panoplosaurus[18]	P. mirus[17]	Texas[17]
Aquilarhinus[19]	A. palimentus	Texas[14]			Formerly referred to Kritosaurus and Gryposaurus.[20]
Kritosaurus[13]	Indeterminate[13]	Chihuahua[21]
Texacephale[22]	T. langstoni[22]	Texas[22]	Low Upper Shale[10]
Yehuecauhceratops[23]	Y. mudei[24]	Coahuila[25]

Saurischians[]

Indeterminate ornithomimid remains are known from the Upper Aguja Formation.^[26] Indeterminate tyrannosaurid fossils are known from the Upper Aguja Formation of Texas and Mexico.^[27]

Saurischians of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
cf. Tyrannosauridae[27]	Indeterminate[27]	Texas[27]
cf. Dromaeosaurus[28]	Indeterminate[28]	Texas[14]
Leptorhynchos	L. gaddisi	Texas[29]			A caenagnathid
Ricardoestesia[30]	R. cf. gilmorei[31]	Texas[30]
	R. isosceles[30]	Texas[30]
Saurornitholestes[14]	S. cf. langstoni[32]	Texas[14]
cf. Troodon[33]	Indeterminate[33]	Texas[14]

Turtles[]

Invertebrates[]

Ammonites[]

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

See also[]

• List of dinosaur-bearing rock formations

References[]

Bibliography[]

• 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^{[permanent dead link]}." 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^{[permanent dead link]}
• 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. S2CID 128555861.
• Weishampel, David B.; Peter Dodson, and Halszka Osmólska (eds.). 2004. The Dinosauria, 2nd edition, 1–880. Berkeley: University of California Press. Accessed 2019-02-21. ISBN 0-520-24209-2