Aguja Formation

Aguja Formation Stratigraphic range: Campanian-Maastrichtian, 80.5–72 Ma PreЄ Є 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] Chihuahua, and Coahuila[7]		osteoderm and mandible fragment		Deinosuchus skull reconstruction.
Phobosuchus[6]	P. riograndensis[6]	Texas,[6] Chihuahua, and Coahuila			Reclassified as a Deinosuchus species.

Ornithischians

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.

Ornithischians of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Agujaceratops[8]	A. mariscalensis[8]	Texas[8]	Low Upper Shale[2]		The type species, A. mariscalensis, was formerly considered a species of Chasmosaurus.[8]	Agujaceratops
Angulomastacator[9]	A. daviesi[9]	Texas[9]
Chasmosaurus[10]	C. mariscalensis[11]	Texas[11]		"[Twelve] disarticulated skull (sic), postcrania, juvenile."[12]	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.[8]
	Indeterminate[13]	Chihuahua[13]
Edmontonia[11]	Unnamed species[14]	Texas[11]
cf. Euoplocephalus[11]	Unnamed species[11]	Texas[11]
Unnamed genus and species[15]		Texas[11]			Formerly referred to Kritosaurus and Gryposaurus, appears to be an unnamed species related to Secernosaurus.[16]
Kritosaurus[10]	Indeterminate[10]	Chihuahua[17]
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]

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.

Saurischians of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
cf. Daspletosaurus[19]	Indeterminate[19]	Texas[19]
cf. Dromaeosaurus[20]	Indeterminate[20]	Texas[11]
Leptorhynchos	L. gaddisi	Texas[21]			A caenagnathid.	Troodon
Ricardoestesia[22]	R. cf. gilmorei[23]	Texas[22]
	R. isosceles[22]	Texas[22]
Saurornitholestes[11]	S. cf. langstoni[24]	Texas[11]
cf. Troodon[25]	Indeterminate[25]	Texas[11]

Turtles

Testudines of the Aguja Formation
Genus	Species	Location	Member	Material	Notes
Terlinguachelys[6]	T. fischbecki[6]	Texas	Rattlesnake Mountain Sandstone[6]

See also

• List of dinosaur-bearing rock formations

Footnotes

1. Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. ISBN 0-520-24209-2.
2. Longrich, N. R.; Sankey, J.; Tanke, D. (2010). "Texacephale langstoni, a new genus of pachycephalosaurid (Dinosauria: Ornithischia) from the upper Campanian Aguja Formation, southern Texas, USA". Cretaceous Research 31 (2): 274. doi:10.1016/j.cretres.2009.12.002.
3. Woodward, H. N. (2005). Bone histology of the sauropod dinosaur Alamosaurus sanjuanensis from the Javelina Formation, Big Bend National Park, Texas.
4. Sankey, J. (2010). Faunal composition and significance of high–diversity, mixed bonebeds containing Agujaceratops mariscalensis and other dinosaurs, Aguja Formation (Upper Cretaceous), Big Bend, Texas. In New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium (pp. 520-537).
5. 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.
6. "Aguja Formation (Upper Shale Member), Big Bend Region, Texas," in Sullivan and Lucas (2006). Page 16.
7. "The first mandible fragment of Deinosuchus (Eusuchia: Alligatoroidea) discovered in Coahuila, Mexico". ResearchGate. Retrieved 2016-03-27.
8. "Abstract," Lucas, Sullivan, and Hunt. (2006).
9. Wagner and Lehman (2009).
10. "Dinosaur distribution (Texas and Chihuahua)." Weishampel, et al. (2004). Page 582 and 588.
11. "Dinosaur distribution (Late Cretaceous; North America; Texas)." Weishampel, et al. (2004). Page 582.
12. "Table 23.1," in Weishampel, et al. (2004). Page 496.
13. Listed as ?Chasmosaurus sp. in "Dinosaur distribution (Late Cretaceous; North America; Chihuahua)." Weishampel, et al. (2004). Page 588.
14. Listed as Edmontonia cf. rugosidens in "Dinosaur distribution (Late Cretaceous; North America; Texas)." Weishampel, et al. (2004). Page 582.
15. Listed as ?Gryposaurus sp. in "Dinosaur distribution (Late Cretaceous; North America; Texas)." Weishampel, et al. (2004). Page 582.
16. Prieto-Márquez, A. (2013). "Skeletal morphology of Kritosaurus navajovius (Dinosauria:Hadrosauridae) from the Late Cretaceous of the North American south-west, with an evaluation of the phylogenetic systematics and biogeography of Kritosaurini." Journal of Systematic Palaeontology, (advance online publication) doi:10.1080/14772019.2013.770417
17. "Dinosaur distribution (Late Cretaceous; North America; Chihuahua)." Weishampel, et al. (2004). Page 588.
18. "Abstract," Longrich, Sankey, and Tanke (2010).
19. Mortimer, M (2004). "Tyrannosauroidea". The Theropod Database. Retrieved 2007-08-21.
20. Listed as cf. Dromaeosaurus sp. in "Dinosaur distribution (Late Cretaceous; North America; Texas)." Weishampel, et al. (2004). Page 582.
21. Longrich, N. R.; Barnes, K.; Clark, S.; Millar, L. (2013). "Caenagnathidae from the Upper Campanian Aguja Formation of West Texas, and a Revision of the Caenagnathinae". Bulletin of the Peabody Museum of Natural History 54: 23. doi:10.3374/014.054.0102. edit
22. "Dinosaur distribution (Late Cretaceous; North America; Texas)." Weishampel, et al. (2004). Page 581.
23. Listed as R. cf. gilmorei in "Dinosaur distribution (Late Cretaceous; North America; Texas)." Weishampel, et al. (2004). Page 581.
24. Listed as Saurornitholestes cf. langstoni in "Dinosaur distribution (Late Cretaceous; North America; Texas)." Weishampel, et al. (2004). Page 582.
25. Listed as cf. Troodon sp. in "Dinosaur distribution (Late Cretaceous; North America; Texas)." Weishampel, et al. (2004). Page 582.

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.