Javelina Formation

The typical age range of the Javelina Formation has been difficult to determine.^[4] In 2006, the middle portion of the Javenila Formation about 90 meters (300 ft) below the K-Pg boundary was dated to 69.0±0.9 million years ago by Lehman and colleagues. Using this date, in correlation with a measured age from the underlying Aguja Formation and the likely location of the K-Pg boundary in the overlying Black Peaks Formation, the authors argued that the Alamosaurus fauna seems to have lasted from about 70–66 million years ago, with the earliest records of Alamosaurus near the base of the Javelina Formation and the latest just below the K-Pg boundary in the Black Peaks Formation.^[2] However, Leslie et al. (2018) and Lehman et al. (2022) later corrected this age estimate, since the dinosaur fossils are actually known from the upper portion of the Javelina Formation. The K-Pg boundary of the Javelina Formation is known to be at the ~172 meters (564 ft) level, and the youngest-known Alamosaurus fossil-bearing locality (TxVP 42426, incorrectly referred to TMM 41450 by Leslie et al. and subsequently corrected by Lehman et al.) is known from the top of the sandstone unit at ~145 meters (476 ft) level, approximately ~27 meters (89 ft) below the K-Pg boundary. With dating based on magnetostratigraphy constraining the maximum depositional age of the dinosaur fossil-bearing section at approximately 66.4 million years ago, the Alamosaurus fauna can be dated to the latest Maastrichtian age.^[5][6]

Vertebrates of the Javelina Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Bravoceratops	B. polyphemus				A chasmosaurine ceratopsid known from the lowermost part of the Javelina Formation which dates back to the early Maastrichtian.[10]
Chasmosaurinae indet.[7]	Indeterminate		Lower and Upper[7]	Dentary and horncore[7]	Multiple remains of indeterminate chasmosaurines. The horncore and dentary are stated as being similar in size to Triceratops.[7] The horncore comes from the Lower Javelina Formation and the dentary comes from the Upper Javelina Formation.[7]
Torosaurus[7]	T. cf. utahensis[7]				A chasmosaurine ceratopsid whose remains have been found in the Frenchman Formation, Hell Creek Formation, North Horn Formation, McRae Formation, and Lance Formation.
Ceratopsidae indet.	Indeterminate		Uppermost	Syncervical[5]	A large indeterminate ceratopsid, only diagnostic to Ceratopsidae.[7]

Hadrosaurs of the Javelina Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Gryposaurus?[11]	G.? alsatei[11]		Upper		A saurolophine hadrosaurid known from the Two Medicine Formation, the Dinosaur Park Formation, the Kaiparowits Formation, possible remains have also been unearthed in the El Picacho Formation.[12]
Kritosaurus[11][13][14][15]	K. cf. navajovius[11][13][15][14]				A saurolophine hadrosaurid, also known from the Kirtland Formation, Aguja Formation, Ojo Alamo Formation and the El Picacho Formation. A possible second species of Kritosaurus might have lived in the Javelina Formation.[11][15] Fossils have also been unearthed in the Olmos Formation.[16]
Saurolophinae indet.[11]	Indeterminate[11]				A saurolophine handrosaurid similar to the genus Saurolophus.

Sauropods of the Javelina Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Alamosaurus	A. sanjuanensis		Upper		A titanosaurian sauropod, also from the Ojo Alamo Formation

Theropods of the Javelina Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Ornithomimidae indet.[7]	Indeterminate		Upper		Fragmentary remains of an unnamed ornithomimid[17]
Saurornitholestes[18]	S. cf. langstoni				A dromaeosaurid
Troodontidae indet.	Indeterminate[19]				A troodontid
cf. Tyrannosaurus	Indeterminate[20]		Middle & Upper		A tyrannosaurid, originally identified from the Hell Creek Formation. Also found in the Denver, Ferris, Frenchman, Lance, Livingston, North Horn, Scollard, and Willow Creek Formations.[21]
Tyrannosauridae Indet.	Indeterminate		Upper	Hindlimb and metatarsal material.	Estimated as 75% the size of Sue the T. rex.[22] Possibly a sub-adult Tyrannosaurus or Small bodied taxon.

Pterosaurs of the Javelina Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Quetzalcoatlus	Q. northropi[23]		Upper		An azhdarchid pterosaur
	Q. lawsoni
Wellnhopterus[23]	W. brevirostris				An azhdarchid pterosaur

Fish of the Javelina Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Dasyatis[24]	Unknown				A ray
Rhombodus[24]	Unknown				A ray

Woody dicots and angiosperms have been unearthed in this formation.^[25][26] Plant fossils indicate that this area was a woodland habitat.^[26]