Aguja Formation

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] Fossil palms have also been unearthed here.^[2]

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	La Basa Sandstone Member, Rattlesnake Mountain Sandstone Member, Terlingua Creek Sandstone Member, Abajo Shale Member, and Alto Shale Member
Underlies	Javelina Formation
Overlies	Pen Formation
Lithology
Primary	Sandstone, conglomerate, claystone
Other	Mudstone, shale, limestone
Location
Coordinates	29.3°N 103.5°W / 29.3; -103.5
Approximate paleocoordinates	35.8°N 77.0°W / 35.8; -77.0
Region	Texas, Chihuahua, Coahuila
Country	United States, Mexico
Aguja Formation (the United States) Show map of the United States Aguja Formation (Texas) Show map of Texas

Paleogeography of the Campanian

Age

The ages of the Aguja Formation and its primary fossil-bearing unit, the Alto 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.^[3] A radiometric date of 76.9 Ma was recovered in the Alto Shale, making it likely the formation wasn't younger than 76.9 Ma.^[3] The contact with the overlying Javelina Formation has been estimated at 70 Ma ago^[4] but also as recently as 68.5 million years ago.^[5] 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.^[6] The age of the La Basa 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.^[3][7]

Paleofauna

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

Reptiles

2 fragmentary caudal vertebrae of indeterminate reptiles are known from the Rattlesnake Mountain sandstone member.^[8]

Ornithischians

Ornithischians of the Aguja Formation
Genus	Species	Location	Member[9]	Material	Notes	Images
Agujaceratops	A. mariscalensis	Texas[10]	Lower Alto Shale		Formerly considered a species of Chasmosaurus[10]
	A. mavericus	West Texas[11]	Middle Alto Shale		A chasmosaurine.
Angulomastacator	A. daviesi	Texas[12]	Middle Alto Shale	A left maxilla.[12]	A lambeosaurine.
Ankylosauridae	Indeterminate	Texas[13]	Lower Alto Shale	Osteoderms, vertebrae & limb elements.[13]	Remains of an ankylosaurid, possibly represents Euoplocephalus sp.[13]
Aquilarhinus[14]	A. palimentus	Texas[7]	Middle Abajo Shale	Partial skeleton	Formerly referred to Kritosaurus and Gryposaurus.[15]
Ceratopsidae genus & species indeterminate	Indeterminate	West Texas[16]	Middle Abajo Shale	Ilia, sacral vertebra & sacral ribs.[16]	May represent Agujaceratops, but undiagnostic.
Chasmosaurus[17]	C. mariscalensis[18]	Texas[18]		[Twelve] disarticulated skull (sic), postcrania, juvenile."[19]	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.[10]
Edmontonia	E. sp[20]	Texas[13]	Lower Alto Shale	Osteoderm (TVP 45866-2) & skull (AMNH 3076).[13]	A nodosaurid.
cf. Euoplocephalus[18]	E. sp[18]	Texas[13]	Lower Alto Shale	Osteoderms, sacrum & vertebra (TL-05-14).[13]	An ankylosaurid.
aff. Kritosaurus	K. navajovius	Texas[15]	Upper Alto Shale	Two dentary teeth	Tooth crown morphology matches with Kritosaurus[15]
Malefica	M. deckerti	Texas[21]	Middle Alto Shale	A partial left maxilla.[21]	Formerly referred to Kritosaurus.[21]
Nodosauridae genus & species indeterminate	Indeterminate	West Texas[16]	Middle Abajo Shale	Isolated & associated osteoderms.[16]	Very similar to osteoderms of Invictarx.
Panoplosaurus	P. mirus	Texas[13]	Lower Alto Shale	Osteoderm (TMM 45605-4).[13]	A nodosaurid.
Saurolophinae	Indeterminate	Texas[15]	Alto Shale	Various cranial and appendicular elements	Material from several localities previously referred to Kritosaurus but do not have its diagnostic features.[15]
Saurolophinae	Indeterminate	Texas	Alto Shale	Various manual elements and vertebrae representing two individuals	Included in phylogenetic analyses as the "Big Bend OTU", most recently considered a kritosaurin[21]
Stegoceras	S. sp.	West Texas[22]	Middle Alto Shale	Frontal[22]	A pachycephalosaur, represents a new unnamed species
Texacephale	T. langstoni	Texas[23]	Lower Alto Shale	Two frontoparietal domes.[23]	A pachycephalosaur.
Yehuecauhceratops	Y. mudei[24]	Coahuila[25]			A centrosaurine.

Theropods

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]

Theropods of the Aguja Formation
Genus	Species	Location	Member[9]	Material	Notes	Images
Avialae incertae sedis		West Texas[28]	Middle Abajo Shale[28]	4 teeth (TMM 45947-349, 350, 351).[28]	A bird.
Chirostenotes	C. sp.	Texas[29]		Femur & manual ungual.[29]	A caenagnathid
Dromaeosauridae genus & species indeterminate	Indeterminate	West Texas[16]	Middle Abajo Shale	Pedal phalanges (TMM 45909-2, TMM 44066-4).[16]	A dromaeosaur.
cf. Dromaeosaurus[30]	Indeterminate[30]	Texas[18]
Leptorhynchos	L. gaddisi	Texas[29]	Lower Alto Shale	Dentaries, caudal vertebra & limb elements.[29]	A caenagnathid
Ornithomimidae	New genus & species	West Texas[16]	Middle Abajo Shale	Vertebrae, ischium & limb elements.[16]	An unnamed species referred to informally as the 'Aguja ornithomimid'.
cf. Paronychodon		West Texas[28]	Middle Abajo Shale[28]	2 incomplete teeth (TMM 45947-362).[28]	A maniraptoran.
Richardoestesia	R. cf. gilmorei	Texas[31]	Low Upper Shale[31]	Fragment of a small tooth.[31]	A coelurosaur.
	R. isosceles	Big Bend National Park, Texas[31]	Low Upper Shale[31]	Teeth.[31]	A coelurosaur.
Saurornitholestes	S. cf. langstoni	Texas[28][31]	Lower Alto Shale & Middle Abajo Shale[28][31]	Teeth.[28][31]	A dromaeosaur, Teeth can belong to different taxa.
	S. langstoni	Coahuila [32]		Teeth [32]
	Saurornitholestes sp.	Coahuila [32]		Teeth [32]
Theropoda incertae sedis	Morphotype A	West Texas[28]	Alto Shale[28]	8 teeth.[28]	Unserrated, recurved teeth.
	Morphotype B	West Texas[28]		5 tooth crowns.[28]	Bi-serrated teeth.
	Morphotype C	West Texas[28]		7 teeth.[28]	Finely serrated, distal plication only.
	Morphotype D	West Texas[28]		5 teeth.[28]	Short, coarsely serrated distal plication.
	Morphotype E	West Texas[28]		A tooth.[28]	Strongly recurved, serrated distal plication.
	Morphotype F	West Texas[28]		2 tooth fragments.[28]	Medium size, finely serrated plications.
cf. Troodon[33]	Indeterminate[33]	Texas[18]
Tyrannosauridae	Indeterminate	West Texas[28][34]	Lower Alto Shale[34] & Middle Abajo Shale[16][28]	Isolated teeth & a handful of non-dental specimens.[28][34]	Postcranial remains suggest a relatively small & gracile tyrannosaurid,[34] considered a member of the Teratophoneini[35]

Sauropods

Indeterminate titanosaurid remains are known from the Upper Aguja Formation of Mexico.^[36]

Sauropods of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Titanosauridae	Indeterminate	Chihuahua		Four partial posterior caudal vertebrae & dorsal or sacrocaudal vertebra	A relatively massive titanosaurid.

Crocodylomorphs

Crocodylomorphs of the Aguja Formation
Genus	Species	Location	Member[9]	Material	Notes	Images
Crocodilia	Indeterminate	Ten Bits Ranch, west Texas.[8]	Rattlesnake Mountain sandstone member.[8]	Teeth.[8]	A crocodilian.
Deinosuchus[37]	D. riograndensis	Texas,[37] Chihuahua, and Coahuila[38]	Upper Shale	Multiple partial skulls & skeletons accounting for nearly the entire skeleton minus the tail.	A giant alligatoroid.
	cf. D. sp.	West Texas[16]	Middle Abajo Shale[16]	Cervical osteoderm (TMM 44068-2).[16]	An alligatoroid.
Goniopholididae	New genus & species	West Texas[16]	Middle Abajo Shale[16]	Partial skull & skeleton along with isolated osteoderms & teeth.[16]	May pertain to Denazinosuchus or a related taxon.
Phobosuchus[37]	P. riograndensis[37]	Texas,[37] Chihuahua, and Coahuila			Reclassified as a Deinosuchus species

Turtles

Testudines of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Adocus	A. sp.	Big Bend National Park, Texas.[39]	Upper Shale[39]	Shell fragments.[39]	An adocid.
cf. Aspideretoides		Big Bend National Park, Texas	Upper Shale		A softshell turtle
Baenidae		Big Bend National Park, Texas.[39]	Upper Shale[39]	Shell fragments.[39]	2 morphotypes present (A & B).
Basilemys	B. sp.	Big Bend National Park, Texas.[39]	Upper Shale & Lower Shale[16][39]	Shell fragments, partial plastron & leg scutes.[16][39]	A nanhsiungchelyid.
Bothremydidae genus & species indeterminate	Indeterminate	West Texas[16]	Lower Shale[16]	Isolated peripheral bones (TMM 44068-1, 42452-8); costal bones (TMM 44064-6).[16]	A bothremydid, compatible with Chupacabrachelys.
Chupacabrachelys	C. complexus	Big Bend, Texas.[40]	Base of the Upper Shale[40]	A complete skull, and a nearly complete skeleton.[40]	A bothremydid.
Denazinemys	D. nodosa	West Texas[16][41]	Lower Shale[16]	Shell elements.[16]	A baenid.
cf. Helopanoplia		Big Bend National Park, Texas.[39]	Upper Shale[39]	Shell fragments.[39]	A softshell turtle.
cf. Hoplochelys		Big Bend National Park, Texas.[39]	Upper Shale[39]	Shell fragments.[39]	A kinosternoid.
Neurankylus	N. baueri	West Texas	Lower Shale		A baenid
Terlinguachelys	T. fischbecki	Big Bend National Park, Texas[42]	Rattlesnake Mountain Sandstone[42]	A large, incomplete specimen.[42]	A protostegid.
Thescelus	T. rapiens	West Texas	Lower Shale		A baenid
Testudines indeterminate[8]	Morphotype 1[8]	Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	A shell fragment.
	Morphotype 2[8]	Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	A shell fragment.
	Morphotype 3[8]	Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	A shell fragment.
	Morphotype 4[8]	Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	A shell fragment.
Trionychidae	Gen. et. sp. indet.	Big Bend National Park, Texas.[39]	Upper Shale & Lower Shale[16][39]	Costal bone (TMM 44068-4) & shell fragments.[39]	A softshell turtle.

Lepidosaurs

Lepidosaurs of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Anguidae	Gen. et. sp. indet.	Texas.[43]		Isolated osteoderms & partial right frontal.[43]	An anguid.
Apsgnathus	A. triptodon	Brewster County, Texas.[43]		Jaw elements.[43]	A scincomorph.
Catactegenys	C. solaster	Brewster County, Texas.[43]		Jaw elements & teeth.[43]	A night lizard.
Dryadissector	D. shilleri	West Texas.[28]	Middle Abajo Shale	Numerous isolated teeth.[28]	A varanoid.
Mosasauridae	Indeterminate	Ten Bits Ranch.[8]	Rattlesnake Mountain sandstone member.[8]	1 partial vertebra.[8]	A mosasaur.
Odaxosaurus	O. piger	Brewster County, Texas.[43]		Jaw elements.[43]	An anguid.
cf. Parasaniwa	cf. P. wyomingensis	Texas.[43]		Jaw fragments.[43]	A platynotan.
Platynota	Gen. et. sp. indet.	Texas.[43]		Dorsal vertebra (TMM 43057-332).[43]	A platynotan.
?Scincidae	Gen. et. sp. indet.	Brewster County, Texas.[43]		Jaw elements.[43]	A possible skink.
cf. Scincomorpha	Gen. et. sp. indet.	Brewster County, Texas.[43]		Jaw elements.[43]	A scincomorph.
Serpentes	Gen. et. sp. indet.	Texas.[43]		Partial left dentary & right maxilla.[43]	A snake.
cf. Xenosauridae		Texas.[43]		Osteoderms & maxillae.[43]	A knob-scaled lizard.

Mammals

Mammals of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Alphadon[44]	A. perexiguus	Brewster County, Texas	Upper Shale		A metatherian.
Paleomolops[44]	P. langstoni	Brewster County, Texas	Upper Shale		A tribosphenidan; "cannot be confidently allied with either marsupials or eutherians".[44]

Bony fish

A diversity of bony fish, comprising both marine (Ten Bits/Rattlesnake Mountain locality) and freshwater (Lowerverse/Lower Shale locality) taxa, is known.^[45] Approximately 75 whole and broken fragments of coprolites are known from the Rattlesnake Mountain sandstone member, presumably from bony fish.^[8]

Bony fish of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Acanthomorpha indet.	family indet. genus et sp. indet.	Lowerverse, west Texas[45]	Lower Shale	Vertebral centra.	An acanthomorph.
Acanthopterygii indet.	order indet. family indet. genus et sp. indet.	Lowerverse, west Texas[45]	Lower Shale	Vertebral centra.	An acanthopterygian.
	Acanthopterygian fin spine morph 1			Fin spines
	Acanthopterygian fin spine morph 2
	Acanthopterygian fin spine morph 3
	Acanthopterygian fin spine morph 4
	Euacanthopterygian fin spine morph 1
	Euacanthopterygian fin spine morph 2
Albula	A. sp.	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	Over 390 complete and fragmentary teeth.[46]	A bonefish.
		Lowerverse, west Texas[45]	Lower Shale
Amiidae indet.	genus et sp. indet.	Lowerverse, west Texas[45]	Lower Shale	Vertebral centra.	An amiid.
?Anomoeodus	?A. sp.	Lowerverse, west Texas[45]	Lower Shale	Isolated tooth crown	A pycnodont. Likely transported out of a marine habitat.
Atractosteus	A. sp.	Lowerverse, west Texas[45]	Lower Shale	Teeth, jaw fragments, vertebral centra, scales.	A gar.
Clupeiformes indet.	family indet. genus et sp. indet.	Lowerverse, west Texas[45]	Lower Shale	Vertebral centra.	A clupeiform.
cf. Cyclurus	cf. C. sp.	Lowerverse, west Texas[45]	Lower Shale	5 fragmentary tooth plates with teeth.	An amiid.
Ellimmichthyiformes indet.	family indet. genus et sp. indet.	Lowerverse, west Texas[45]	Lower Shale	Vertebral centra.	An ellimmichthyiform.
Elopiformes indet.	family indet. genus et sp. indet.	Lowerverse, west Texas[45]	Lower Shale	Vertebral centra	An elopiform.
?Enchodus	?E. sp.	Ten Bits ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	2 abraded teeth.[46]	An aulopiform.
		Lowerverse, west Texas[45]	Lower Shale	4 isolated teeth.[45]
Eotexachara	E. malateres	Lowerverse, west Texas[47]	Lower Shale	Dentaries.[47]	A characiform.
?Gonorynchiformes indet.	family indet. genus et sp. indet.	Lowerverse, west Texas[47]	Lower Shale	Cranial bone, vertebral centrum, basibranchial.	A gonorynchiform.
Hiodontidae indet.	genus et sp. indet.	Lowerverse, west Texas[47]	Lower Shale	Vertebral centra.	A hiodontiform.
Lepidotes	?L. sp.	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	Approximately 109 complete and fragmentary teeth.[46]	A lepidotid.
cf. Melvius	cf. M. sp.	Lowerverse, west Texas[16][45]	Lower Shale[16]	Vertebrae, 13 isolated teeth.[16][45]	An amiid.
Micropycnodon	M. sp.	Lowerverse, west Texas[45]	Lower Shale	4 isolated teeth	A pycnodont. Likely transported out of a marine habitat.
Osteichthyes indet.	Indeterminate species A	Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	11 complete teeth.	A bony fish.
	Indeterminate species B			8 complete and fragmentary teeth.
	Indeterminate species C			1 complete tooth.
	Indeterminate species D			1 complete and 1 partial tooth.
	Indeterminate			Approximately 475 complete and fragmentary teleost centra.[46]
	Tooth morph 1	Lowerverse, west Texas[45]	Lower Shale	Teeth
	Tooth morph 2
	Centrum morph 1			Vertebral centra.
	Centrum morph 2
	Centrum morph 3
	Centrum morph 4
Ostariophysi indet.	order indet. family indet. genus et sp. indet.	Lowerverse, west Texas[45]	Lower Shale	Vertebral centra.	An ostariophysian.
Paralbula	P. cf. casei	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	Approximately 900 complete and fragmentary teeth and tooth caps.[46]	A bonefish. Lowerverse specimens likely transported out of a marine habitat.
		Lowerverse, west Texas[45]	Lower Shale
Primuluchara	P. laramidensis	Lowerverse, west Texas[47]	Lower Shale	Dentaries.[47]	A characiform.
Stephanodus	?S. sp.	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	21 whole and fragmentary specimens.[46]	A pycnodont.
?Wilsonichthys	?W. sp.	Lowerverse, west Texas[45]	Lower Shale	Vertebral centra.	An osteoglossiform.

Cartilaginous fish

Cartilaginous fish of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Brachyrhyzodus	B. wichitaensis	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	11 complete teeth.[46]
Cantioscyllium	C. aff. meyeri	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	1 anterior tooth and 5 lateral teeth.[8]	A nurse shark.
Chiloscyllium	C. aff. greeni	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8]	Approximately 90 abraded and fragmentary teeth.[46]	A bamboo shark.
Chondrichthyes[8]		Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	23 placoid scales and 69 dermal scales.	4 morphotypes of placoid scales (A to D) present.
Columbusia	C. sp.	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	20 complete & fragmentary teeth.[46]	A wobbegong.
Cretalamna	C. appendiculata	Ten Bits Ranch, west Texas.[8]	Rattlesnake Mountain sandstone member.[8]	3 fragmentary teeth.[8]	Reassigned to C. cf. C. sarcoportheta.[46]
	C. cf. C. sarcoportheta	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	3 incomplete teeth & fragments of additional teeth.[46]	Originally reported as C. appendiculata.
Cretorectolobus[8]	C. olsoni	Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	"20 complete and fragmentary teeth".	A carpet shark.
Hybodontidae genus & species indeterminate	Indeterminate	West Texas[16]	Lower Shale[16]	Fragment of a dorsal fin spine (TMM 42536-10).[16]	A hybodont.
Hybodus[8]	H. sp.	Ten Bits Ranch.	Rattlesnake Mountain sandstone member.[8]	2 specimens, one complete and one partial tooth.	A hybodont.
Igdabatis	I. indicus?	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	A single incomplete tooth.[8][46]	A myliobatid.
Ischyrhiza	I. cf. avonicola	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	5 complete and fragmentary rostral teeth.[46]	A sawskate.
	I. mira	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	11 fragmentary rostral teeth and 230 whole and fragmentary oral teeth.[46]	A sawskate.
Lonchidion[48]	L. conrugis	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	4 complete and 5 fragmentary teeth.[8][46]	A hybodont.
	L. selachos	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	4 complete and 5 fragmentary teeth.[8][46]	A hybodont.
Meristodon	M. sp.	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	2 teeth.[46]	A hybodont.
Myliobatiformes	Incertae sedis	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	3 complete specimens.[46]
Protoplatyrhina	P. renae	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8]	70 complete and fragmentary teeth.[46]	A hypsobatid.
Ptychotrygon	P. agujaensis	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	Over 690 complete and fragmentary teeth.[46]	A sawskate.
	P. triangularis	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	Over 170 complete and fragmentary teeth.[46]	A sawskate.
	P. aff. cuspidata	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	7 whole and fragmentary teeth.[46]	A sawskate.
	P. sp.	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	One complete tooth (TMM 46018-71).[46]	A sawskate.
Restesia[48]	R. corricki	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	4 complete and 5 fragmentary teeth.[8][46]	A carpet shark.
Rhinobatos	R. casieri	Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	"14 complete and fragmentary specimens".	A guitarfish.
	R. sp.	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	18 complete & fragmentary specimens.[46]	A guitarfish.
Rhombodus	R. levis	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	Over 22 complete and fragmentary teeth.[46]	A rajiforme.
Scapanorhynchus	S. texanus	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	Over 800 complete and fragmentary teeth.[46]	A mitsukurinid.
Sclerorhynchidae	Morphotype 1	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[8]	One fragmentary rostral spine (TMM 46018-59).[46]	A sawskate.
	Morphotype 2	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[8]	One fragmentary rostral spine (TMM 46018-60).[46]	A sawskate.
	Morphotype 3	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[8]	3 fragmentary rostral teeth.[46]	A sawskate.
	Morphotype 4	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[8]	27 fragmentary rostral spines.[46]	A sawskate.
Serratolamna	S. cf. S. caraibaea	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	About 34 teeth.[46]	A mackerel shark.
Squalicorax	S. kaupi	Ten Bits Ranch, west Texas.[8][46]	Rattlesnake Mountain sandstone member.[8][46]	"26 complete and fragmentary anterior and lateral teeth".	An anacoracid.
	S. aff. S. lindstromi	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	4 specimens.[46]	An anacoracid.
	S. pristodontus	Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	2 specimens.	An anacoracid.
	S. aff. S. yangaensis	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	4 complete & several fragmentary teeth.[46]	An anacoracid.
Squatina	S. hassei	Ten Bits Ranch, west Texas.[8]	Rattlesnake Mountain sandstone member.[8]	A single complete specimen.	An angelshark.
	S. sp.	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	A complete tooth & 2 fragmentary teeth.[46]	An angelshark.
Texatrygon	T. cf. T. copei	Ten Bits Ranch, west Texas.[46]	Rattlesnake Mountain sandstone member.[46]	4 complete & fragmentary teeth.[46]	A sawskate formerly reported as T. hooveri.
	T. hooveri	Ten Bits Ranch, west Texas.	Rattlesnake Mountain sandstone member.[8]	4 complete and fragmentary specimens.[8]	Reassigned to T. cf. T. copei.

Invertebrates

Ammonites

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

Plants

Plants of the Aguja Formation
Genus	Species	Location	Member	Material	Notes	Images
Sabal[2]	S. bigbendense	Big Bend National Park, Texas.	Upper Shale	4 seeds.	A palm. It has the largest seeds of any fossil Sabal.[2]
	S. bracknellense	Big Bend National Park, Texas.	Upper Shale	5 seeds.	A palm. The seeds are indistinguishable from those of Eocene S. bracknellense, and so were assigned to that species. However, it is likely these Aguja palms would be found to represent distinct species if other parts of the plants were available for comparison.[2]

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.

See also

• List of dinosaur-bearing rock formations