Cerro del Pueblo Formation

The Cerro del Pueblo Formation is a geological formation in Saltillo, capital city of the state of Coahuila, Mexico, whose strata date back to the latest Campanian of the Late Cretaceous, just before the Campanian-Maastrichtian boundary. Dinosaur remains are among the fossils that have been recovered from the formation.^[1] The formation is believed to correlate with the Baculites reesidesi and Baculites jenseni ammonite zones, which dates it to 73.63-72.74 Ma.^[2]

Fragments of a hadrosaur skeleton weathering out of the Cerro del Pueblo Formation near Rincon Colorado, Coahuila

Cerro del Pueblo Formation
Stratigraphic range: Campanian ~73.6–72.7 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Difunta Group
Underlies	Cerro Huerta Formation
Overlies	Parras Shale
Thickness	160 m (520 ft)
Lithology
Primary	Mudstone, sandstone
Other	Siltstone, conglomerate, limestone
Location
Coordinates	26.1°N 101.1°W / 26.1; -101.1
Approximate paleocoordinates	32.2°N 75.5°W / 32.2; -75.5
Region	Coahuila
Country	Mexico
Extent	Parras Basin
Cerro del Pueblo Formation (Mexico) Show map of Mexico Cerro del Pueblo Formation (Coahuila) Show map of Coahuila

Paleogeography of the Campanian

Outcrops of the Cerro del Pueblo Formation at the type locality of Cerro del Pueblo, on the edge of Saltillo, Coahuila

The Cerro del Pueblo Formation includes marine, brackish, and non-marine environments, and was laid down in a coastal lowland environment, with Coahuila being on the edge of the Western Interior Seaway at the time. Fossils are abundant in the Cerro del Pueblo Formation, and include dinosaurs and other vertebrates, plants and seeds, and invertebrates including oysters, snails, and other molluscs. The formation is underlain by the Parras Shale and is overlain by the Cerro Huerta Formation.

Paleobiota

Dinosaurs

Ornithischians

Remains of the following ornithischians have been found in the formation:^[3]

Ankylosaurs

Ankylosaurs of the Cerro del Pueblo Formation
Genus	Species	Material	Notes	Images
Ankylosauria[3]	Indeterminate[3]	A femur fragment, phalanx and a possible osteoderm.[3]	Indeterminate ankylosaur remains.[3]
Ankylosauridae[3]	Indeterminate[3]	Osteoderms.[3]	Indeterminate ankylosaurid remains.[3]
Nodosauridae[3]	Indeterminate[3]	A caudal vertebra, osteoderms and a tooth.[3]	Indeterminate nodosaurid remains.[3]

Ceratopsians

Ceratopsians of the Cerro del Pueblo Formation
Genus	Species	Material	Notes	Images
Centrosaurinae[3]	Indeterminate[3]	A partial right squamosal.[3]	Probably represents a new taxon.[3]
Ceratopsidae[3]	Indeterminate[3]	Squamosal fragment, metatarsal, metacarpal, sacral vertebrae, proximal end of femora, proximal end of ulna, possible frill fragments and teeth.[3]	Indeterminate ceratopsid remains.[3]
Chasmosaurinae[3]	Indeterminate[3]	Supraorbital horncores, an orbit, dorsal vertebra, indeterminate cranial fragments, limb bones, and unspecified postcranial elements pertaining to juvenile specimens.[3]	Indeterminate chasmosaurine remains belonging to juvenile specimens.[3]

Ornithopods

Ornithopods of the Cerro del Pueblo Formation
Genus	Species	Material	Notes	Images
Coahuilasaurus[4]	C. lipani[3]		A kritosaurin hadrosaurid	Coahuilasaurus Latirhinus Tlatolophus Velafrons
Hadrosauridae[3]	Indeterminate[3]	A braincase, postorbital, quadrate, laterosphenoid, dentaries, mandibles, maxillae, cervical vertebrae, dorsal vertebrae, sacral vertebrae, caudal vertebrae, neural spines, ribs, ilium, femora, fibulae, tibiae, humeri, ulnae, metatarsals, metacarpals, pedal phalanxes, pedal phalanges, pedal ungula, phalanges, phalanxes, various bone fragments, fibulae, scapulae, radii, coracoids, astragali, indeterminate pelvic bones, ossified tendons, isolated teeth and integumentary impressions.[3]	Indeterminate hadrosaurid remains from numerous specimens.[3]
Kritosaurus[5]	K. navajovius[5]	Predentary, symphyseal processes, rostral portion of dental battery of dentaries, rostral region of premaxillae, and fragments of maxilla.[5]	A kritosaurin hadrosaurid, originally referred to K. navajovius,[5] but reclassified to Coahuilasaurus.
Lambeosaurinae[3]	Indeterminate[3]	Maxillae, premaxillae, quadrate, partial braincase, dentaries, cervical vertebrae, dorsal vertebrae, sacral vertebrae, caudal vertebrae, neural spines, ribs, ilia, ischium, femora, fibulae, tibiae, humeri, ulnae, metatarsals, metacarpals, pedal phalanges, phalanges, pedal unguals, astragali, radii, scapulae, pubes and other unprepared elements.[3]	Indeterminate lambeosaurine remains from numerous specimens, including a large hadrosaurid.[3]
Latirhinus[6]	L. uitstlani[6]	Caudal vertebrae, scapulae, humeri, ulnae, coracoid, metacarpals, manual ungual, ilia, ischia, femora, tibiae, fibula, and astragalus.[6]	Holotype specimen is chimeric as it consists of multiple individuals. Some material from the holotype specimen is assigned to Lambeosaurinae indet. and Saurolophinae indet..[7]
Saurolophinae[3]	Indeterminate[3]	A braincase, brain endocast, dentaries, maxillae, cervical vertebrae, dorsal vertebrae, sacral vertebrae, caudal vertebrae, chevrons, neural spines, ribs, ilium fragments, femora, fibulae, tibiae, humeri, ulnae, metatarsals, phalanges, phalanxes, scapulae, a possible coracoid, radii, ossified tendons, and undescribed juvenile specimens.[3]	Indeterminate saurolophine remains from numerous specimens, including juvenile individuals.[3]
Tlatolophus[8]	T. galorum[8]	An almost complete skull, mandible, partial ilium, partial ischium, a femur, scapula, coracoid, sacral vertebrae, caudal vertebrae, and chevrons.[8]	A parasaurolophin hadrosaur, closely related to Charonosaurus and Blasisaurus.[8]
Velafrons[9]	V. coahuilensis[9]	Dentaries, predentaries, ceratobranchial, premaxillae, maxillae, jugal, quadrate, nasal, skull roof, cervical vertebrae, dorsal vertebrae, sacral vertebrae, caudal vertebrae, neural arches, cervical ribs, ribs, chevrons, scapula, coracoids, humeri, ulnae, radii, metacarpals, manual phalanges, ilium, ischia, pubes, femora, tibiae, astragalus, metatarsals and pedal phalanges.[9]	A lambeosaurine hadrosaurid known only from a juvenile specimen.[9]

Thescelosaurids

Thescelosaurids of the Cerro del Pueblo Formation
Genus	Species	Material	Notes	Images
Thescelosauridae[10]	Indeterminate[10]	A right premaxillary tooth and a posterior sacral vertebral centrum.[10]	Indeterminate thescelosaurid remains.[10]

Theropods

Remains of the following theropods have been found in the formation:^[3]

Theropods of the Cerro del Pueblo Formation
Genus	Species	Material	Notes	Images
Caenagnathidae		3 tibia fragments, distal, proximal and medial shaft elements respectively.[11]	An oviraptorosaur. Two different morphotypes are suggested, a small one, less than a meter in length. And a big morphotype, almost reaching two meters.
Dromaeosaurinae[3]	Indeterminate[3]	A pedal ungual and dentary teeth.[3]	Indeterminate dromaeosaurine remains.[3]
Labocania[12]	L. aguillonae[3]		A teratophonein tyrannosaurine
Mexidracon[13]	M. longimanus[3]	A partial skeleton	A ornithomimid theropod
Paraxenisaurus[14]	P. normalensis[14]	Caudal vertebrae, femur, peses, manual phalanxes, manual ungual, tarsals, metatarsals, metacarpals, pedal phalanx, pedal phalanges, and pedal unguals.[14]	Represents the first known deinocheirid from North America.[14]
cf. Richardoestesia[3]	Indeterminate[3]	A tooth.[3]	A taxon only known from teeth.[3]
"Saltillomimus"	"S. rapidus"	Partial skeleton.[15]	An informally named ornithomimosaur.[15]
Saurornitholestinae[3]	Indeterminate[3]	A pedal ungual, manual unguals and teeth.[3]	Indeterminate saurornitholestine remains.[3]
Theropoda[3]	Indeterminate[3]	A neural arch, complete and fragmented pedal and manual phalanxes, manual unguals, unspecified vertebra, complete and fragmented caudal vertebrae, chevron, proximal end of femur, and unidentified bone fragments.[3]	Indeterminate theropod remains.[3]
Troodontidae[3]	Indeterminate[3]	A pedal phalanx and a tooth.[3]	Indeterminate troodontid remains.[3]
Tyrannosauridae[3]	Indeterminate[3]	A caudal vertebra, indeterminate vertebrae, tibia, fibula, fragments of ungual phalanges, phalanges, and teeth.[3]	Indeterminate tyrannosaurid remains.[3]

Pterosaurs

Pterosaurs of the Cerro del Pueblo Formation
Taxa	Presence	Description	Images
Ichnogenus: Pteraichnus[16]	Saltillo, Coahuila[16]	Specimens kept at the Dinosaur Tracks Museum, of the University of Colorado at Denver and the Secretaría de Educación Pública de Coahuila, Mexico;[16] might also represent Haenamichnus.[17]

Turtles

Turtles of the Cerro del Pueblo Formation
Genus	Species	Material	Notes	Images
Mexichelys[18]	M. coahuilaensis		New genus for Euclastes coahuilaensis, sea turtle
Chedighaii[19]	C. hutchisoni		A bothremydid turtle
Yelmochelys[20]	Y. rosarioae		A stem-kinosternid turtle

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.

Fish

Fish of the Cerro del Pueblo Formation
Genus	Species	Material	Notes	Images
Lepisosteus	L. sp.
Amiidae	Indet.

Fossil eggs

• Porituberoolithus sp.
• Spheroolithus sp.
• ?Prismatoolithus sp.

Mammals

Mammals of the Cerro del Pueblo Formation
Genus	Species	Material	Notes	Images
Cimolomyidae indet.			A cimolomyid multituberculate.[15]
Pediomys	P. cf. elegans		A pediomyid tribosphenidan.[15]
Taeniolabidoidae indet.			A taeniolabidoid multituberculate.[15]
Turgidodon	T. cf. russelli		An alphadontid marsupialiform.[15]

See also

• List of dinosaur-bearing rock formations
• List of fossiliferous stratigraphic units in Mexico