The Cooper Canyon Formation is a geological formation of Norian age in Texas. It is one of several formations encompassed by the Dockum Group.Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Triassic, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 518–521. .
The type area of the formation is situated in Garza County, Texas, southeast of Lubbock. The Cooper Canyon Formation consist of reddish siltstone and mudstone with lenses of sandstone and conglomerate. Thickness of the formation in the type area is 161.5 meters. It increases to the south, and in some places exceeds 200 m. The formation contains diverse fossils, including vertebrate remains.
Regional equivalents The Bull Canyon Formation in eastern New Mexico is equivalent to the upper part of the Cooper Canyon Formation. Some researchers argue that the latter name should be abandoned. The middle and lower parts of the Cooper Canyon are correlated to the Trujillo and Tecovas formations (respectively) further north in the Texas Panhandle. The lowermost part of the Cooper Canyon Formation may also be correlated to the Colorado City Formation further south at Otis Chalk (Howard County).
Vertebrate fauna
Temnospondyls Temnospondyls of the Cooper Canyon Formation Genus/Taxon Species Unit Location Material Notes ImagesApachesaurusA. gregoriiLower (upper)Post Quarry (MOTT 3624)Partial skull, mandible and pectoral girdleThe lowest known stratigraphic occurrence of diagnostic Apachesaurus cranial material.BuettnererpetonB. bakeriLower (lower)Boren Quarry (MOTT 3869)Two skullsA metoposaurid temnospondyl. Species was originally assigned to Anaschisma or Metoposaurus before being given its own genus in 2022.RileymillerusR. cosgriffiLower (upper)Post Quarry (MOTT 3624)Skull and jaws, vertebral intercentraAn unusual small temnospondyl, known only by one specimen.
Archosaurs Phytosaurs Phytosaurs of the Cooper Canyon Formation Genus/Taxon Species Unit Location Material Notes ImagesLeptosuchusL. sp.Lower (upper)Post Quarry (MOTT 3624)Partial skull and mandiblesMay represent a distinct species of Leptosuchus from L. crosbiensis and L. studeri.MachaeroprosopusM. lottorumUpperPatricia Site (MOTT 3870)Two skullsA derived mystriosuchin phytosaur closely related to and intermediate with Redondasaurus.M. sp.UpperPatricia Site (MOTT 3870)One skullA specimen of Machaeoprosopus that appears phylogenetically distinct from M. lottorum.M. sp.MiddleHeadquarters (MOTT 3892)SquamosalThe lowest occurrence of Machaeoprosopus in the Dockum Group, defining the base of the Revueltian teilzone in the Cooper Canyon Formation."Paleorhinus""P." cf. sawiniLower (lower)Boren Quarry (MOTT 3869)SkullA phytosaur similar to "Paleorhinus" sawini, although potentially representing a distinct species.Redondasaurus?R. gregorii?UpperMacy Ranch (MOTT 3927)Skull and postcranial skeleton (specimen TTUP 9425).Specimens currently only described in unpublished theses, initially referred to a new informal genus "Macysuchus". Referred to R. gregorii by Spielmann and Lucas (2012).
Pseudosuchians Indeterminate paracrocodylomorph and stagonolepidid material is known from the Boren Quarry (MOTT 3869). Pseudosuchians of the Cooper Canyon Formation Genus/Taxon Species Unit Location Material Notes ImagesCalyptosuchusC. wellesiLower (lower)Boren Quarry (MOTT 3869)A desmatosuchian aetosaur. Material from Post Quarry named as the new genus and species Scutarx deltatylus in 2016.Crocodylomorpha indet.IndeterminateLower (upper, lower)Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869)FemoraA small crocodylomorph comparable to Hesperosuchus.DesmatosuchusD. smalliLower (upper)Post Quarry (MOTT 3624)Several skulls and partial skeletons, osteodermsAn armoured aetosaur with large shoulder spines. Type locality of D. smalli, species also known from the Chinle Formation. Some skeletal postcranial material may belong to Paratypothorax.GarzapeltaG. muelleriMiddleUU Sand Creek (MOTT 3882)Osteoderms and some associated postcraniaBelieved to be a paratypothoracin aetosaur, but with lateral osteoderms convergent with desmatosuchins.ParatypothoraxP. sp.Lower (upper)Post Quarry (MOTT 3624)Osteoderms and some associated postcraniaA paratypothoracin aetosaur. Potentially belongs to a distinct species from P. andressorum, as for other North American Paratypothorax.PattisauraP. gracilisMiddle (upper)Headquarters South (MOTT 3898)An articulated skull and postcranial skeletonAn early crocodylomorph.PoposaurusP. gracilisLower (lower)Boren Quarry (MOTT 3869)Femur, cervical vertebraA bipedal predatory paracrocodylomorph.PostosuchusP. kirkpatrickiUpper? Lower (upper)Patricia Site (MOTT 3870)? Post Quarry (MOTT 3624)Two skeletons and isolated remainsA large predatory rauisuchid, type specimen from the Post Quarry. Most rauisuchid material from elsewhere in the southwestern US has also been assigned to Postosuchus kirkpatricki but it is unclear how much of it definitively belongs to Postosuchus. A fifth metatarsal from the Boren Quarry (MOTT 3869) may belong to Postosuchus.ScutarxS. deltatylusMiddle Lower (upper)Headquarters NW (MOTT 3899) Post Quarry (MOTT 3624)OsteodermsA desmatosuchine aetosaur based on material formerly assigned to Calyptosuchus wellesi. Known more abundantly in the Chinle Formation.ShuvosaurusS. inexpectatusUpper? Lower (upper, lower)Patricia Site (MOTT 3870)? Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869)Skulls and skeletonOriginally named as an ornithomimid dinosaur based on its skull, later recognised to be synonymous with poposauroid postcrania named "Chatterjeea elegans". Type specimen is from the Post Quarry, Shuvosaurus has also reported from the Chinle Formation.Cf. Stagonolepis?S.? sp.Lower (lower)Boren Quarry (MOTT 3869)Lateral and caudal paramedian osteodermAetosaur osteoderms compared favourably to Stagonolepis (including Calyptosuchus at the time).TypothoraxT. coccinarumUpper Lower (upper)Patricia Site (MOTT 3870) Post Quarry (MOTT 3624)Partial skeleton, braincase, and osteodermsA typothoracine aetosaur. Also commonly found in the Chinle Formation of Arizona and the Bull Canyon Formation of New Mexico.
Ornithodirans Numerous bones from ornithodirans have been discovered throughout the Cooper Canyon Formation but cannot be assigned to specific genera or clades. However, they are at least variably identifiable as lagerpetids, dinosauromorphs, dinosaurs, saurischians and theropods. Ornithodirans of the Cooper Canyon Formation Genus/Taxon Species Unit Location Material Notes ImagesLower (upper)Post Quarry (MOTT 3624)Material since referred to indeterminate herrerasaurids and neotheropods.Dinosauriformes indet.IndeterminateLower (lower)Boren Quarry (MOTT 3869)Two left fibulaeThe fibulae are most similar to those of Marasuchus, but notably are three times as long.DromomeronD. gregoriiLower (upper, lower)Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869)Four left femoraLagerpetid pterosauromorphs.D. romeriMiddle (upper)Headquarters South (MOTT 3898)Proximal right tibiaHerrerasauridae indet.IndeterminateLower (upper)Post Quarry (MOTT 3624)Partial hipPreviously referred to Coelophysis bauri by Lehman and Chatterjee (2005).Neotheropoda indet.IndeterminateLower (upper)Post Quarry (MOTT 3624)Ilium and tibiaPreviously referred to Coelophysis bauri by Lehman and Chatterjee (2005).SoumyasaurusS. aenigmaticusLower (upper)Post Quarry (MOTT 3624)Left dentaryA very small silesaurid dinosauriform, type specimen.TechnosaurusT. smalliLower (upper)Post Quarry (MOTT 3624)Premaxilla and dentaryA silesaurid dinosauriform, type and only specimen.
Archosauromorphs Fragmentary fossils are identifiable as archosauromorphs, namely members of the Allokotosauria+Prolacerta+Archosauriformes clade. Non-crurotarsan archosauromorphs of the Cooper Canyon Formation Genus/Taxon Species Unit Location Material Notes Imagescf. Doswelliacf. D. sp.Lower (lower)Boren Quarry (MOTT 3869)Fragmentary osteodermAn unusual armoured archosauriform.?Malerisaurus?M. langstoniMiddle Lower (upper, lower)Headquarters North (MOTT 3900) Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869)Dentaries, cervical vertebrae, femur, humerus.A Malerisaurus-like taxon, a small carnivorous azendohsaurid allokotosaur. Three dentaries from the Boren Quarry were misinterpreted as the oldest saurischian dinosaurs in North America, but show affinity to malerisaurines.Tanystropheidae indet.IndeterminateLower (middle, lower)Kirkpatrick Quarry (MOTT 3628) Boren Quarry (MOTT 3869)Two femoraSmall tanystropheids comparable to Tanytrachelos and Langobardisaurus.TrilophosaurusT. buettneriLower (lower)Boren Quarry (MOTT 3869)TeethHerbivorous trilophosaurid allokotosaurs. Of the three species represented in the Boren Quarry, T. dornorum and T. jacobsi are the more common, with T. buettneri represented by only two specimens. T. jacobsi is also common at the Kahle Quarry (NMMNH L-3775) should it belong to the middle Cooper Canyon Formation.T. dornorumLower (upper, lower)Post Quarry (MOTT 3624) Lott Hill (MOTT 3878) Boren Quarry (MOTT 3869)Teeth, jaw elementsT. jacobsiLower (lower)Boren Quarry (MOTT 3869)TeethVancleaveaV. campiLower (upper, lower)Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869)Postcervical vertebrae, osteoderms (MOTT 3624)An unusual armoured semi-aquatic archosauriform. Additional limb bones from the Post and Kirkpatrick quarries may belong to Vancleavea or a related taxon.
Other amniotes Numerous fragmentary limb bones of various reptiles have been collected that cannot be reliably diagnosed to specific clades, though some show similarities to drepanosauromorphs. Indeterminate procolophonid material is known from the Boren Quarry (MOTT 3869). Miscellaneous amniotes of the Cooper Canyon Formation Genus/Taxon Species Unit Location Material Notes ImageArgodicynodonA. boreniLower (lower)Boren Quarry (MOTT 3869)Skull, mandibles, and postcraniaA placeriine dicynodont, related to the later Placerias.Cf. ClevosaurusCf. C. sp.Lower (upper)Post Quarry (MOTT 3624)PremaxillaA sphenodontian lepidosauromorph, very similar to Clevosaurus.Dicynodontia indet.IndeterminateLower (middle)MOTT 3610 McCarty Ranch (MOTT 0690)Cranial fragments, sternum.Isolated indeterminate dicynodont material.Drepanosauromorpha indet.IndeterminateLower (upper, lower)Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869)Two scapulacoracoids (MOTT 3624)An unusual, possibly arboreal diapsid reptile.Eucynodontia indet.IndeterminateLowerPost Quarry (MOTT 3624)Jaw bones and teethProbable eucynodonts with teeth lacking a cingulum and possessing a large main cusp and 2–3 smaller posterior cusps.FabanychusF. monosMiddleHeadquarters Site (MOTT 3898-2)An isolated manual ungualA drepanosauromorph also known from the Chinle Formation; similar to AncistronychusKannemeyeriiformes indet.IndeterminateLower (upper)Post Quarry (MOTT 3624) Meyer's Hill (MOTT 3881)A humerus (MOTT 3881) and a femur (MOTT 3624).Isolated indeterminate kannemeyeriiforms, potentially distinct from Argodicynodon.LibognathusL. sheddiUpper MiddleSimpson Ranch (MOTT 3874) UU Sand Creek (MOTT 3882)Skull and dentariesA procolophonid parareptile, one of the only known from Late Triassic North America.Lower (upper)Post Quarry (MOTT 3624)Dentary with teethNamed as a new species of Pachygenelus by Chatterjee (1983), assignment to this genus is doubtful. Material now provisionally regarded as eucynodont.ProtoavisP. texensisLower (upper, middle)Post Quarry (MOTT 3624) Kirkpatrick Quarry (MOTT 3628)At least two partial skeletonsA problematic taxon purported to be an early avialan, may be a chimaera of different fossils.Sphenodontia indet.IndeterminateLower (upper, lower)Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869)Pterygoid and mandibleSphenodont lepidosauromorphs.
See also List of dinosaur-bearing rock formations
References
Links Bull Canyon Formation of Chinle Group by USGS