# Cooper Canyon Formation

The Cooper Canyon Formation is a geological formation of Norian age in Texas. It is one of several formations encompassed by the Dockum Group.
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

| 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. |

### Temnospondyls

Temnospondyls of the Cooper Canyon Formation :
| Genus/Taxon | Species | Unit | Location | Material | Notes | Images |
| Apachesaurus | A. gregorii | Lower (upper) | Post Quarry (MOTT 3624) | Partial skull, mandible and pectoral girdle | The lowest known stratigraphic occurrence of diagnostic Apachesaurus cranial material. |
| Buettnererpeton | B. bakeri | Lower (lower) | Boren Quarry (MOTT 3869) | Two skulls | A metoposaurid temnospondyl. Species was originally assigned to Anaschisma or Metoposaurus before being given its own genus in 2022. | Buettnererpeton bakeri |
| Rileymillerus | R. cosgriffi | Lower (upper) | Post Quarry (MOTT 3624) | Skull and jaws, vertebral intercentra | An unusual small temnospondyl, known only by one specimen. | Buettnererpeton bakeri |

### Archosaurs
#### Phytosaurs

Phytosaurs of the Cooper Canyon Formation :
| Genus/Taxon | Species | Unit | Location | Material | Notes |
| Leptosuchus | L. sp. | Lower (upper) | Post Quarry (MOTT 3624) | Partial skull and mandibles | May represent a distinct species of Leptosuchus from L. crosbiensis and L. studeri. |
| Machaeroprosopus | M. lottorum | Upper | Patricia Site (MOTT 3870) | Two skulls | A derived mystriosuchin phytosaur closely related to and intermediate with Redondasaurus. |
| Machaeroprosopus | M. sp. | Upper | Patricia Site (MOTT 3870) | One skull | A specimen of Machaeoprosopus that appears phylogenetically distinct from M. lottorum. |
| Machaeroprosopus | M. sp. | Middle | Headquarters (MOTT 3892) | Squamosal | The lowest occurrence of Machaeoprosopus in the Dockum Group, defining the base of the Revueltian teilzone in the Cooper Canyon Formation. |
| "Paleorhinus" | "P." cf. sawini | Lower (lower) | Boren Quarry (MOTT 3869) | Skull | A phytosaur similar to "Paleorhinus" sawini, although potentially representing a distinct species. |
| Redondasaurus? | R. gregorii? | Upper | Macy 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 | Images |
| Calyptosuchus | C. wellesi | Lower (lower) | Boren Quarry (MOTT 3869) | | A desmatosuchian aetosaur. Material from Post Quarry named as the new genus and species Scutarx deltatylus in 2016. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Crocodylomorpha indet. | Indeterminate | Lower (upper, lower) | Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869) | Femora | A small crocodylomorph comparable to Hesperosuchus. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Desmatosuchus | D. smalli | Lower (upper) | Post Quarry (MOTT 3624) | Several skulls and partial skeletons, osteoderms | An 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. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Garzapelta | G. muelleri | Middle | UU Sand Creek (MOTT 3882) | Osteoderms and some associated postcrania | Believed to be a paratypothoracin aetosaur, but with lateral osteoderms convergent with desmatosuchins. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Paratypothorax | P. sp. | Lower (upper) | Post Quarry (MOTT 3624) | Osteoderms and some associated postcrania | A paratypothoracin aetosaur. Potentially belongs to a distinct species from P. andressorum, as for other North American Paratypothorax. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Pattisaura | P. gracilis | Middle (upper) | Headquarters South (MOTT 3898) | An articulated skull and postcranial skeleton | An early crocodylomorph. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Poposaurus | P. gracilis | Lower (lower) | Boren Quarry (MOTT 3869) | Femur, cervical vertebra | A bipedal predatory paracrocodylomorph. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Postosuchus | P. kirkpatricki | Upper? Lower (upper) | Patricia Site (MOTT 3870)? Post Quarry (MOTT 3624) | Two skeletons and isolated remains | A 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. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Scutarx | S. deltatylus | Middle Lower (upper) | Headquarters NW (MOTT 3899) Post Quarry (MOTT 3624) | Osteoderms | A desmatosuchine aetosaur based on material formerly assigned to Calyptosuchus wellesi. Known more abundantly in the Chinle Formation. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Shuvosaurus | S. inexpectatus | Upper? Lower (upper, lower) | Patricia Site (MOTT 3870)? Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869) | Skulls and skeleton | Originally 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. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Cf. Stagonolepis? | S.? sp. | Lower (lower) | Boren Quarry (MOTT 3869) | Lateral and caudal paramedian osteoderm | Aetosaur osteoderms compared favourably to Stagonolepis (including Calyptosuchus at the time). | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |
| Typothorax | T. coccinarum | Upper Lower (upper) | Patricia Site (MOTT 3870) Post Quarry (MOTT 3624) | Partial skeleton, braincase, and osteoderms | A typothoracine aetosaur. Also commonly found in the Chinle Formation of Arizona and the Bull Canyon Formation of New Mexico. | Poposaurus gracilis Postosuchus kirkpatricki Scutarx deltatylus Shuvosaurus inexpectatus |

#### 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 |
| Coelophysis | C. bauri | Lower (upper) | Post Quarry (MOTT 3624) | | Material since referred to indeterminate herrerasaurids and neotheropods. |
| Dinosauriformes indet. | Indeterminate | Lower (lower) | Boren Quarry (MOTT 3869) | Two left fibulae | The fibulae are most similar to those of Marasuchus, but notably are three times as long. |
| Dromomeron | D. gregorii | Lower (upper, lower) | Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869) | Four left femora | Lagerpetid pterosauromorphs. |
| Dromomeron | D. romeri | Middle (upper) | Headquarters South (MOTT 3898) | Proximal right tibia | Lagerpetid pterosauromorphs. |
| Herrerasauridae indet. | Indeterminate | Lower (upper) | Post Quarry (MOTT 3624) | Partial hip | Previously referred to Coelophysis bauri by Lehman and Chatterjee (2005). |
| Neotheropoda indet. | Indeterminate | Lower (upper) | Post Quarry (MOTT 3624) | Ilium and tibia | Previously referred to Coelophysis bauri by Lehman and Chatterjee (2005). |
| Soumyasaurus | S. aenigmaticus | Lower (upper) | Post Quarry (MOTT 3624) | Left dentary | A very small silesaurid dinosauriform, type specimen. |
| Technosaurus | T. smalli | Lower (upper) | Post Quarry (MOTT 3624) | Premaxilla and dentary | A 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 | Images |
| cf. Doswellia | cf. D. sp. | Lower (lower) | Boren Quarry (MOTT 3869) | Fragmentary osteoderm | An unusual armoured archosauriform. | Trilophosaurus buettneri Vancleavea campi |
| ?Malerisaurus | ?M. langstoni | Middle 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. | Trilophosaurus buettneri Vancleavea campi |
| Tanystropheidae indet. | Indeterminate | Lower (middle, lower) | Kirkpatrick Quarry (MOTT 3628) Boren Quarry (MOTT 3869) | Two femora | Small tanystropheids comparable to Tanytrachelos and Langobardisaurus. | Trilophosaurus buettneri Vancleavea campi |
| Trilophosaurus | T. buettneri | Lower (lower) | Boren Quarry (MOTT 3869) | Teeth | Herbivorous 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. | Trilophosaurus buettneri Vancleavea campi |
| Trilophosaurus | T. dornorum | Lower (upper, lower) | Post Quarry (MOTT 3624) Lott Hill (MOTT 3878) Boren Quarry (MOTT 3869) | Teeth, jaw elements | Herbivorous 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. | Trilophosaurus buettneri Vancleavea campi |
| Trilophosaurus | T. jacobsi | Lower (lower) | Boren Quarry (MOTT 3869) | Teeth | Herbivorous 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. | Trilophosaurus buettneri Vancleavea campi |
| Vancleavea | V. campi | Lower (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. | Trilophosaurus buettneri Vancleavea campi |

### 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 |
| Argodicynodon | A. boreni | Lower (lower) | Boren Quarry (MOTT 3869) | Skull, mandibles, and postcrania | A placeriine dicynodont, related to the later Placerias. |
| Cf. Clevosaurus | Cf. C. sp. | Lower (upper) | Post Quarry (MOTT 3624) | Premaxilla | A sphenodontian lepidosauromorph, very similar to Clevosaurus. |
| Dicynodontia indet. | Indeterminate | Lower (middle) | MOTT 3610 McCarty Ranch (MOTT 0690) | Cranial fragments, sternum. | Isolated indeterminate dicynodont material. |
| Drepanosauromorpha indet. | Indeterminate | Lower (upper, lower) | Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869) | Two scapulacoracoids (MOTT 3624) | An unusual, possibly arboreal diapsid reptile. |
| Eucynodontia indet. | Indeterminate | Lower | Post Quarry (MOTT 3624) | Jaw bones and teeth | Probable eucynodonts with teeth lacking a cingulum and possessing a large main cusp and 2–3 smaller posterior cusps. |
| Kannemeyeriiformes indet. | Indeterminate | Lower (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. |
| Libognathus | L. sheddi | Upper Middle | Simpson Ranch (MOTT 3874) UU Sand Creek (MOTT 3882) | Skull and dentaries | A procolophonid parareptile, one of the only known from Late Triassic North America. |
| Pachygenelus | P. milleri | Lower (upper) | Post Quarry (MOTT 3624) | Dentary with teeth | Named as a new species of Pachygenelus by Chatterjee (1983), assignment to this genus is doubtful. Material now provisionally regarded as eucynodont. |
| Protoavis | P. texensis | Lower (upper, middle) | Post Quarry (MOTT 3624) Kirkpatrick Quarry (MOTT 3628) | At least two partial skeletons | A problematic taxon purported to be an early avialan, may be a chimaera of different fossils. |
| Sphenodontia indet. | Indeterminate | Lower (upper, lower) | Post Quarry (MOTT 3624) Boren Quarry (MOTT 3869) | Pterygoid and mandible | Sphenodont lepidosauromorphs. |