The Kirtland Formation (originally the Kirtland Shale) is a sedimentary geological formation.

Description The Kirtland Formation is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation. It is found in the San Juan Basin in the states of New Mexico and Colorado, in the United States of America.

The base of the Kirtland Formation and its lowest sub-unit, the Hunter Wash Member, has been dated to 75.02 ± 0.13 Ma. Together with the upper part of the underlying Fruitland Formation, this contains fossils representing the Hunter Wash local fauna. The border between the Hunter Wash Member and overlying Farmington Member dates to approximately 74 million years ago. The top of the Farmington Member and bottom of the overlying De-na-zin Member has been radiometrically dated to 73.83 ± 0.18 Ma ago. The top of the De-na-zin Member, which contains the Willow Wash local fauna, has been dated to 73.49 ± 0.25 Ma ago.

Overlying the De-na-zin Member is a unit called the Naashoibito Member. This has often been considered to be part of the Kirtland formation, but more recently has been transferred back to the overlying Ojo Alamo Formation, which it had originally been part of.

History of investigation The formation was named by C.M. Bauer in 1916 for exposures near the Kirtland Post Office.

Stratigraphy

Vertebrate paleofauna

Dinosaurs Ornithischians Ankylosaurids Ankylosaurids reported from the Kirtland Formation Genus Species Member Material NotesImagesAhshislepeltaA. minor Hunter WashA partial girdle, scapulocoracoids, humerus, proximal portion of the radius, cervical and/or dorsal vertebrae, complete and fragmentary thoracic osteoderms, and other unidentifiable postcranial fragments.An ankylosaurine ankylosaurid part of the Hunter Wash Member.NodocephalosaurusN. kirtlandensis De-na-zinA partial skull.An ankylosaurine ankylosaurid that has cranial ornamentation similar to Akainacephalus, an ankylosaur from the Kaiparowits Formation.ZiapeltaZ. sanjuanensis Hunter Wash De-na-zin A complete skull, [two] first cervical half-rings, fragmentary second cervical half ring, and numerous fragmentary osteoderms. An ankylosaurine ankylosaurid closely related to Scolosaurus. Ceratopsians Ceratopsians reported from the Kirtland Formation Genus Species Member Material NotesImagesBisticeratops B. froeseorum FarmingtonA nearly complete skull.A chasmosaurine ceratopsid, originally identified as a specimen of Pentaceratops. NavajoceratopsN. sullivani Hunter Wash A parietal, squamosal fragments, fused jugal\epijugal and other unidentified cranial fragments. A chasmosaurine ceratopsid that has been hypothesized to form an anagenetic series with several other chasmosaur species, including Terminocavus.PentaceratopsP. fenestratusA near-complete skull.Holotype considered undiagnostic. May be the same as Navajoceratops or Terminocavus.P. sternbergiA chasmosaurine ceratopsid. Specimens from the Kirtland Formation have been reassigned to Navajoceratops, Terminocavus, and Bisticeratops, with definitive specimens limited to the Fruitland Formation.TerminocavusT. sealeyi Hunter Wash A parietal, partial squamosal, jugal, epijugal, partial quadratojugal, partial sacrum and vertebral fragments. A chasmosaurine ceratopsid that has been hypothesized to form an anagenetic series with several other chasmosaur species, including Navajoceratops.TitanoceratopsT. ouranosA partial skull, syncervical vertebrae, cervical vertebrae, dorsal vertebrae, sacral vertebrae, caudal vertebrae, ribs, humeri, radius, femora, tibiae, fibula, ilia, ischia, and ossified tendons.Possibly represents a junior synonym of Pentaceratops, holotype may possibly have come from the Fruitland Formation.

Pachycephalosaurids Pachycephalosaurids reported from the Kirtland Formation Genus Species Member Material NotesImagesSphaerotholusS. goodwini De-na-zinA partial skull lacking the facial and palatal elements.A pachycephalosaurine pachycephalosaurid. StegocerasS. novomexicanum Hunter WashAn incomplete parietal.A basal pachycephalosaurid also known from the upper Fruitland Formation.

Ornithopods Ornithopods reported from the Kirtland Formation Genus Species Member Material NotesImagesAhshislesaurusA. wimaniHunter WashA partial skull and mandible, three cervical vertebraeA kritosaurin hadrosaurid from the Hunter Wash Member. Several isolated bones and a partial skeleton from the same strata may also belong to this taxon AnasazisaurusA. horneriFarmingtonAn incomplete skull consisting of premaxillae, nasals, maxilla, lacrimal, jugal, prefrontal, postorbital, squamosal, frontal, parietal, and fragment of dentary with teeth.A kritosaurin hadrosaurid from the Farmington Member.KritosaurusK. navajoviusDe-na-zin[Two] incomplete skulls, an atlas, axis and cervical vertebrae.A kritosaurin hadrosaurid also known from the Cerro del Pueblo Formation of Mexico.NaashoibitosaurusN.ostromi De-na-zinA skull lacking the premaxillae and mandible, a partial humerus, cervical vertebrae and dorsal vertebrae.A kritosaurin hadrosaurid, distinct from Kritosaurus.ParasaurolophusP. tubicen De-na-zin[Two] incomplete and fragmentary skulls.A lambeosaurine hadrosaurid known from partial cranial remains.P. cyrtocristatus Hunter WashPartial skull and nearly complete skeleton, partial juvenile skull.May instead be from the upper Fruitland Formation.

Saurischians Sauropods Sauropods of the Kirtland Formation Genus Species Member Material NotesImagesAlamosaurusA. sanjuanensisSpecimens actually from the Naashoibito member of the Ojo Alamo Formation

Theropods Theropods of the Kirtland Formation Genus Species Member Material NotesImagesAublysodonA. mirandus Hunter WashRemains are now referred to Bistahieversor, although these remains may possibly have come from the Fruitland Formation.BistahieversorB. sealeyi Hunter WashAn articulated skull and undescribed postcranial skeleton of an adult individual, and an incomplete skull and postcranial skeleton of a juvenile individual.A eutyrannosaur tyrannosauroid also known from the Fruitland Formation.CaenagnathidaeIndeterminate De-na-zinA nearly complete right tibiaIndeterminate caenagnathid remains.DaspletosaurusIndeterminate Hunter WashRemains are now referred to Bistahieversor, although these remains may possibly have come from the Fruitland Formation.DinevenatorD. robustus De-na-zinA nearly complete frontalOriginally assigned to Saurornitholestes, subsequently recognized as a troodontid, and tentatively assigned to the genus Xenovenator in early 2026. Moved to its own genus later that year.DromaeosauridaeIndeterminateNumerous isolated teeth.Indeterminate dromaeosaurid remains.OrnithomimidaeIndeterminate De-na-zinA distal end of a phalanx, and [two] partial manual unguals.Indeterminate ornithomimid remains.SaurornitholestesS. sullivani De-na-zinA nearly complete frontal.A saurornitholestine dromaeosaurid, sister taxa to Saurornitholestes langstoni.Struthiomimuscf. S. altusA centrum of a dorsal vertebra, distal portion of a metatarsal, and proximal phalanx.Indeterminate remains that may belong to Struthiomimus altus.TyrannosauridaeIndeterminateA partial skeleton, dentary, metatarsal, and numerous teeth.Indeterminate tyrannosaurid material.cf. TyrannosauriniIndeterminate Hunter WashA left tibia.Indeterminate tyrannosaurin material.

Pterosaurs Pterosaurs of the Kirtland Formation Genus Species Location Member Abundance NotesImagesNavajodactylusN. boerei Hunter Wash MemberPartial phalanx and ulna fragmentA possible azhdarchid pterosaur known from fragmentary remains.

Crurotarsans Crurotarsans of the Kirtland Formation Genus Species Location Member Abundance Notes ImagesBrachychampsaB. montana De-na-zinMember of the Willow Wash local fauna.DenazinosuchusD. kirtlandicus De-na-zinMember of the Willow Wash local fauna.LeidyosuchusIndeterminate De-na-zinMember of the Willow Wash local fauna.

Turtles Turtles of the Kirtland Formation Genus Species Location Member Abundance NotesImagesBasilemysB. nobilis De-na-zinMember of the Willow Wash local fauna.DenazinemysD. nodosa De-na-zinMember of the Willow Wash local fauna.NeurankylusN. baueri De-na-zinMember of the Willow Wash local fauna.PlastomenusP. robustus De-na-zinMember of the Willow Wash local fauna.ThescelusT. hemispherica De-na-zinMember of the Willow Wash local fauna.

Bony fish Bony fishes of the Kirtland Formation Genus Species Location Member Abundance NotesMelviusM. chauliodous De-na-zinMember of the Willow Wash local fauna.

Cartilaginous fish Cartilaginous fish of the Kirtland Formation Genus Species Location Member Abundance NotesMyledaphusM. bipartitus De-na-zinMember of the Willow Wash local fauna.

See also List of stratigraphic units with dinosaur body fossils

References

Bibliography