# Lance Formation

The Lance (Creek) Formation is a division of Late Cretaceous (dating to about 69–66 Ma) rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas. The Lance Formation is Late Maastrichtian in age (Lancian land mammal age), and shares much fauna with the Hell Creek Formation of Montana and North Dakota, the Frenchman Formation of southwest Saskatchewan, and the lower part of the Scollard Formation of Alberta.
The Lance Formation occurs above the Baculites clinolobatus ammonite marine zone in Wyoming, the top of which has been dated to about 69 million years ago, and extends to the K-Pg boundary, 66 million years ago. However, the characteristic land vertebrate fauna of the Lancian age (which take its name from this formation) is only found in the upper strata of the Lance, roughly corresponding to the thinner equivalent formations such as the Hell Creek Formation, the base of which has been estimated at 66.8 million years old.

## Description

The formation is described by W.G. Pierce as thick-bedded, buff-colored sandstone, and drab to green shale. It is Upper Cretaceous in age.
The formation varies in thickness from about 90 m (300 ft.) in North Dakota, to almost 600 m (2,000 ft.) in parts of Wyoming.

### Depositional environment

The Lance Formation was laid down by streams, on a coastal plain along the edge of the Western Interior Seaway. The climate was subtropical; there was no cold season and probably ample precipitation.

## Paleontology

At least tens of thousands of Late Cretaceous vertebrate remains have been recovered from the Lance Formation. Fossils ranging from microscopic elements to extensive bonebeds, with nearly complete, sometimes articulated dinosaur skeletons, have been found. Most other animals known from the formation are freshwater animals, and some are exclusively freshwater forms (for instance, frogs and salamanders). However, marine fossils are also found in the formation, suggesting that the sea was nearby. The bird fauna is mainly composed of orders still existing today.

### Coelurosaurs

| 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. |

#### Birds

Birds reported from the Lance Formation :
| Genus | Species | Material | Notes |
| Apatornis | A. retusus | | Reclassified as Palintropus retusus |
| Ceramornis | C. major | UCMP 53959 (holotype), a partial coracoid | A possible charadriiform bird |
| Cimolopteryx | C. petra | | Reclassified as Lamarqueavis minima |
| Cimolopteryx | C. rara | YPM 1805 (holotype), a partial coracoid | A charadriiform |
| Cimolopteryx | C. retusa | | Reclassified as Palintropus retusus |
| Cimolopteryx | C. minima | | Reclassified as Lamarqueavis minima |
| "Cimolopteryx" | "C." maxima | UCMP 53973 (holotype), a partial coracoid | A charadriiform bird, not necessarily closely related to Cimolopteryx. |
| Graculavus | G. augustus | AMNH 25223, a partial humerus | A possible charadriiform |
| Lamarqueavis | L. minima | UCMP 53976 (holotype), a partial coracoid | A charadriiform |
| Lamarqueavis | L. petra | AMNH 21911 (holotype), a partial coracoid | A charadriiform |
| Lonchodytes | L. estesi | UCMP 53954 (holotype), a partial tarsometatarsus | A possible procellariiform |
| "Lonchodytes" | "L." pterygius | UCMP 53961 (holotype), a partial carpometacarpus | A possible charadriiform |
| "Palaeotringa" | "P." vetus | ANSP 13361 (holotype), a partial tibiotarsus AMNH 25221, a partial tibiotarsus | A bird similar to gruids, idiornithids and presbyornithids. |
| Palintropus | P. retusus | YPM 513 (holotype), a partial coracoid | A basal ornithuromorph belonging to Ambiortiformes. |
| Potamornis | P. skutchi | UCMP 73103 (holotype), a quadrate tarsometatarsus? | A hesperornithiform possibly also present in the Hell Creek Formation. |
| Torotix | T. clemensi | UCMP 53958, a partial humerus | A possible pelecaniform |
| Unnamed presbyornithid | Indeterminate | AMNH 21929, a partial scapula AMNH 22603, a partial scapula YPM 868, a partial scapula AMNH 22602, a partial sternum | A presbyornithid |
| Unnamed enantiornithean | Unnamed | USNM 2909, a partial metatarsal and pedal phalanges | An enantiornithean, previously referred to "Ornithomimus" minutus |
| Unnamed avian | Indeterminate | UCMP 53960, two partial neck vertebrae | An indeterminate avian |
| Unnamed phalacrocoracid | Indeterminate | AMNH 25272, a femur | A possible phalacrocoracid |
| Unnamed galloanserine | Indeterminate | UCMP 53969, a quadrate YPM VP 59473, a partial skeleton consisting of skull, vertebrae and limb material | A possible galloanserine |
| "Unnamed ornithurine A" | Indeterminate | UCMP 53962, a partial coracoid UCMP 53963, a partial coracoid AMNH uncatalogued, a partial coracoid | Originally thought to belong to Cimolopteryx rara, but probably a new species. Also present in the Frenchman Formation. |
| "Unnamed ornithurine C" | Indeterminate | YPM PU 17020, a partial coracoid | Also present in the Hell Creek Formation. |
| "Unnamed ornithurine E" | Indeterminate | USNM 181923, a partial coracoid USNM 13011, a partial coracoid | Also present in the Hell Creek Formation. |
| "Unnamed ornithurine F" | Indeterminate | UCMP 53957, a partial coracoid ACM 12359, a partial coracoid | Originally thought to belong to "Cimolopteryx" maxima, but probably a new species. |

#### Other coelurosaurs

An isolated tooth crown of an indeterminate coelurosaur is recovered from the formation.
Miscellaneous coelurosaurs of the Lance Formation :
| Genus | Species | Material | Notes | Images |
| Aublysodon | A. amplus | Teeth, type specimen | Dubious tyrannosaurids probably synonymous with Tyrannosaurus rex | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| Aublysodon | A. cristatus | Teeth, type specimen | Dubious tyrannosaurids probably synonymous with Tyrannosaurus rex | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| "Ornithomimus" | "O." sedens | "Sacrum and fragmentary illium" type specimen | An ornithomimid. | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| Paronychodon | P. caperatus | Teeth, type specimen | A troodontid | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| Pectinodon | P. bakkeri | Teeth, type specimen | A troodontid | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| Tyrannosaurus | T. rex | Several partial specimens and teeth | A tyrannosaurid originally identified from the Hell Creek Formation. Also found in the Denver, Ferris, Frenchman, Javelina, Livingston, McRae, North Horn, Scollard, and Willow Creek Formations. Synonyms with type specimens from this formation include Dynamosaurus imperiosus and Manospondylus gigas. | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| Nanotyrannus | N. lancensis | | Synonym of Tyrannosaurus. | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| Trierarchuncus | cf. T. prairiensis | YPM VP 56916, complete manual ungual I YPM VP 57236, complete pedal ungual YPM VP 57402, partial pedal ungual | An alvarezsaurid originally identified from the Hell Creek Formation. | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| Caenagnathidae | Indeterminate | UCMP 143274 | Previously identified as a parrot | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| Troodontinae | Indeterminate | YPM VP 004691 | Not referrable to Paronychodon or Pectinodon. | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| cf. Microraptoria | Indeterminate | YPM VP 865, distal half of metatarsal III YPM VP 57403, ?left pedal ungual II-3 YPM VP 57404, ?left pedal phalanx II-1 YPM VP 57237, distal caudal vertebra | Potentially the youngest microraptorian specimens, but YPM VP 865 may belong to the Unenlagiinae or Halszkaraptorinae. | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |
| Eudromaeosauria | Indeterminate | YPM VPPU 20589 | | Ornithomimus Pectinodon bakkeri toothTyrannosaurus |

### Ornithischia
#### Ankylosaurs

Ankylosaurs of the Lance Formation :
| Genus | Species | Location | Material | Notes | Images |
| Ankylosaurus | A. magniventris | Wyoming | More than 70 osteoderms and a tooth | An ankylosaurid, originally identified from the Hell Creek Formation. | Ankylosaurus Denversaurus Edmontonia |
| Denversaurus | D. schlessmani | Wyoming | FPDM-V9673, formerly BHI 127327 | A nodosaurid, originally identified from the Hell Creek Formation. | Ankylosaurus Denversaurus Edmontonia |
| Edmontonia | E. sp. | Wyoming | Teeth | A nodosaurid. Fossils have been unearthed in the Hell Creek Formation, the Ferris Formation, the Dinosaur Park Formation, the Horseshoe Canyon Formation, and the Denver Formation. | Ankylosaurus Denversaurus Edmontonia |
| "Palaeoscincus" | "P. latus" | Wyoming | Teeth | Probably a nodosaurid, but the teeth could also belong to the Pachycephalosauridae. | Ankylosaurus Denversaurus Edmontonia |

#### Marginocephalians

Marginocephalians reported from the Lance Formation :
| Genus | Species | Material | Notes | Images |
| Agathaumas | A. sylvestris | "Partial sacrum and pelvis," type specimen. | A dubious ceratopsid probably synonymous with Triceratops horridus | Leptoceratops gracilis Nedoceratops hatcheri Pachycephalosaurus wyomingensis Stygimoloch spinifer Torosaurus latus Triceratops horridus |
| Leptoceratops | L. gracilis | | A ceratopsian | Leptoceratops gracilis Nedoceratops hatcheri Pachycephalosaurus wyomingensis Stygimoloch spinifer Torosaurus latus Triceratops horridus |
| Nedoceratops | N. hatcheri | "[One] skull," type specimen. | A ceratopsid possibly synonymous with Triceratops horridus. Synonyms include Diceratops hatcheri and Diceratus hatcheri. | Leptoceratops gracilis Nedoceratops hatcheri Pachycephalosaurus wyomingensis Stygimoloch spinifer Torosaurus latus Triceratops horridus |
| Pachycephalosaurus | P. wyomingensis | Fragmentary specimens including the type specimen. | A pachycephalosaur. Synonyms with type specimens from this formation include Troodon wyomingensis. | Leptoceratops gracilis Nedoceratops hatcheri Pachycephalosaurus wyomingensis Stygimoloch spinifer Torosaurus latus Triceratops horridus |
| "Palaeoscincus" | "P." latus | "Tooth." | A dubious pachycephalosaur, previously classified as the ankylosaur Palaeoscincus | Leptoceratops gracilis Nedoceratops hatcheri Pachycephalosaurus wyomingensis Stygimoloch spinifer Torosaurus latus Triceratops horridus |
| Stygimoloch | S. spinifer | | A pachycephalosaur possibly synonymous with Pachycephalosaurus wyomingensis | Leptoceratops gracilis Nedoceratops hatcheri Pachycephalosaurus wyomingensis Stygimoloch spinifer Torosaurus latus Triceratops horridus |
| Torosaurus | T. latus | Several specimens including the type specimen. | A ceratopsid possibly synonymous with Triceratops horridus. Torosaurus gladius, with type specimen from this formation, is a synonym. Also present in the Frenchman and Hell Creek Formations. | Leptoceratops gracilis Nedoceratops hatcheri Pachycephalosaurus wyomingensis Stygimoloch spinifer Torosaurus latus Triceratops horridus |
| Triceratops | T. horridus | "Partial skull and skeleton," type specimen | A ceratopsid, also found in the Evanston, Frenchman, Hell Creek, Laramie, and Scollard Formations. Synonyms with type specimens from this formation include T. ingens and T. sulcatus. | Leptoceratops gracilis Nedoceratops hatcheri Pachycephalosaurus wyomingensis Stygimoloch spinifer Torosaurus latus Triceratops horridus |

#### Ornithopods

Indeterminate lambeosaurinae fossils have been found in the Lance Formation.
Ornithopods of the Lance Formation :
| Genus | Species | Abundance | Notes | Images |
| Edmontosaurus | E. annectens | Skull, skeletons, including the type specimen, "mummy", and a bone bed. | A hadrosaurid. Synonyms from this formation include Anatosaurus annectens and Claosaurus annectens. Also found in the Frenchman, Hell Creek, Laramie and Scollard Formations. | Edmontosaurus annectens Thescelosaurus neglectus |
| Thescelosaurus | T. neglectus | Well-preserved skeleton, type specimen | A thescelosaurid. Also found in the Frenchman, Hell Creek, Laramie and Scollard Formations. | Edmontosaurus annectens Thescelosaurus neglectus |
| Thespesius | T. occidentalis | Teeth, vertebrae, toe bone (including type specimen) | A dubious hadrosaurid possibly synonymous with E. annectens | Edmontosaurus annectens Thescelosaurus neglectus |
| "Trachodon" | "T." longiceps | One partial jaw (YPM 616), type specimen | A dubious hadrosaurid possibly synonymous with E. annectens | Edmontosaurus annectens Thescelosaurus neglectus |

### Other vertebrates

Other land vertebrates include pterosaurs (e.g. cf. Azhdarcho), crocodiles, champsosaurs, lizards, snakes, turtles, frogs and salamanders.
Remains of fishes and mammals (i.e. Nanocuris) have also been found in the Lance Formation.