| Lance Formation | |
|---|---|
| Stratigraphic range:Maastrichtian ~70–66 Ma | |
 Badlands in the Lance Formation alongCow Creek near the type locality,Niobrara County, Wyoming | |
| Type | Sedimentary |
| Underlies | Fort Union Formation |
| Overlies | Meeteetse Formation |
| Thickness | up to 600 metres (1,970 ft) |
| Lithology | |
| Primary | Sandstone,siltstone,shale |
| Location | |
| Region | Wyoming |
| Country | United States |
| Type section | |
| Named for | Lance Creek, Wyoming |
TheLance (Creek) Formation is a division ofLate Cretaceous (dating to about 69–66 Ma) rocks in the western United States. Named afterLance Creek, Wyoming, themicrovertebrate fossils and dinosaurs represent important components of the latestMesozoic vertebrate faunas. The Lance Formation is Late Maastrichtian in age (Lancianland mammal age), and shares muchfauna with theHell Creek Formation of Montana and North Dakota, theFrenchman Formation of southwest Saskatchewan, and the lower part of theScollard Formation of Alberta.
The Lance Formation occurs above theBaculites 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.[1]
The formation is described by W.G. Pierce as thick-bedded, buff-colored sandstone, and drab to green shale. It is UpperCretaceous in age.[2]
The formation varies in thickness from about 90 m (300 ft.) inNorth Dakota, to almost 600 m (2,000 ft.) in parts of Wyoming.
The Lance Formation was laid down by streams, on a coastal plain along the edge of theWestern Interior Seaway. Theclimate was subtropical; there was no cold season and probably ampleprecipitation.
At least tens of thousands of Late Cretaceous vertebrate remains have been recovered from the Lance Formation. Fossils ranging from microscopic elements to extensivebonebeds, with nearly complete, sometimesarticulated dinosaur skeletons, have been found.[3] 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 oforders still existing today.
Color key
| Notes Uncertain or tentative taxa are insmall text; |
| Birds reported from the Lance Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic Position | Material | Notes | Images |
A. retusus | Reclassified asPalintropus retusus | |||||
C. major | A possiblecharadriiform bird | |||||
C. petra | Reclassified asLamarqueavis minima[5] | |||||
C. rara |
| A charadriiform | ||||
C. retusa | Reclassified asPalintropus retusus | |||||
C. minima | Reclassified asLamarqueavis minima[5] | |||||
"Cimolopteryx" | "C."maxima |
| Acharadriiform bird, not necessarily closely related toCimolopteryx.[4] | |||
G. augustus |
| A possible charadriiform[6] | ||||
L. minima |
| A charadriiform[5] | ||||
L. petra |
| A charadriiform[5] | ||||
L. estesi |
| A possibleprocellariiform[6] | ||||
"Lonchodytes" | "L."pterygius |
| A possible charadriiform[6] | |||
"P."vetus | A bird similar togruids,idiornithids andpresbyornithids.[6] | |||||
P. retusus |
| A basalornithuromorph belonging toAmbiortiformes.[7] | ||||
P. skutchi | Ahesperornithiform possibly also present in theHell Creek Formation.[8] | |||||
T. clemensi |
| A possible pelecaniform[6] | ||||
Unnamedpresbyornithid | Indeterminate | |||||
Unnamed enantiornithean | Unnamed |
| Anenantiornithean, previously referred to "Ornithomimus"minutus[11] | |||
Unnamedavian | Indeterminate |
| ||||
Unnamed phalacrocoracid | Indeterminate |
| A possiblephalacrocoracid[6] | |||
Unnamed galloanserine | Indeterminate | A possiblegalloanserine[12][13] | ||||
"Unnamed ornithurine A"[4] | Indeterminate | Originally thought to belong toCimolopteryx rara, but probably a new species. Also present in theFrenchman Formation.[4] | ||||
"Unnamed ornithurine C"[4] | Indeterminate |
| Also present in theHell Creek Formation.[4] | |||
"Unnamed ornithurine E"[4] | Indeterminate | Also present in theHell Creek Formation.[4] | ||||
"Unnamed ornithurine F"[4] | Indeterminate | Originally thought to belong to "Cimolopteryx"maxima, but probably a new species.[4] | ||||
An isolated tooth crown of an indeterminate coelurosaur is recovered from the formation.[13]
| Miscellaneouscoelurosaurs of the Lance Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic Position | Material | Notes | Images |
A. amplus | Teeth,type specimen | Dubious tyrannosaurids probably synonymous withTyrannosaurus rex |   .png) | |||
A. cristatus | Teeth,type specimen | |||||
"O." sedens | "Sacrum and fragmentary illium"[14]type specimen | An ornithomimid. | ||||
P. caperatus | Teeth,type specimen | A troodontid | ||||
P. bakkeri | Teeth,type specimen | |||||
T. rex | Several partial specimens and teeth | A tyrannosaurid originally identified from theHell Creek Formation. Also found in theDenver,Ferris,Frenchman,Javelina,Livingston,McRae,North Horn,Scollard, andWillow Creek Formations. Synonyms with type specimens from this formation includeDynamosaurus imperiosus andManospondylus gigas.[15] | ||||
| Trierarchuncus[13] | cf.T. prairiensis |
| Analvarezsaurid originally identified from theHell Creek Formation. | |||
| Caenagnathidae[16][17] | Indeterminate | UCMP 143274 | Previously identified as aparrot[18] | |||
| Troodontinae[13] | Indeterminate | YPM VP 004691 | Not referrable toParonychodon orPectinodon. | |||
| cf.Microraptoria[13] | Indeterminate |
| Potentially the youngest microraptorian specimens, but YPM VP 865 may belong to theUnenlagiinae orHalszkaraptorinae.[13] | |||
| Eudromaeosauria[13] | Indeterminate | YPM VPPU 20589 | ||||
| Ankylosaurs of the Lance Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic Position | Material | Notes | Images |
A. magniventris[19] |
| More than 70 osteoderms and a tooth | Anankylosaurid, originally identified from theHell Creek Formation. |    | ||
| Denversaurus | D. schlessmani | Wyoming | FPDM-V9673,[20][21] formerlyBHI 127327[22] | Anodosaurid, originally identified from theHell Creek Formation.[23] | ||
E. sp.[24] |
| Teeth | Anodosaurid. Fossils have been unearthed in theHell Creek Formation, theFerris Formation, theDinosaur Park Formation, theHorseshoe Canyon Formation, and theDenver Formation.[25][26][27][28][29] | |||
"P. latus"[24] |
| Teeth | Probably anodosaurid, but the teeth could also belong to thePachycephalosauridae.[30] | |||
| Marginocephalians reported from the Lance Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic Position | Material | Notes | Images |
A. sylvestris | "Partial sacrum and pelvis,"[31]type specimen. | Adubious ceratopsid probably synonymous withTriceratops horridus |       | |||
L. gracilis[32] | A ceratopsian | |||||
N. hatcheri | "[One] skull,"[31]type specimen. | A ceratopsid possibly synonymous withTriceratops horridus.[33] Synonyms includeDiceratops hatcheri andDiceratus hatcheri. | ||||
P. wyomingensis | Fragmentary specimens including thetype specimen. | Apachycephalosaur. Synonyms with type specimens from this formation includeTroodon wyomingensis. | ||||
"Palaeoscincus" | "P."latus | "Tooth."[30] | A dubious pachycephalosaur, previously classified as the ankylosaurPalaeoscincus | |||
S. spinifer | A pachycephalosaur possibly synonymous withPachycephalosaurus wyomingensis[34] | |||||
T. latus | Several specimens including thetype specimen. | Aceratopsid possibly synonymous withTriceratops horridus.[33]Torosaurus gladius, with type specimen from this formation, is a synonym. Also present in theFrenchman andHell Creek Formations. | ||||
T. horridus | "Partial skull and skeleton,"[31]type specimen | A ceratopsid, also found in theEvanston,Frenchman,Hell Creek,Laramie, andScollard Formations. Synonyms with type specimens from this formation includeT. ingens andT. sulcatus.[31] | ||||
Indeterminatelambeosaurinae fossils have been found in the Lance Formation.[35]
| Ornithopods of the Lance Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic Position | Abundance | Notes | Images |
E. annectens | Skull, skeletons, including thetype specimen, "mummy", and a bone bed.[36] | A hadrosaurid. Synonyms from this formation includeAnatosaurus annectens andClaosaurus annectens. Also found in theFrenchman,Hell Creek,Laramie andScollard Formations. |   | |||
T. neglectus | Well-preserved skeleton,type specimen | Athescelosaurid.[37] Also found in theFrenchman,Hell Creek,Laramie andScollard Formations. | ||||
T. occidentalis | Teeth, vertebrae, toe bone (includingtype specimen) | Adubious hadrosaurid possibly synonymous withE. annectens | ||||
"T."longiceps | One partial jaw (YPM 616),type specimen | Adubious hadrosaurid possibly synonymous withE. annectens | ||||
Other landvertebrates includepterosaurs (e.g. cf.Quetzalcoatlus),[38] crocodiles,champsosaurs, lizards, snakes, turtles, frogs andsalamanders.
Remains offishes andmammals (i.e.Nanocuris) have also been found in the Lance Formation.
