Lance Formation

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Lance Formation
Stratigraphic range: Maastrichtian, 69–66Ma
Lance Fm.jpg
Badlands in the Lance Formation along Cow 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

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.[1]

Description[edit]

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.[2]

The formation varies in thickness from about 90m (300 feet) in North Dakota, to almost 600m (2,000 feet) in parts of Wyoming.

Depositional Environment[edit]

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[edit]

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[edit]

UCMP 143274 (Caenagnathidae?)[3][4]

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[edit]

Birds reported from the Lance Formation
Genus Species Location Stratigraphic Position Material Notes Images

Apatornis

A. retusus

Partial coracoid

Reclassified as Palintropus retusus

Ceramornis

C. major

Partial coracoid

A possible charadriiform

Cimolopteryx

C. maxima

Partial coracoid

A charadriiform, also present in the Hell Creek Formation

C. petra

Partial coracoid

Possibly referable to the genus Lamarqueavis.[5]

C. rara

Partial coracoid

A charadriiform, also present in the Frenchman Formation.

C. retusa

Partial coracoid

Reclassified as Palintropus retusus

"Cimolopteryx"

"C." minima

Partial coracoid

A charadriiformes previously referred to Cimolopteryx but belonging to a new genus (or possibly Lamarqueavis[5]). Also present in the Hell Creek Formation

Graculavus

G. augustus

Partial humerus

A possible charadriiform

Ichthyornis?

I.? sp.

Partial sacrum

An ichthyornithiform

Lonchodytes

L. estesi

Partial tarsometatarsus

A procellariiform

"Lonchodytes"

"L." pterygius

Partial carpometacarpus

A neoavian, formerly classified as Lonchodytes

"Palaeotringa"

"P." vetus

Two partial tibiotarsi

A bird similar to gruids, idiornithids and presbyornithids. Formerly classified as Palaeotringa

Palintropus

P. retusus

Partial coracoid

A basal ornithuromorph belonging to Ambiortiformes.

Potamornis

P. skutchi

"Quadrate and postcranial elements."[6]

An ornithurine, possibly a hesperornithiform

Presbyornithidae indet.

Indeterminate

Three partial shoulder blades and a partial breastbone

A presbyornithid[7]

Torotix

T. clemensi

Partial humerus

A possible charadriiform or pelecaniform

Unnamed enantiornithine

Unnamed

Partial MTII and pedal phalanges

An enantiornithine, previously referred to "Ornithomimus" minutus[8]

Unnamed neornithine

Unnamed

Two fragmentary neck vertebrae

A neornithine[7]

Unnamed phalacrocoracid

Unnamed

Femur

A phalacrocoracid[7]

Other Coelurosaurs[edit]

Misc Coelurosaurs of the Lance Formation
Genus Species Location Stratigraphic Position Material Notes Images

Aublysodon

A. amplus

Teeth, type specimen

Dubious tyrannosaurids probably synonymous with Tyrannosaurus rex

Pectinodon bakkeri tooth
Cast of a Lance Struthiomimus sedens specimen (BHI 1266)
Tyrannosaurus

A. cristatus

Teeth, type specimen

Ornithomimus

Indeterminate

An indeterminate ornithomimid

Paronychodon

P. caperatus

Teeth, type specimen

A troodontid

Pectinodon

P. bakkeri

Teeth, type specimen

A troodontid, previously classified as Troodon bakkeri or Troodon formosus.

Ricardoestesia

R. cf. gilmorei

Teeth

Dromaeosaurids

R.? isosceles

Indeterminate

Struthiomimus

S. sedens

"Sacrum and fragmentary illium",[9] type specimen

An ornithomimid. Previously classified as Ornithomimus sedans.

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, Kirtland, Livingston, McRae, North Horn, Scollard, Tornillo, and Willow Creek Formations. Synonyms with type specimens from this formation include Dynamosaurus imperiosus and Manospondylus gigas.

Dromaeosauridae

Indeterminate spp.

Teeth

At least one species of indeterminate dromaeosaurid (Currie, Rigby and Sloan, 1990).

Ornithischia[edit]

Ankylosaurs[edit]

Ankylosaurs of the Lance Formation
Genus Species Location Stratigraphic Position Abundance Notes Images

Ankylosaurus

A. magniventris

An ankylosaurid, originally identified from the Hell Creek Formation.

Edmontonia

E. schlessmani[10]

Skull (the type specimen)

A nodosaurid possibly synonymous with Edmontonia rugosidens.[11] Synonymous with Denversaurus schlessmani.

Marginocephalians[edit]

Marginocephalians reported from the Lance Formation
Genus Species Location Stratigraphic Position Material Notes Images

Agathaumas

A. sylvestris

"Partial sacrum and pelvis,"[12] type specimen.

A dubious ceratopsid probably synonymous with Triceratops horridus

Leptoceratops

L. gracilis

A ceratopsian

Nedoceratops

N. hatcheri

"[One] skull,"[12] type specimen.

A ceratopsid possibly synonymous with Triceratops horridus.[13] Synonyms include Diceratops hatcheri and Diceratus hatcheri.

Pachycephalosaurus

P. wyomingensis

Fragmentary specimens including the type specimen.

A pachycephalosaur. Synonyms with type specimens from this formation include Troodon wyomingensis.

"Palaeoscincus"

"P." latus

"Tooth."[14]

A dubious pachycephalosaur, previously classified as the ankylosaur Palaeoscincus

Stygimoloch

S. spinifer

A pachycephalosaur possibly synonymous with Pachycephalosaurus wyomingensis[15]

Torosaurus

T. latus

Several specimens including the type specimen.

A ceratopsid possibly synonymous with Triceratops horridus.[13] Torosaurus gladius, with type specimen from this formation, is a synonym. Also present in the Frenchman and Hell Creek Formations.

Triceratops

T. horridus

"Partial skull and skeleton,"[12] type specimen

A ceratopsid, also found in the Evanston, Frenchman, Kirtland, Hell Creek, Laramie, and Scollard Formations. Synonyms with type specimens from this formation include T. ingens and T. sulcatus.[12]

Ornithopods[edit]

Ornithopods of the Lance Formation
Genus Species Location Stratigraphic Position Abundance Notes Images

Edmontosaurus

E. annectens

Skull, skeletons, including the type specimen and "mummy".

A hadrosaurid. Synonyms from this formation include Anatosaurus annectens and Claosaurus annectens. Also found in the Frenchman, Hell Creek, Laramie and Scollard Formations.

Thescelosaurus

T. neglectus

Well-preserved skeleton, type specimen

A thescelosaurid.[16] Also found in the Frenchman, Hell Creek, Laramie and Scollard Formations.

Thespesius

T. occidentalis

Teeth, vertebrae, toe bone (including type specimen)

A dubious hadrosaurid possibly synonymous with E. annectens

"Trachodon"

"T." longiceps

One partial jaw (YPM 616), type specimen

A dubious hadrosaurid possibly synonymous with E. annectens

Other vertebrates[edit]

Other land vertebrates include pterosaurs (e.g. cf. Azhdarcho), crocodiles, champsosaurs, lizards, snakes, turtles, frogs and salamanders.

Remains of fishes and mammals have also been found in the Lance Formation.

See also[edit]

Footnotes[edit]

  1. ^ Lehman, T. M., Mcdowell, F. W., & Connelly, J. N. (2006). First isotopic (U-Pb) age for the Late Cretaceous Alamosaurus vertebrate fauna of West Texas, and its significance as a link between two faunal provinces. Journal of Vertebrate Paleontology, 26(4), 922-928.
  2. ^ Pierce, W.G., 1997, Geologic map of the Cody 1 degree x 2 degrees quadrangle, northwestern Wyoming: U.S. Geological Survey, Miscellaneous Geologic Investigations Map I-2500, scale 1:250000.
  3. ^ Stidham, 1998
  4. ^ Dyke, GJ; Mayr, G. (1999). "Did parrots exist in the Cretaceous period?". Nature 399 (6734): 317–318. doi:10.1038/20583.
  5. ^ a b Federico L. Agnolin (2010). "An avian coracoid from the Upper Cretaceous of Patagonia, Argentina". Stvdia Geologica Salmanticensia 46 (2): 99–119. 
  6. ^ "Table 11.1," in Weishampel, et al. (2004). Page 215.
  7. ^ a b c Hope, 2002
  8. ^ Chiappe, L. M., and Walker, C. A. (2002) Skeletal morphology and systematics of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes): In: Mesozoic Birds, above the heads of Dinosaurs, University of California Press, 240-267.
  9. ^ "Table 6.1," in Weishampel, et al. (2004). Page 139.
  10. ^ Bakker, R.T. (1988). Review of the Late Cretaceous nodosauroid Dinosauria: Denversaurus schlessmani, a new armor-plated dinosaur from the Latest Cretaceous of South Dakota, the last survivor of the nodosaurians, with comments on Stegosaur-Nodosaur relationships. Hunteria 1(3):1-23.(1988).
  11. ^ Vickaryous, M.K., Maryańska, T., and Weishampel, D.B., (2004). "Ankylosauria". In Weishampel, D. B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria (Second Edition). University of California Press. pp. 363–392. ISBN 0-520-24209-2. 
  12. ^ a b c d "Table 23.1," in Weishampel, et al. (2004). Page 496.
  13. ^ a b Scannella, J. and Horner, J.R. (2010). "Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny." Journal of Vertebrate Paleontology, 30(4): 1157 - 1168. doi:10.1080/02724634.2010.483632
  14. ^ "Table 17.1," in Weishampel, et al. (2004). Page 368.
  15. ^ Horner J.R. and Goodwin, M.B. (2009). "Extreme cranial ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus." PLoS ONE, 4(10): e7626. Online full text
  16. ^ Boyd, Clint A.; Brown, Caleb M.; Scheetz, Rodney D.; Clarke, Julia A. (2009). "Taxonomic revision of the basal neornithischian taxa Thescelosaurus and Bugenasaura". Journal of Vertebrate Paleontology 29 (3): 758–770. doi:10.1671/039.029.0328. 

External links[edit]