Lance Formation

Lance Formation Stratigraphic range: Maastrichtian, 69–66 Ma PreЄ Є O S D C P T J K Pg N ↓
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

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

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.^[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 of orders still existing today.

Coelurosaurs

UCMP 143274 (Caenagnathidae?)^[4][5]

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	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.[6]
	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[6]). 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."[7]	An ornithurine, possibly a hesperornithiform
Presbyornithidae indet.	Indeterminate			Three partial shoulder blades and a partial breastbone	A presbyornithid[8]
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[9]
Unnamed neornithine	Unnamed			Two fragmentary neck vertebrae	A neornithine[8]
Unnamed phalacrocoracid	Unnamed			Femur	A phalacrocoracid[8]

Other Coelurosaurs

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 Tyrannosaurus
	A. cristatus			Teeth, type specimen
"Ornithomimus"	"O." sedens			"Sacrum and fragmentary illium"[10] type specimen	An ornithomimid.
Paronychodon	P. caperatus			Teeth, type specimen	A troodontid
Pectinodon	P. bakkeri			Teeth, type specimen	A troodontid
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.

Ornithischia

Ankylosaurs

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.	Ankylosaurus
Denversaurus	D. schlessmani[11]			Skull (the type specimen)	A nodosaurid

Marginocephalians

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 gracilis Pachycephalosaurus wyomingensis 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, Hell Creek, Laramie, and Scollard Formations. Synonyms with type specimens from this formation include T. ingens and T. sulcatus.[12]

Ornithopods

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.	Edmontosaurus annectens Thescelosaurus neglectus
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

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

• List of fossil sites (with link directory)
• List of dinosaur-bearing rock formations

Footnotes

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. Silver, Mark (August 2, 2014) "The Dinosaur Surveyors" The American Surveyor Frederick Maryland
4. Stidham, 1998
5. Dyke, GJ; Mayr, G. (1999). "Did parrots exist in the Cretaceous period?". Nature 399 (6734): 317–318. doi:10.1038/20583.
6. Federico L. Agnolin (2010). "An avian coracoid from the Upper Cretaceous of Patagonia, Argentina". Stvdia Geologica Salmanticensia 46 (2): 99–119.
7. "Table 11.1," in Weishampel, et al. (2004). Page 215.
8. Hope, 2002
9. 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.
10. "Table 6.1," in Weishampel, et al. (2004). Page 139.
11. 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).
12. "Table 23.1," in Weishampel, et al. (2004). Page 496.
13. 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

• Passport-In-Time Microvertebrate Fossil Project