- Lance Formation
The Lance (Creek) Formation is a division of
Late Cretaceous 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 (Lancian land 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.Description
The Lance Formation occurs in the uppermost local rock unit of the
Cretaceous , which was deposited in theMaastrichtian (some 70.6 to 65.5 million years ago).Verify source|date=November 2007 The formation varies in thickness from about 90m (300 feet) inNorth Dakota , to almost 600m (2,000 feet) in parts of Wyoming.At least tens of thousands of Late Cretaceous vertebrate remains have been recovered from the Lance Formation. Fossils ranging from microscopic elements to extensive
bonebed s, with nearly complete, sometimes articulated dinosaur skeletons, have been found.Paleontology
The Lance Formation was laid down by streams, on a coastal plain along the edge of the
Western Interior Seaway . Theclimate was subtropical; there was no cold season nd probably ampleprecipitation Most of the 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. Thebird fauna is mainly comprised of orders still existing today.Birds and Theropods
Theropoda
* "Chirostenotes pergracilis" (Caenagnathidae )Verify source|date=November 2007
* "Ceramornis " (Aves :Charadriiformes ?)Only known from this formation to date]
* "Cimolopteryx " (Aves: Charadriiformes)
* "Dromaeosaurus " (Dromaeosauridae )
* "Graculavus " (Aves)
* "Lonchodytes " (Aves:Neoaves )
* "Palintropus " (Aves:Galliformes ?)
* "Potamornis " (Aves)
* "Ornithomimus velox " (Ornithomimidae )
* "Ricardoestesia " (Dromaeosauridae)
* "Troodon " (Troodontidae )
* "Tyrannosaurus " (Tyrannosauridae )Described from Lance Formation specimen]
*UCMP 143274 (Caenagnathidae?) [Initially believed to be aparrot mandible . This is most unlikely however, as all early parrots seem to have had straight beaks.]Ornithischia
Other vertebrates
Other land
vertebrate s includepterosaur s (e.g. cf. "Azhdarcho "),crocodile s, champsosaurs,lizard s,snake s,turtle s,frog s andsalamander s.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
External links
* [http://www2.nature.nps.gov/geology/paleontology/pub/fossil_conference_6/breithaupt_2.htm Passport-In-Time Microvertebrate Fossil Project]
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