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The 'Lance Formation' is a division of Late Cretaceous 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 is coeval 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.

Contents

Occurrence

Importance

Size

Paleontology

See Also

External links

Occurrence

The Lance Formation occurs in the uppermost rock unit of the Cretaceous, which was deposited in the Maastrichtian some 70.6 to 65.5 million years ago.

Importance

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.

Size

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

Paleontology

The Lance Formation was laid down by streams, on a coastal plain along the edge of the Western Interior Seaway. 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.
'Lance Creek dinosaurs' (including birds):

★ Ceratopsians: ''Torosaurus'', ''Triceratops'' (the most abundant dinosaur in this formation)

★ Tyrannosauroids: ''Tyrannosaurus'' (described from the Lance Formation)

★ Hadrosauroids: ''Edmontosaurus''

★ Pachycephalosaurians: ''Pachycephalosaurus''

★ Ankylosaurians: ''Ankylosaurus'', ''Edmontonia''

★ "Hypsilophodontidae": ''Thescelosaurus''

★ Deinonychosaurians: ''Dromaeosaurus'', ''Ricardoestesia'', ''Troodon''

★ Ornithomimosaurians: ''Ornithomimus''

★ Birds: ''Ceramornis'', ''"Cimolopteryx"'', ''Graculavus'', ''Lonchodytes'', '' Palintropus'', ''Potamornis''
Other sauropsids include champsosaurs, turtles, lizards, snakes, crocodiles and pterosaurs.
Remains of fishes, frogs, salamanders and mammals have also been found in the Lance Formation.

See Also

★ List of fossil sites ''(with link directory)''

External links

★ Passport-In-Time Microvertebrate Fossil Project