The Sundance Sea was an

epeiric sea An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large and is either completely surrounded by dry land or connected to an ocean by a river, strait, or "arm of the sea". An inland s ...

that existed in North America during the mid-to-late

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

Period of the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

Era. It was an arm of what is now the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...

, and extended through what is now western

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

into the central western United States. The sea receded when highlands to the west began to rise.

Stratigraphy

The Sundance Sea did not occur at a single time; geological evidence suggests that the Sea was actually a series of five successive marine transgressions—each separated by an

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

hiatus Hiatus may refer to: *Hiatus (anatomy), a natural fissure in a structure * Hiatus (stratigraphy), a discontinuity in the age of strata in stratigraphy *''Hiatus'', a genus of picture-winged flies with sole member species '' Hiatus fulvipes'' * Gl ...

—which advanced and receded from the middle

onward. The terrestrial sediments of the Morrison Formation—eroded from rising highlands to the west—were deposited on top of the marine Sundance sediments as the sea regressed for the last time late in the Jurassic.

Fauna

The Sundance Sea was rich in many types of

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

s. ''

Gryphaea ''Gryphaea'', one of the genera known as devil's toenails, is a genus of extinct oysters, marine bivalve mollusks in the family Gryphaeidae. These fossils range from the Triassic period to the middle Paleogene period, but are mostly restric ...

'' was extremely common, and

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...

teeth have been found. In addition to

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

belemnite Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most ...

s and to an extent ammonites have been found in sediments from the Sundance Sea.

Crinoid Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are ...

s and bivalves would have dotted the seafloor. ''

Ophthalmosaurus ''Ophthalmosaurus'' (meaning "eye lizard" in Greek) is an ichthyosaur of the Jurassic period (165–150 million years ago). Possible remains from the Cretaceous, around 145 million years ago, are also known. It was a relatively medium-sized ich ...

'', a large long ichthyosaur, swam in the seas using its large, long jaws to catch belemnite 'squid'. ''

Pantosaurus ''Pantosaurus'' ("all lizard") is an extinct genus of plesiosaur from the Late Jurassic ( Oxfordian) of what is now Wyoming. It lived in what used to be the Sundance Sea. It was originally named ''Parasaurus'' ("near lizard") by Othniel Charles M ...

'', a 15-20 foot (4.5-6 m) long cryptoclidid plesiosaur, went after the easier-to-catch fish. The largest marine reptile in the Sundance Sea was ''

Megalneusaurus ''Megalneusaurus'' is an extinct genus of large pliosaur that lived in the Sundance Sea during the Kimmeridgian, ~156-152 million years ago, in the Late Jurassic. It was named by paleontologist W. C. Knight in 1895. The genus and type species wa ...

'', a long

pliosaur Pliosauroidea is an extinct clade of plesiosaurs, known from the earliest Jurassic to early Late Cretaceous. They are best known for the subclade Thalassophonea, which contained crocodile-like short-necked forms with large heads and massive toot ...

similar to ''

Liopleurodon ''Liopleurodon'' (; meaning 'smooth-sided teeth') is an extinct genus of large, carnivorous marine reptile belonging to the Thalassophonea, a clade of short-necked pliosaurid plesiosaurs. ''Liopleurodon'' lived from the Callovian Stage of the Mi ...

''.Knight WC. 1895 A new Jurassic plesiosaur from Wyoming. ''Science'' 2: 449. Its fossils have been found in Alaska and Wyoming, which were both covered by the Sundance Sea when it was alive. During the periods of recession,

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s and other

terrestrial animals frequented the shores, as evidenced by the Red Gulch Dinosaur Tracksite near

Shell, Wyoming Shell is a census-designated place (CDP) in Big Horn County, Wyoming, United States. The population was 83 at the 2010 Census. The community is named for the abundance of fossil shells located in the area. Nearby exposed formations such as the ...

References

External links

Map of North America in the middle Jurassic, with the location of the Sundance Sea

Historical oceans Late Jurassic North America Jurassic paleogeography Jurassic Canada Jurassic United States Geology of the Rocky Mountains Jurassic Alberta Jurassic Montana Jurassic geology of Wyoming

Stratigraphy

Fauna

See also

References

External links