| Prida Formation | |
|---|---|
| Stratigraphic range: Triassic | |
| Type | Formation |
| Location | |
| Region | Nevada |
| Country | United States |
The Prida Formation is a geologic formation in northwestern Nevada. It preserves fossils dating back to the Triassic period.
The Prida Formation, along with the Favret Formation, constitute one of the recognized geological formations within the Star Peak Group of northwestern Nevada. These two formations are linked by a single member, known as the Fossil Hill Member. In the Prida Formation, this member outcrops in the western Humboldt Range, while the Favret Formation, outcrops in the Augusta Mountains, where it reaches up to more than 300 metres (980 ft) thick. Although they overlap substantially, the two formations do not share precisely the same age, the Prida unit dates from the Middle to Late Anisian, while the Favret unit dates only from the Late Anisian, between approximately 244 and 242 million years ago. [1]
The Fossil Hill Member has received extensive interest from paleontological research for its large quantity of marine fossils dating from the Middle Triassic. The environment preserved in the Fossil Hill contains some of the earliest marine reptile communities including Ichthyosaurs and Pistosaurs. Other fossils from this unit include invertebrates such as ceratitid ammonoids and bivalves as well as hybodont sharks and bony fish like Saurichthyes and Birgeria. [2]
In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 247.2 million years ago until 242 million years ago. The Anisian Age succeeds the Olenekian Age and precedes the Ladinian Age.
Cymbospondylus is an extinct genus of large ichthyosaurs, of which it is among the oldest representatives, that lived from the Lower to Middle Triassic in what are now North America and Europe. The first known fossils of this taxon are a set of more or less complete vertebrae which were discovered in the 19th century in various mountain ranges of Nevada, in the United States, before being named and described by Joseph Leidy in 1868. It is in the beginning of the 20th century that more complete fossils were discovered through several expeditions launched by the University of California, and described in more detail by John Campbell Merriam in 1908, thus visualizing the overall anatomy of the animal. While many species have been assigned to the genus, only five are recognized as valid, the others being considered synonymous, doubtful or belonging to other genera. Cymbospondylus was formerly classified as a representative of the Shastasauridae, but more recent studies consider it to be more basal, view as the type genus of the Cymbospondylidae.
Augustasaurus is an extinct genus of sauropterygians that lived during the Anisian stage of the Middle Triassic in what is now North America. Only one species is known, A. hagdorni, described in 1997 from fossils discovered in the Favret Formation, Nevada, USA.
The Favret Formation is a Triassic geologic formation. The Favret outcrops in the Augusta, New Pass and Fish Creek ranges of north central Nevada and consists of limestone, shale and siltstone.
Thalattoarchon is a genus of large, Middle Triassic predatory ichthyosaur from North America, containing the single species T. saurophagis. The taxon was described in 2013 from a single specimen discovered in the Favret Formation in Nevada. The generic name, meaning "ruler of the seas", refers to its status as an apex predator, while the specific epithet, meaning "lizard eater", alludes to its carnivorous diet. The classification of this genus within the ichthyosaurs is much debated, being either classified within the clade Merriamosauria or in the more basal family Cymbospondylidae.
The Virgin Formation is a geologic formation in Utah. It preserves fossils dating back to the Triassic period.
The Thaynes Group, Thaynes Formation in older literature, is a geologic group in eastern Idaho, western Wyoming, Utah and eastern Nevada. It includes the Sinbad Formation, Virgin Formation and Shnabkaib Formation. The Thaynes Group is of marine origin. Its formations are interbedded with layers of the non-marine Moenkopi Group.
The Winnemucca Formation is a Triassic period geologic formation in northwestern Nevada, USA. It is found in the Sonoma Range in Humboldt County.
The Osobb Formation is a geologic formation in Nevada. It preserves fossils dating back to the Triassic period.
The Priada Formation is a geologic formation in Nevada. It preserves fossils dating back to the Triassic period.
The Augusta Mountain Formation is a geologic formation in Nevada. It preserves fossils dating back to the Triassic period.
The Dun Glen Formation is a geologic formation in Nevada. It preserves fossils dating back to the Triassic period.
The Excelsior Formation is a geologic formation in Nevada. It preserves fossils dating back to the Triassic period.
The Grantsville Formation is a geologic formation in Nevada. It preserves fossils dating back to the Triassic period.
The Hoyt Canyon Formation is a geologic formation in Nevada. It preserves fossils dating back to the Triassic period.
The Luning Formation is a geologic formation in Nevada. It preserves fossils dating back to the Triassic period. The lowermost strata dates to the late Carnian-early Norian boundary.
The Vester Formation is a geologic formation in Oregon which preserves fossils dating back to the Triassic period. The partial skeleton of a new genus of basal thalattosaur has been recovered from the Brisbois Member of this formation. The Brisbois Member, which dates to between the Carnian and Norian, is a marine sequence primarily composed of fine-grained clastic sedimentary rocks with fissile mudstones of black, green or gray variety broken up by widely spaced intervals of calcirudite beds and calcareous conglomerate. The formation formed between two parallel island arcs, that of the Baker Terrane and the Olds Ferry Terrane. The formation mostly consists of reworked chert grains from the Baker Terrane. In addition to the remains of the basal thalattosaur, fragmentary and undescribed remains exist of an ichthyosaur, archosaur, and a hybodontid shark as well as many invertebrate fossils.
The Star Peak Group is a geologic group in Nevada. It preserves fossils dating back to the Triassic period. The group is named for Star Peak.
The Wordie Creek Formation is an uppermost Permian and Lower Triassic geologic formation in Greenland, outcrops of which are located in Northeast Greenland National Park. In 2017, it was suggested to be raised to group status, as the Wordie Creek Group.
The Grès à Voltzia is a geologic formation in France. It preserves fossils dating back to the Triassic period, more specifically the Anisian stage of the Middle Triassic epoch. It represents a lagerstatte that is well known for its palaeoflora, which shares numerous similarities with palaeobotanical assemblages in the Iberian Peninsula.
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