The geologic column of the nearby Taylorsville region shows the Hosselkus Limestone as 140 ft thick and of Late Triassic (early Karnian) age. It is well exposed near the Cosmopolitan mine on the divide between the Genesee Valley and Hosselkus Creek. It has been recognized at numerous outcrops between Spanish Ranch and Prattville and northwestward beyond Pit River in the Klamath Mountains, and is considered to be younger than the Swearinger slates and older than the Trail beds. It contains numerous Arcestes and abundant pentagonal crinoid stems which indicate it is of Late Triassic age.[2]
Paleofauna
Over 208 described species of invertebrates have been found in the Hosselkus Limestone and nearby Brock Mountain.[3] These species include shellfish, nautilus, snails, and ammonites. Many of these species can be also found in the Mediterranean region, which shows a much closer connection between the American and Mediterranean regions. The Great Basin sea was then the western end of the ancient Tethys, of which the Indian sea was the eastern limit.
The Early Jurassic Epoch is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic–Jurassic extinction event, 201.3 Ma, and ends at the start of the Middle Jurassic 174.7 ±0.8 Ma.
The Carnian is the lowermost stage of the Upper Triassic Series. It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by the Norian. Its boundaries are not characterized by major extinctions or biotic turnovers, but a climatic event occurred during the Carnian and seems to be associated with important extinctions or biotic radiations. Another extinction occurred at the Carnian-Norian boundary, ending the Carnian age.
Shonisaurus is a genus of very large ichthyosaurs. At least 37 incomplete fossil specimens of the marine reptile have been found in the Luning Formation of Nevada, USA. This formation dates to the late Carnian age of the late Triassic period, about 237–227 million years ago.
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.
Arcestes is a genus of extinct ceratitid ammonites found in Triassic-aged marine strata.
Californosaurus is an extinct genus of ichthyosaur, an extinct marine reptile, from the Lower Hosselkus Limestone of California, and also the Muschelkalk of Germany.
Omphalosaurus is an extinct genus of marine reptile from the Early Triassic to Middle Triassic, thought to be in the order of Ichthyosauria. Most of what is known about Omphalosaurus is based on multiple jaw fragments, ribs, and vertebrae. Specimens of Omphalosaurus have been described from the western United States, Poland, Austria and the island of Spitsbergen off the northern coast of Norway.
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.
La Bocana Roja Formation is a geological formation in Baja California, Mexico whose strata date back to the Late Cretaceous, specifically around the Cenomanian to Turonian. Dinosaur remains are among the fossils that have been recovered from the formation.
The Aztec Sandstone is an Early Jurassic geological formation of primarily eolian sand from which fossil pterosaur tracks have been recovered. The formation is exposed in the Mojave Desert of Arizona, California and Nevada. Aztec Sandstone is named after the Aztec Tank, a lake in the Spring Mountain region of Nevada.
Toretocnemus is an extinct genus of ichthyosaur. Its remains have been found in California, United States, in Triassic layers of the Carnian Hosselkus Limestone.
The Chico Formation is a geologic formation of the Campanian Age during the Cretaceous Period, found in California and southern Oregon.
The Ladd Formation is a Mesozoic geologic formation located in Orange County, California.
The Moreno Formation is a Mesozoic geologic formation located in San Joaquin Valley (California). Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.
Reptiles arose about 320 million years ago during the Carboniferous period. Reptiles, in the traditional sense of the term, are defined as animals that have scales or scutes, lay land-based hard-shelled eggs, and possess ectothermic metabolisms. So defined, the group is paraphyletic, excluding endothermic animals like birds that are descended from early traditionally-defined reptiles. A definition in accordance with phylogenetic nomenclature, which rejects paraphyletic groups, includes birds while excluding mammals and their synapsid ancestors. So defined, Reptilia is identical to Sauropsida.
The Doswell Formation is a geologic unit of Upper Triassic age, part of the Newark Supergroup. The Doswell Formation was originally named to refer to a geological sequence which forms the lower part of the sedimentary fill of the Taylorsville Basin in Virginia and Maryland. This sequence was deposited by lakes and rivers in the developing rift basin. A 2016 study argued that several geological layers in Pennsylvania as well as the neighboring Richmond Basin of Virginia also qualified as components of the Doswell Formation.
Paleontology in California refers to paleontologist research occurring within or conducted by people from the U.S. state of California. California contains rocks of almost every age from the Precambrian to the Recent.
The geological history of North America comprises the history of geological occurrences and emergence of life in North America during the interval of time spanning from the formation of the Earth through to the emergence of humanity and the start of prehistory. At the start of the Paleozoic Era, what is now "North" America was actually in the Southern Hemisphere. Marine life flourished in the country's many seas, although terrestrial life had not yet evolved. During the latter part of the Paleozoic, seas were largely replaced by swamps home to amphibians and early reptiles. When the continents had assembled into Pangaea, drier conditions prevailed. The evolutionary precursors to mammals dominated the country until a mass extinction event ended their reign.
The Xiaowa Formation is a Carnian-age geological formation found in southern China. It is a sequence of limestone and marls from the Carnian stage of the Triassic. Its lower section was previously known as the Wayao Formation or Wayao Member of the Falang Formation. In 2002, the Wayao Member was renamed and raised to the Xiaowa Formation to prevent confusion with an Eocene unit of the same name. Crinoids and marine reptiles are abundant in the Xiaowa Formation, forming a lagerstätte known as the Guanling biota. Ammonoids and conodonts found in the formation constrain its age to the early Carnian. Reptiles of the Guanling biota include ichthyosaurs, thalattosaurs, placodonts, and Odontochelys. Sedimentary events within this formation have been tied to the Carnian Pluvial Event.
The Saurian Expedition of 1905 was a paleontological research mission in northern Nevada in the United States. The expedition recovered many of the most well-preserved specimens of ichthyosaur ever found. Information on the key contributors, details on the expedition itself and its findings can be found below.
1 2 3 4 5 6 "Appendix: Summary of the Mesozoic Reptilian Fossils of California," in Hilton (2003) p. 267
↑ "Appendix: Summary of the Mesozoic Reptilian Fossils of California," in Hilton (2003) pp. 265-267
↑ "Appendix: Summary of the Mesozoic Reptilian Fossils of California," in Hilton (2003) pp. 266-267
↑ "Appendix: Summary of the Mesozoic Reptilian Fossils of California," in Hilton (2003) pp. 267-270
1 2 3 4 5 "Appendix: Summary of the Mesozoic Reptilian Fossils of California," in Hilton (2003) p. 270
1 2 3 4 "4: The Marine Reptiles; Triassic Ichthyosaurs; Shastasauria," in Hilton (2003) p. 88.
1 2 3 "4: The Marine Reptiles; Triassic Ichthyosaurs; Shastasauria," in Hilton (2003) p. 88. Misspelled as "Shonosaurus" in "Appendix: Summary of the Mesozoic Reptilian Fossils of California," Hilton (2003) p. 270
1 2 "Appendix: Summary of the Mesozoic Reptilian Fossils of California," in Hilton (2003) p. 270-271
External links
Hilton, Richard P. (2003). Dinosaurs and Other Mesozoic Reptiles of California. Berkeley: University of California Press. ISBN9780520928459. 318 pp.
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