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The Pleistocene is the geological epoch that lasted from c. 2.58 million to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek πλεῖστος (pleîstos) 'most' and καινός 'new'.
Smilodon is a genus of felids belonging to the extinct subfamily Machairodontinae. It is one of the best known saber-toothed predators and prehistoric mammals. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats. Smilodon lived in the Americas during the Pleistocene epoch. The genus was named in 1842 based on fossils from Brazil; the generic name means "scalpel" or "two-edged knife" combined with "tooth". Three species are recognized today: S. gracilis, S. fatalis, and S. populator. The two latter species were probably descended from S. gracilis, which itself probably evolved from Megantereon. The hundreds of specimens obtained from the La Brea Tar Pits in Los Angeles constitute the largest collection of Smilodon fossils.
The La Brea Tar Pits is an active paleontological research site in urban Los Angeles. Hancock Park was formed around a group of tar pits where natural asphalt has seeped up from the ground for tens of thousands of years. Over many centuries, the bones of trapped animals have been preserved. The George C. Page Museum is dedicated to researching the tar pits and displaying specimens from the animals that died there. La Brea Tar Pits is a registered National Natural Landmark.
The dire wolf is an extinct canine. The dire wolf lived in the Americas during the Late Pleistocene and Early Holocene epochs. The species was named in 1858, four years after the first specimen had been found. Two subspecies are recognized: Aenocyon dirus guildayi and Aenocyon dirus dirus. The largest collection of its fossils has been obtained from the Rancho La Brea Tar Pits in Los Angeles.
The Chibanian, more widely known as Middle Pleistocene, is an age in the international geologic timescale or a stage in chronostratigraphy, being a division of the Pleistocene Epoch within the ongoing Quaternary Period. The Chibanian name was officially ratified in January 2020. It is currently estimated to span the time between 0.770 Ma and 0.129 Ma, also expressed as 770–126 ka. It includes the transition in palaeoanthropology from the Lower to the Middle Paleolithic over 300 ka.
The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently defined as the time between c. 129,000 and c. 11,700 years ago. The late Pleistocene equates to the proposed Tarantian Age of the geologic time scale, preceded by the officially ratified Chibanian. The beginning of the Late Pleistocene is the transition between the end of the Penultimate Glacial Period and the beginning of the Last Interglacial around 130,000 years ago. The Late Pleistocene ends with the termination of the Younger Dryas, some 11,700 years ago when the Holocene Epoch began.
Bison latifrons, also known as the giant bison or long-horned bison, is an extinct species of bison that lived in North America during the Late Pleistocene epoch ranging from southern Canada to Mexico. It is noted for large body size and its distinctive long horns.
The Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 4,750,000 to 1,806,000 years BP, a period of 2.944 million years. It is usually considered to start in the early-mid Pliocene Epoch and end by the early Pleistocene. The Blancan is preceded by the Hemphillian and followed by the Irvingtonian NALMA stages.
Armbruster's wolf is an extinct species that was endemic to North America and lived during the Irvingtonian stage of the Pleistocene epoch, spanning from 1.9 Mya—250,000 years BP. It is notable because it is proposed as the ancestor of one of the most famous prehistoric carnivores in North America, the dire wolf, which replaced it.
In paleontology, biochronology is the correlation in time of biological events using fossils. In its strict sense, it refers to the use of assemblages of fossils that are not tied to stratigraphic sections. Collections of land mammal ages have been defined for every continent except Antarctica, and most are correlated with each other indirectly through known evolutionary lineages. A combination of argon–argon dating and magnetic stratigraphy allows a direct temporal comparison of terrestrial events with climate variations and mass extinctions.
Tremarctos floridanus is an extinct species of bear in the family Ursidae, subfamily Tremarctinae. T. floridanus became extinct at the end of the last ice age, 11,000 years ago. It's fossils have been found throughout the Southeastern United States, in northeastern Mexico, and in Belize from the Rancholabrean epoch, and from earlier epochs at some sites in western North America.
Paramylodon is an extinct genus of ground sloth of the family Mylodontidae endemic to North America during the Pliocene through Pleistocene epochs, living from around ~4.9 Mya–12,000 years ago.
Arctodus is an extinct genus of short-faced bear that inhabited North America during the Pleistocene. There are two recognized species: the lesser short-faced bear and the giant short-faced bear. Of these species, A. simus was larger, is known from more complete remains, and is considered one of the most charismatic of North America's megafauna. A. pristinus was largely restricted to the Early Pleistocene of the eastern United States, whereas A. simus had a broader range, with most finds being from the Late Pleistocene of the United States, Mexico and Canada. A. simus evolved from A. pristinus, but both species likely overlapped in the Middle Pleistocene. Both species are relatively rare in the fossil record.
The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals and were established using geographic place names where fossil materials were obtained.
The Irvingtonian North American Land Mammal Age on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), spanning from 1.8 million – 250,000 years BP. Named after an assemblage of fossils from the Irvington District of Fremont, California, the Irvingtonian is usually considered to overlap the Lower Pleistocene and Middle Pleistocene epochs. The Irvingtonian is preceded by the Blancan and followed by the Rancholabrean NALMA stages.
The Clarkforkian North American Stage, on the geologic timescale, is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 56,800,000 to 55,400,000 years BP lasting 1.4 million years.
The Puercan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), spanning the interval from 66,000,000 to 63,300,000 years BP lasting 2.7 million years.
The Port Kennedy Bone Cave is a limestone cave in the Port Kennedy section of Valley Forge National Historical Park, Pennsylvania, USA. The Bone Cave "contained one of the most important middle Pleistocene fossil deposits in North America".
A list of prehistoric and extinct species whose fossils have been found in the La Brea Tar Pits, located in present-day Hancock Park, a city park on the Miracle Mile section of the Mid-Wilshire district in Los Angeles, California.
Capromeryx was a genus of dwarf pronghorns (Antilocapridae) that originated in North America during the Pliocene about 5 million years ago. The closest living relative and only surviving member of the family is the North American pronghorn.
References
- ↑ Sanders, A.E., R.E. Weems, and L.B. Albright III (2009) Formalization of the mid-Pleistocene "Ten Mile Hill beds" in South Carolina with evidence for placement of the Irvingtonian–Rancholabrean boundary, Museum of Northern Arizona Bulletin 64:369-375
- ↑ Savage, D.E. (1951) Late Cenozoic vertebrates of the San Francisco Bay region, University of California Publications, Bulletin of the Department of Geological Sciences 28:215-314
- ↑ Froese, Duane; Stiller, Mathias; Heintzman, Peter D.; Reyes, Alberto V.; Zazula, Grant D.; Soares, André E. R.; Meyer, Matthias; Hall, Elizabeth; Jensen, Britta J. L.; Arnold, Lee J.; MacPhee, Ross D. E.; Shapiro, Beth (2017-03-28). "Fossil and genomic evidence constrains the timing of bison arrival in North America". Proceedings of the National Academy of Sciences. 114 (13): 3457–3462. Bibcode:2017PNAS..114.3457F. doi: 10.1073/pnas.1620754114 . ISSN 0027-8424. PMC 5380047 . PMID 28289222.
- ↑ Barnosky, Anthony D; Holmes, Michael; Kirchholtes, Renske; Lindsey, Emily; Maguire, Kaitlin C; Poust, Ashley W; Stegner, M Allison; Sunseri, Jun; Swartz, Brian; Swift, Jillian; Villavicencio, Natalia A (2014-12-01). "Prelude to the Anthropocene: Two new North American Land Mammal Ages (NALMAs)". The Anthropocene Review. 1 (3): 225–242. Bibcode:2014AntRv...1..225B. doi:10.1177/2053019614547433. ISSN 2053-0196.
- ↑ Paleobiology Database, Sheridanian substage