The Irvingtonian North American Land Mammal Age on the
geologic timescale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochr ...
is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), spanning from 1.9 million – 250,000 years BP.The _Blancan, Irvingtonian and Rancholabrean Mammal Ages by Christopher J. Bell and Ernest L. Lundelius Jr., Anthony D. Barnosky, Russell W. Graham, Everett H. Lindsay, Dennis R. Ruez Jr., Holmes A. Semken Jr., S. David Webb, and Richard J. Zakrzewski. January 2004 in the book: Late Cretaceous and Cenozoic Mammals of North America: Biostratigraphy and Geochronology. Chapter: 7. Publisher: Columbia University Press; Editors: Michael O. Woodburne. pp274-276 Named after an assemblage of fossils from the Irvington District of Fremont, California, (1951) Late Cenozoic vertebrates of the San Francisco Bay region, ''University of California Publications, Bulletin of the Department of Geological Sciences'' 28:215-314 the Irvingtonian is usually considered to overlap the Lower Pleistocene and Middle Pleistocene epochs. The Irvingtonian is preceded by the
Blancan
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 .Rancholabrean
NALMA
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 (or stages when ref ...
stages.
The Irvingtonian can be further divided into substages:
*Irvingtonian I - approximately 1.9 MA TO 0.85 MA
*Irvingtonian II - approximately 0.85 MA TO 0.4 MA
*Irvingtonian III - approximately 0.4 MA TO 0.25 MA
The beginning of the Irvingtonian is defined by the first appearance of '' Mammuthus'' south of 55° N in North America, and the beginning of the succeeding Rancholabrean is defined by the first appearance of ''
Bison
Bison are large bovines in the genus ''Bison'' (Greek: "wild ox" (bison)) within the tribe Bovini. Two extant and numerous extinct species are recognised.
Of the two surviving species, the American bison, ''B. bison'', found only in North A ...
''.
In South America, it chronologically overlaps with the Uquian (partial),
Ensenadan
The Ensenadan age is a period of geologic time (1.2–0.8 Ma) within the Early Pleistocene epoch of the Quaternary used more specifically with South American Land Mammal Ages. It follows the Uquian and precedes the Lujanian
The Lujanian age is a ...
Hesperocyoninae
The extinct Hesperocyoninae are one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Borophaginae and extant Caninae.
Taxonomic history
Hesperocyoninae are basal canids that gave rise to the o ...
Hypolagus
''Hypolagus'' is an extinct genus of lagomorph, first recorded in the Hemingfordian (early to middle Miocene) of North America. It entered Asia during the early Turolian and spread to Europe not much later, where it survived until the Middle Ple ...
Plesippus
''Plesippus'' is a genus of extinct horse from the Pleistocene of North America. Although commonly seen as a subgenus of ''Equus'' recent cladistic analysis considers it a distinct genus.
Species
Two species are recognized by Barron et al. (201 ...
Rhynchotherium
''Rhynchotherium'' is an extinct genus of proboscidea endemic to North America and Central America during the Miocene through Pliocene from 13.650 to 3.6 Ma, living for approximately .
This gomphothere had two tusks and may have evolved fr ...
'', gomphotheres
* ''
Stegomastodon
''Stegomastodon'' ('roof breast tooth') is an extinct genus of gomphotheres, a family of proboscideans. It ranged throughout North America from the early Blancan ~4 Ma, to the early Irvingtonian (~1.2 Ma). The South American species have been ...
'', gomphotheres
Rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...
Charadriiformes
Charadriiformes (, from ''Charadrius'', the type genus of family Charadriidae) is a diverse order of small to medium-large birds. It includes about 390 species and has members in all parts of the world. Most charadriiform birds live near water a ...
turnstone
Turnstones are two bird species that comprise the genus ''Arenaria'' in the family Scolopacidae. They are closely related to calidrid sandpipers and might be considered members of the tribe Calidriini.
The genus ''Arenaria'' was introduced by ...