Irvingtonian Explained

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.^{[1] [2]} Named after an assemblage of fossils from the Irvington District of Fremont, California,^[3] 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 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^[1]

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.^[4]

In South America, it chronologically overlaps with the Uquian (partial), Ensenadan, and Lujanian in South American Land Mammal Ages.

Fauna

Notable mammals

Artiodactyla - even-toed ungulates

• Platygonus, peccaries
• Titanotylopus, camels

Carnivora - carnivores

• Borophagus, bone-crushing dogs
• Canis, wolves
• Chasmaporthetes, hyenas
• Machairodontinae, saber-toothed cats
• Lynx, lynxes, bobcats
• Ursus, bears

Lagomorpha - lagomorphs

• Hypolagus, rabbits

Perissodactyla - odd-toed ungulates

• Nannippus, horses
• Plesippus, horses - may belong in Equus

Proboscidea - elephants

• Elephantidae, mammoths
• Mammutidae, mastodons
• Rhynchotherium, gomphotheres
• Stegomastodon, gomphotheres

Rodentia - rodents

• Paenemarmota, giant marmots

Notable birds

Charadriiformes

• unknown scolopacid (archaic calidrid or turnstone?)^[5]

Falconiformes - diurnal raptors

• Falco sp., a falcon^[6]

Passeriformes

• unknown corvid (archaic magpie?)

Notes and References

1. https://www.researchgate.net/publication/263425514_The_Blancan_Irvingtonian_and_Rancholabrean_Mammal_Ages The _Blancan, Irvingtonian and Rancholabrean Mammal Ages
2. Smith . Gregory James . DeSantis . Larisa R. G. . February 2020 . Extinction of North American Cuvieronius (Mammalia: Proboscidea: Gomphotheriidae) driven by dietary resource competition with sympatric mammoths and mastodons . Paleobiology . en . 46 . 1 . 41–57 . 10.1017/pab.2020.7 . 0094-8373.
3. (1951) Late Cenozoic vertebrates of the San Francisco Bay region, University of California Publications, Bulletin of the Department of Geological Sciences 28:215-314
4. Web site: Irvingtonian North American Land Mammal Age. 2017-03-28. Florida Museum. en-US. 2020-04-24.
5. Wetmore (1937)
6. Feduccia (1970)