Английская Википедия:Blancan

Содержание

Текст

Текст

Текст

Текст

Текст

Текст

Текст

Текст

Текст

Шаблон:Short description 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 Шаблон:Mya. 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.

As usually defined, it corresponds to the mid-Zanclean through Piacenzian and Gelasian stages in Europe and Asia. In California, the Blancan roughly corresponds to the mid-Delmontian through Repettian and Venturian to the very early Wheelerian. The Australian contemporary stages are the mid-Cheltenhamian through Kalimnan and Yatalan. In New Zealand, the Opoitian starts at roughly the same time and the Blancan is further coeval with the Waipipian and Mangapanian stages to the early Nukumaruan. Finally, in Japan the Blancan starts coeval with the late Yuian, runs alongside the Totomian and Suchian and ends soon after the start of the Kechienjian.

Dating issues

The start date of the Blancan has not been fully established. There is general agreement that it is between 4.9 and 4.3 mya (million years ago). The often-cited GeoWhen database places it at 4.75 mya.

There is even stronger disagreement about the end of the Blancan. Some stratigraphers argue for the 1.808 mya date that corresponds better with the end of the Pliocene and the start of the Pleistocene (1.808 mya). This conforms with the extinction of Borophagus, Hypolagus, Paenemarmota, Plesippus, Nannippus, and Rhynchotherium faunal assemblage between 2.2 and 1.8 mya. Other paleontologists find continuity of the faunal assemblages well into the Pleistocene, and argue for an end date of 1.2 mya. This corresponds with the extinction of stegomastodons and related species and the appearance of mammoths in southern North America.

Fauna

The middle of the Blancan, about 2.7 mya, is when the land bridge connection between North and South America was reestablished and taxa like sloths and glyptodonts appeared in North America at the height of the Great American Interchange.

Notable mammals

Artiodactyla – even-toed ungulates

• Platygonus, peccaries

Carnivora – carnivores

• Arctotherium?, giant short-faced bear
• Hesperocyoninae, dog-like carnivores
• Borophagus, bone-crushing dogs
• Canis, wolves
• Chasmaporthetes, hyenas
• Smilodon, saber-toothed cat
• Homotherium, saber-toothed cat
• Xenosmilus, saber-toothed cat

Lagomorpha – lagomorphs

• Hypolagus, rabbits

Perissodactyla – odd-toed ungulates

• Nannippus, horses
• Plesippus, horses – may belong into Equus
• Equus giganteus

Proboscidea

• Rhynchotherium, gomphotheres
• Stegomastodon, gomphotheres

Rodentia – rodents

• Paenemarmota, giant marmots

Xenarthra

• Glyptotherium, giant armadilloШаблон:Col-2-of-2

Notable birds

Cathartidae – New World vultures

• Sarcoramphus kernense, Kern Vulture

Charadriiformes

• unknown scolopacid (archaic calidrid or turnstone?)

Falconiformes – diurnal raptors

• Falco sp., a falcon

Passeriformes

• unknown corvid (archaic magpie?)

See also

• Mount Blanco

Further reading

• Lourens, L. et al. (2004): The Neogene Period. In: Gradstein, F.; Ogg, J. & Smith, A.G. (eds.): A Geologic Time Scale 2004. Cambridge University Press. Шаблон:ISBN
• Шаблон:Cite journal

Шаблон:Neogene Footer Шаблон:Quaternary Footer