The Orellan is a North American Land Mammal Age typically set from around 33,700,000 to 32,000,000 years BP , a period of 1.7 million years . The Orellan is preceded by the Chadronian and followed by the Whitneyan NALMA stages. Relative to global geological chronology (the geologic time scale ), it is usually considered to fall within the earliest part (early Rupelian stage) of the Oligocene epoch, beginning around the same time as the Eocene -Oligocene boundary.
11-952: The Orellan is named after the Orella Member of the Brule Formation , a widespread subunit of the White River Group . The Orella Member crops out most extensively in northwest Nebraska and eastern Wyoming . In the White River badlands of southwest South Dakota , an equally extensive Orellan component of the Brule Formation is known as the Scenic Member. Orellan strata of the Brule Formation can be found in more restricted exposures across northeast Colorado (Cedar Creek Member) and North Dakota . Certain sites in Montana preserve Orellan mammals:
22-559: A clade of Cariamiformes outside of a clade including seriemas and phorusrhacids , as well as a possible European specimen. Paracrax and Eutreptornis are understood to be odd taxa whose cariamiform affinities are not fully resolved. A 2024 study however finds Bathornis as closer to seriemas than phorusrhacids were. Though some forms like Paracrax wetmorei might have been capable of flight, most taxa were flightless, constituting examples of flightless birds in mammal dominated environments. Paracrax gigantea , Paracrax antiqua and
33-453: Is 320 ft. Has not been recognized E. of long. 101°30', where it appears to sink beneath the surface In Platte Valley. Extends far to NB. in So. Dak. Is upper fm. of White River group." N. H. Darton, 1898 (D, 8, G, S, 19th Ann, Eept., p t 4, pp. 736, 766–759). (Abbreviations are in source document.) The sandstones layers, which are up to 3 metres (9.8 ft) thick, can contain mammalian fossils (e.g.
44-602: Is a stub . You can help Misplaced Pages by expanding it . Bathornithidae Bathornithidae is an extinct family of birds from the Eocene to Miocene of North America . Part of Cariamiformes , they are related to the still extant seriemas and the extinct Phorusrhacidae . They were likely similar in habits, being terrestrial, long-legged predators, some of which attained massive sizes. It has been suggested that most, if not all, North American Paleogene cariamiforme fossils are part of this group. Storrs Olson also referred
55-765: Is a sequence of fine grained clastic rocks ( claystones , mudstones , siltstones ) interbedded with freshwater carbonates, volcanic ash ( tuff ), and sandstone . The formation was named by N. H. Darton "for the Brule Indians, who once roamed over Pine Rldge Ind. Res. in southern S. Dak., where the fm. covers large areas, and that it is not present in Brule Ind. Res., which occurs farther NE In S. Dak." Darton's first description stated, "The White River beds In their extension from S. Dak. Into Nebr. present some differences in strat. range and relations. They expand considerably and include, at top, beds which appear not to be represented in
66-817: The Dunbar Creek Formation and the Cook Ranch and Matador Ranch local faunas of the Cook Ranch Formation . The Byram Formation of Mississippi also appears to be Orellan. The beginning of the Orellan is defined by the first appearance of Hypertragulus calcaratus (a hypertragulid ruminant ). Other mammals which first appear at the start of the stage include Leptomeryx evansi (a leptomerycid ruminant) and Palaeolagus intermedius (an early lagomorph ). Poebrotherium eximium (an early camelid ) and Miohippus grandis (an early horse) last appear around
77-628: The Paleogene period is a stub . You can help Misplaced Pages by expanding it . This article about a specific stratigraphic formation in Nebraska is a stub . You can help Misplaced Pages by expanding it . This article about a specific stratigraphic formation in North Dakota is a stub . You can help Misplaced Pages by expanding it . This article about a specific stratigraphic formation in South Dakota
88-490: The European Elaphrocnemus to this clade, though it has since been rejected. Conversely, some analysis have instead recovered them as a polyphyletic group, with Bathornis and kin being sister taxa to phorusrhacids while Paracrax is rendered closer to modern seriemas, though this assessment is heavily debated. The most recent consensus is that Bathornithidae is relegated exclusively to Bathornis , as
99-560: The Fitterer bed). The most important fossils sites are: Prehistoric catfish , several mammals such as nimravids and Hesperocyon , and sunfish fossils are known from the Brule Formation in Badlands National Park . Notable among the local fauna are Bathornithid birds, ranging from the highly varied wetland-dwelling Bathornis species to the gigantic Paracrax . Proscalops This article related to
110-553: The base of the Orellan, and brontotheres go extinct only shortly above the base. This geochronology article is a stub . You can help Misplaced Pages by expanding it . Brule Formation The Brule Formation was deposited between 33 and 30 million years ago, roughly the Rupelian age ( Oligocene ). It occurs as a subunit of the White River Group in South Dakota , Nebraska , Colorado , North Dakota , and Wyoming . It
121-491: The typical regions. Accordingly, to afford distinct definitions for the members in Nebr. I have Introduced the designation Brule clay and separated the underlying Titanotherium beds as Chadron fm. The Brule consists mainly of a hard, sandy clay, of pale-pink color. Thickness about 600 ft. In vicinity of Wyo. line, but diminishes greatly eastward; in vicinity of 103° mer. in NW. comer of Nebr. it
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