How to use Oligocene in a sentence
This ocean, already diminished in area, retreated after Oligocene times from the Iranian plateau, Turkestan, Asia Minor and the region of the north-west Alps.
Fossil remains of members of this family have also been found in Europe in strata of the Oligocene period.
From the Oligocene deposits of France and southern England have been obtained numerous remains of opossums referable to the American family Didelphyidae.
In this valley were laid down, either in Eocene or Oligocene times, a great series of lake beds and thick accumulations of brown coal.
Oligocene Elornis and, allied, Palaelodus.Advertisement
Coming to the Tertiary we find the Oligocene beds of Aix, of east Prussia (amber) and of Colorado, and the Miocene of Bavaria, especially rich in remains of beetles, most of which can be referred to existing genera.
The connecting link with Hyracotherium was formed by Pachynolophus (Pro palaeotherium), and the line apparently terminated in Palo plotherium, which is also Oligocene.
Mayr and others, while Scudder has studied the rich Oligocene faunas of Colorado (Florissant) and Wyoming (Green River).
Remains of spiders from the Baltic amber beds of Oligocene age and from nearly coeval fluviatile or lacustrine deposits of North America belong to forms identical with or closely related to existing genera, thus proving the great antiquity of our present spider fauna.
Finally, in the Oligocene Colodon the last three upper premolars are like the molars, and the first pair of lower incisors is lost.Advertisement
The most primitive group is that of the American Hyracodontidae, !represented in the Oligocene by Hyrachyus, Hyracodon and Triplopus.
In the Lower Oligocene of Europe we have Ronzotherium and in that of America Leptaceratherium (Trigonias), which were primitive species with persistent upper canines and three-toed fore-feet.
Possibly they belonged to the Amynodontidae, but they may have been related to the Upper Oligocene Diceratherium, in which the nasal bones formed a transverse pair; this genus being common to Europe and North America.
Hornless rhinoceroses, with five fronttoes, ranging from the Oligocene to the Lower Pliocene in Europe, represent the genus Aceratherium, which may also occur in America, as it certainly does in India.
The latter, like the similar deposits in other West Indian islands, is probably of Oligocene age.Advertisement
The shells which have been found in them indicate that they belong for the most part to the Oligocene period.
No noteworthy fossil spiders are known; the best-preserved are in amber of Oligocene age.
The flat summit is formed by a succession of limestones - all deposited in shallow water - from the Eocene (or Oligocene) up to recent deposits in the above-mentioned atoll with islands on its reef.
Jukes-Browne and Harrison ascribe the Scotland beds to the Eocene or Oligocene period, the Oceanic series to the Miocene, the Bissex Hill marls to the Pliocene, and the coral limestones partly to the Pliocene and partly to the Pleistocene.
The Oligocene and Miocene formations are present, but the Upper Miocene is confined to the coast.Advertisement
Geologically they are known to date back to the Oligocene period, and wings believed to be referable to them have been found in Liassic and Jurassic beds.
The Lower Limestone probably belongs to the Tongarian stage of the Oligocene series, and the Upper Coralline Limestone to the Tortonian stage of the Miocene.
It includes the two families Anoplotheriidae and Dichobunidae, of which the first died out with the Oligocene, while the second may have given origin to the Tragulina and perhaps the Pecora.
The most interesting genera are, however, the Upper Oligocene and Lower Miocene Gelocus and Prodremotherium, which have perfectly selenodont teeth, and the third and fourth metacarpal and metatarsal bones respectively fused into an imperfect cannon-bone, with the reduction of the lateral metacarpals and metatarsals to mere remnants of their upper and lower extremities.
The genus has a very wide distribution, extending from Europe through Asia to North America, and occurring in strata which are of Oligocene and Miocene age.Advertisement
In the above genera, so far as is known, the feet were four-toed, although with the lateral digits relatively small; but in Elotherium (or Entelodon), from the Lower Miocene of Europe and the Oligocene of North America, the two lateral digits in each foot had disappeared.
Tapirs are an ancient group with many of the original characters of the primitive Ungulates of the Oligocene period, and have undergone but little change since the Miocene.
The Cainozoic system is represented by Oligocene, Miocene, Pliocene and Pleistocene beds.
In southern Otago the Oligocene beds are brown coals and lignites with oil shales, which, at Orepuki, contain 47% of oil and gas, with 8% of water.
The Cainozoic volcanic history of New Zealand begins in the Oligocene, when the high volcanic domes of Dunedin and Banks Peninsula were built up. The Dunedin lavas including tephrites and kenytes correspond to the dacite eruptions in the volcanic history of Victoria.
The Eocene beds are nummulitic. There is a lacustrine group which has usually been placed in the Lower Eocene, but the discovery of Anthracotherium magnum in the interbedded lignites proves it to be Oligocene, in part at least.
The Oligocene period consists of a marine phase confined to the littoral zone of Kabylia, and of a continental phase occupying vast areas composed of lacustrine, alluvial, gypsiferous marls, sandstones and conglomerates.
Rhineura of Florida, and also known from the Oligocene of South Dakota; Lepidosternum of South America; and Anops in America and Africa; Blanus cinereus, Mediterranean countries.
This classification is based almost wholly on the fossils, for there seems to be little physical reason for the differentiation of the Oligocene anywhere on the continent.
The oil of Texas and Louisiana is from the Miocene (or possibly Oligocene) dolomite.
In the European Miocene we have Hyotherium and Palaeochoerus, and in the Upper Oligocene Propalaeochoerus, which have square molars without any tendency to a selenodont structure in their cusps.
Choeropotamus is a European Oligocene genus with bunodont molars which show a conspicuous basal cingulum in the lower dentition; the first premolar is absent.
In the European Miocene Listriodon, which also occurs in the Indian Tertiaries, the molars have a pair of transverse ridges, like those of the proboscidean Dinotherium; but the genus is believed to be related to the Oligocene Doliochoerus and Choerotherium, in which these teeth show a more normal type of structure.
For the genus Elotherium, of the Lower Miocene and Upper Oligocene of both hemispheres, which is often placed next the Suidae, see ARTIODACTYLA.
The Psocidae themselves have not been traced back beyond the Oligocene, in the amber of which period their remains are fairly numerous.
A more advanced phase is represented in the European Lower Oligocene by the Pseudosciuridae, with the genera Pseudosciurus, Sciuroides, Trechomys, Theridomys, &c., in which part of the masseter passes through the broad infra-orbital canal, and the premolars are; the molars being low-crowned, many-rooted and either cusped or ridged.
In the highly specialized mastoid region of the skull, the North American Oligocene Protoptychus approaches to Dipopodomys, while the contemporary Gymnoptychus and Entoptychus likewise appear referable to the Geomyidae.
The Upper Oligocene Cricetodon in Europe and Eumys in America are the earliest known forerunners of the cricetine Muridae; while at the same time primitive beavers appear in the form of Steneofiber, to be succeeded in the European Pleistocene by the gigantic Trogontherium.
In contradistinction to Titanomys, in which the cheek-teeth are rooted, is the North American Upper Oligocene Palaeolagus, where they are rootless.
Remains of several of the existing genera have been found in Oligocene and later beds of Europe, Sumatra and North America.
From this it may be inferred that the ancestral peccaries entered America in the Upper Oligocene.
The Molasse, in the neighbourhood of the mountains, consists chiefly of conglomerates and sandstones, and the Flysch consists of sandstones and shales; but the Molasse is of Miocene and Oligocene age, while the Flysch is mainly Eocene.
Except in Limburg, where, in the neighbourhood of Maastricht, the upper layers of the chalk are exposed and followed by Oligocene and Miocene beds, the whole of Holland is covered by recent deposits of considerable thickness, beneath which deep borings have revealed the existence of Pliocene beds similar to the " Crags " of East Anglia.
The Oligocene forms a band stretching from Antwerp to Maastricht, and this is followed towards the north by a discontinuous strip of Miocene and a fairly extensive area of Pliocene.
The Eoccne system is unknown in Germany except in the foothills of the Alps; but the Oligocene and Miocene are widely spread, especially in the great plain and in the depression of the Danube.
The Eocene and Oligocene form a broad belt along the northern coast, very much more continuous than the Mesozoic band, and from this belt a branch extends southwards to Sciacca.
The fluvio-marine deposits of the Upper Eocene and Oligocene formations contain an interesting mammalian fauna, proving that the African continent formed a centre of radiation for the mammalia in early Tertiary times.
Titanotherium, of the Oligocene of the Dakotas and neighbouring districts, was a huge beast, with the hinder upper premolars similar in character to the molars, a pair of horn-cores, arising from the maxilla, overhanging the nose-cavity, four front and three hind toes, only twenty dorso-lumbar vertebrae, and an almost continuous and unbroken series of teeth, in which the canines are short; the dental formula being i.
As we descend in the geological series the deer have simpler antlers, as in the European Miocene Dicrocerus; while in the Oligocene Amphitragulus, Dremotherium and Palaeomeryx, constituting the family Palaeomerycidae, antlers were absent, and the crowns of the molars so low that the whole depth of the hollows between the crescentic columns is completely visible.
The presence of these fossils indicates that the eruptions were subaerial, and a comparison of them with those elsewhere found among Older Tertiary strata shows that they probably belong to the Oligocene stage of the Tertiary series of formations, and therefore that the basalt eruptions took place in early Tertiary time.
From the Mid-Miocene to the Oligocene of France are known several species of Palaelodus, Elornis and Agnopterus, which have relatively shorter legs, longer toes and a complicated hypotarsus, and represent an earlier family, less specialized although not directly ancestral to the flamingos.
Again, the remarkable horned North American Oligocene genus Protoceras, while displaying resemblances to Leptomeryx and Leptoreodon, presents also points of similarity to the Tragulina and Pecora (q.v.).
The family ranges in North America from the Upper Eocene to the Lower Miocene, but Oreodon (or Merycoidodon), which is typified by an animal of the size of a sheep, is Oligocene.
The Tertiary system includes conglomerates, sandstones, limestones and marls, which appear to be of Eocene, Oligocene and Miocene age.
Cretaceous limestones and serpentine take a large part in the formation of these mountains, while even the Oligocene is involved in the folds.
The Oligocene consists of grey and white marls (known as the Idalian series), which are distributed all over the island and attain their greatest development on the south side of the Troodos.
The volcanic rocks then formed are followed by marine deposits of Oligocene and Miocene age.
They include some Miocene, or perhaps Oligocene marine sands, formed in the northern part of an inland sea, which occupied the basin of the Lower Murray.
Again, in the Hampshire Basin and Isle of Wight, Eocene and Oligocene formations rest upon the Chalk.
In 1854 he proposed the term Oligocene for certain Tertiary strata intermediate between the Eocene and Miocene; and the term is now generally adopted.
The Jurassic and Cretaceous beds are ordinary marine sediments, but from the Cenomanian to the Oligocene the deposits are of the peculiar facies known in the Alps and Carpathians as Flysch.
Beginning with the earliest known lemur, Anaptomorphus, this genus shows tendencies towards the anthropoids, and, when we pass up into the Oligocene of the Old World, Adapis is a decidedly mixed type, and probably not far from the common stem-form which gave origin to both suborders of the Primates.
Elsewhere they occur in South America and throughout a large part of the northern hemisphere, where they appear to have survived in India to the later Oligocene or Miocene.
Near the latter locality, beds of Oligocene age have been noticed, consisting of coarse limestones.
Beyrich introduced the Oligocene period, and some geologists recognize a Palaeocene or early Eocene period.
The earth movements which raised the Pyrenees appear to have begun in the Eocene period, but it was in Oligocene times that the principal folding took place.
But the most extensive and interesting Tertiary accumulations are those of the great lakes which in Oligocene and Miocene time spread over so large an expanse of the table-land.
The superficial Miocene and Pliocene deposits in the west, above referred to, are underlaid by the White river groups of the Oligocene, whose outcrops of Brule clay and Chadron formation also have been mentioned.
It was once generally supposed that the Pliocene epoch in Nebraska was distinguished by the activity of geysers; but the so-called geyserite " now known commonly and correctly as " natural pumice " and " volcanic ash," which is found in the Oligocene and later formations, has no connexion whatever with geysers, but is produced by the shattering of volcanic rock.
The Cainozoic system includes at Table Cape an outcrop of marine beds probably of Oligocene age.
The Tertiary formations have been assigned to six periods; these are termed - Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and each has its own botanical peculiarities.
The British Eocene and Oligocene strata yield so large a flora, and contain plant-beds belonging to so many different stages, that it is unfortunate we have still no monograph on the subject, the one commenced by Ettingshausen and Gardner in 1879 having reached no farther than gocene 79 g Oli of Great the Ferns and Gymnosperms. This deficiency makes it impossible to deal adequately with the British Eocene plants, most of the material being either unpublished or needing re-examination.
The absence cf the so-called cinnamon-leaves and the Smilaceae, which always enter into the composition of Middle Eocene and Oligocene floras, is noticeable.
Leaving these Scottish and Irish deposits of doubtful age, we find in the Hampshire Basin a thick series of fluviatile, lacustrine and marine deposits undoubtedly of Lower and Middle Oligocene date.
The flora of Bovey is like that of the lignite of the Wetterau, which is either highest Oligocene or lowest Miocene.
The succeeding Oligocene flora appears to be more characterized by a gradual replacement of the Eocene species by allied fcrms, than by any marked change in the assemblage or in the climatic conditions.
Among the types of vegetation which make their appearance in Europe during the Oligocene period may be mentioned the Conifers Libocedrus salicornioides, several species of Chamaecyparis and Sequoia, Taxodium distichum and Glyptostrobus europaeus.
Though we do not propose to deal with the other European localities for Eocene and Oligocene plants, there is one district to which attention should be drawn, on account of the exceptional state of preservation of the specimens.
This is derived from strata of Oligocene age, and is particularly valuable because it preserves perfectly various soft parts of the plants, which are usually lost in fossil specimens.
No doubt this amber flora is still imperfectly known, but it is valuable as giving a good idea of the vegetation, during Oligocene times, of a mixed wood of pine and oak, in which there is a mixture of herbaceous and woody plants, such as would now be found under similar conditions.
From Europe it will be convenient to pass to a distant region of similar latitude, so that we may see to what extent botanical provinces existed in Eocene and Oligocene times.
Apart from a few unsatisfactory remains from the Eocene of Wyoming, fossil tailless batrachians are otherwise only known from the Oligocene, Miocene and Pliocene of Europe and India.
Nearly allied is the American Mesohippus, ranging from the Lower Miocene to the Lower Oligocene of the United States, of which the earliest species stood only about 18 in.
Fossil insects referable to the order have been found in Tertiary beds as old as the White River Oligocene of North America, and the Baltic amber, but nothing is known as to the previous history of the group.
The Baltic amber or succinite is found as irregular nodules in a marine glauconitic sand, known as "blue earth," occurring in the Lower Oligocene strata of Samland in East Prussia, where it is now systematically mined.
In many respects, especially the form of the lower jaw, Anthracotherium, which is of Oligocene and Miocene age in Europe, and typifies the family Anthracotheriidae, is allied to the hippopotamus, of which it is probably an ancestral form.
Generalized features are also displayed by the Oligocene Hypisodus, which in its short skull and large orbits presents a curious approximation to the African dik-dik antelopes of the genus Madoqua (see Antelope).
The earliest representatives of the Tylopoda according to Professor Scott is the Middle Eocene genus Homacodon, typifying the family Homacodontidae, which is regarded as the common ancestor of both Camelidae and Oreodontidae, with resemblances to the European Oligocene genus Dichobune (see Artiodactyla).