Datos demogrÃ¡ficos de Saint Vincent And The Grenadines

The Mesozoic (of the old Greek mesos: μεσο ), means and zoon: ζωον ), animal), called in the past “secondary era”, are a geological era which extends from - 251 with - 65,5 My, and during which appear species of Mammifère S and Dinosaure S.

Its higher limit corresponds to the Extinction of the Cretaceous.

Position of the continents

Geologically, at the beginning of Mesozoic, the totality of the emerged grounds was gathered in a Supercontinent, the Pangée. During this era, Pangée is divided into two continental units, Laurasia and Gondwana.

Laurasia is divided in its turn into North America and Eurasia while Gondwana separates in four continents: South America, Africa, Australia and the Antarctic. The sea Thétys also appears during this period. During this era, an intense volcanicity is responsible for the fracturing of Pangée.

Climate

From the point of view of the climate, the uniformity which reigned at the time primary education disappeared. The study of the marine fossils shows that terrestrial surface could be divided into three climatic zones, since each pole to the equator. There existed, like today, of the icy zones around the poles, characterized by a very poor fauna; zones moderated with a richer fauna, characterized especially by the abundance of the coralliaires; an equatorial zone where the life reached the maximum of intensity.

Biodiversity

Flora

The atmosphere is charged with Carbonic gas what influences much the environment. The vegetation becomes less luxuriant, which does not prevent it from presenting forms much more and higher than those of the primary time. The Cryptogame S do not have any more of so gigantic dimensions, but the Cycadée S and the Conifère S invade the drier grounds from now on. Towards the end of the secondary time, one sees appearing the Monocotylédone S and the Dicotylédone S Angiosperme S, which will take a great development during the tertiary age.

Fauna

The Mesozoic one is known under the name more familiar of age of the Dinosaure S . It is also marked by the appearance of the Oiseau X, the Mammifère S and the plants Angiosperme S.

It is characterized by a new family of Céphalopode S, that of the Ammonite S, which appears at the beginning and dies out at the end of this age.

Secondary fauna includes/understands protozoa among which the Foraminifère S perforated are very abundant; Spongiaires; Polyp S; the Crinoïde S pentacrines are very numerous; the particularly abundant Insect S in the Jurassic ; the Belemnite S, close to the cuttlefish, many too.

Higher fauna includes/understands Poisson S whose ossification is much more advanced than at the time primary education: the Téléostéens appear in the Trias.

Principal the Reptile S is the Ichthyosaure, the Plésiosaure, the nothosaure, reptiles marine; the Brontosaur, the Atlantosaure, the Iguanodon, reptiles terrestrial; the Ptérodactyle, the Ptéranodon, flying reptiles.

The Oiseau X which appear at the time secondary are initially the Archaeopteryx, the first known bird, then the Hesperornis and the Ichthyornis

Lastly, the mammals are represented by the order of the Protothériens, mammals equipped with a Marsupium.

At the end of this era, all the modern forms of life exist although, in certain cases and in particular that of the mammals, it acts of primitive forms.

Subdivisions

The Mesozoic one includes/understands the three following systems:

Sorted (between 251 and 199,6 My): development of the dinosaurs;
Jurassic (between 199,6 and 145,5 My);
Cretaceous (between 145,5 and 65,5 My): its end corresponds to the disappearance of the dinosaurs.

See too

geological time scale

External bonds

gigadino, the site on paleontology and fossils. with files and documentation
See a detailed diagram of the reptiles of the Mesozoic era

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