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Guide Fossil: Estromatolitos
Geologic event: Origin and early evolution of the earth
Climate event: First glaciations -
Appearance of the first life forms with microscopic size. They lived only in water and there was no life outside of it. Cyanobacteria (photosynthetic bacteria) appeared and then the first multicellular life forms. Que tipo de formas de vida
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They have eukaryotic cells (cells with nuclei), were invertebrates and were multicellular life forms. The main multi-cellular life forms were the stromatolites. -
This explosion of life gave way to a new era called "Paleozoic" and was caused by several reasons: The important climatic changes such as glaciations or low sea levels...
(The image was be one of the first animals that appeared) -
Guide Fossil: Triboleites
Geologic event: Pangea formation
Climate event: More glaciations and low sea levels -
Fish developed, being the dominant fish of this era (Paleozoic). In the oceans, primitive sharks become more numerous and the first lobe-finned fish and bony fish appear. -
There is a warm and humid climate that helps to advance the development of the great extensions of coastal marshlands and the irruption of the great forests of conifers and ferns.
It is found in the Paleozoic era (Carboniferous). -
Some of the features that allowed amphibians to emerge from the water were:
- Evolution of the lungs
- Development of the choanae
- Appearance of a limb (the legs).
Ichthyostegids were the first amphibians that were able to leave the water. -
Guide Fossil: Amonites
Geologic event: Pangea fragments
Climate event: Dry and hot climate. No glaciation -
Large reptiles colonise all environments, both terrestrial and aquatic. These reptiles are the main guiding fossils of this era. Approximately 70 million years later, these dominants of the earth became extinct and new colonisers appeared. -
Plants undergo great diversification, especially conifers and angiosperms, which, unlike gymnosperms, have flowers and fruit. They first appeared about 125 m.y. ago and diversified rapidly about 100 m.y. ago. Deciduous angiosperms came to predominate in colder regions, while evergreen varieties prevailed in the subtropics and tropics. -
Guide Fossil: Nummulites
Geologic event: Formation of ice caps and development of the Alpine Orogeny
Climate event: 4 glaciations alternating with warm periods -
The first birds appeared 201 m.b.y. ago but diversified 23 m.y. ago. They developed from therapsids, a group of carnivorous dinosaurs. (In the picture you can see a huge bird of this era called Gastornis.) -
They were primates adapted to life on land, walking upright in a bipedal posture. The term "hominid" refers to any being, present or past, that has been part of the human race.
One of the first primates were the Sahelanthropus tchadensis or Orrorin tugenensis. -
The Quaternary begins with the appearance of Homo sapiens 2m.y. ago. Their oldest remains are 195,000 years old and were found in Ethiopia. The first homosapiens, in terms of physical characteristics, resemble today's people.