Whenever the word Fossil comes to our mind we suddenly think about dinosaurs and their fossils because, since our childhood we have mostly learned about dinosaurs, so, since then we all have a mind setup about dinosaurs but have you ever asked yourself, Did fossils came in existence after dinosaurs or do they exist before them(Dinosaurs). So, here are the answers of all your questions, in this article, you will know about the history of paleontology from where they came, Facts of Fossils, some may be unbelievable and some of them you might you not be knowing you will also get to know about the Types of fossils. So let’s explore our knowledge more about fossils and dinosaurs.
History of Paleontology/Fossils
Fossils and the history of life – Summary
Fossils are formed when the remains of an organism are preserved in the sediment deposited at the bottom of the water column; the sediment may then form a sedimentary rock by compaction over time. If that sedimentary rock is later exposed at the surface of the earth, the fossils can be removed from it.
The history of the earth is divided into a series of timed stages. Most fossils are from organisms that lived in the past 600 million years. The 600 million year period is divided into three Eras (Paleozoic, Mesozoic, Cenozoic); the Eras, in turn, are divided into successively into Periods and Epochs.
Fossil during the Paleozoic age
Rock during the Mesozoic era
Hunting of a mammoth during the ice age(Cenozoic era)
Rock ages can be measured absolutely using their radio-isotopic composition, and relatively by correlating their fossil content with other rocks elsewhere. Magnetic time zones also provide useful chronological evidence.
The fossil record provides evidence of the history of life:
Life originated over 3.5 billion years ago.
- Prokaryotic cells already existed 3.5 billion years ago.
- Eukaryotic cells originated maybe 1.8 billion years ago.
- Photosynthesis expanded at a similar time and caused an increase in the oxygen concentration of the Earth’s atmosphere.
- Multicellular life appears first, in soft-bodied animals, in the Ediacarian faunas of 670 – 550 million years ago.
- Hard-bodied animals evolved about 550 million years ago and their appearance led to a much richer fossil record, starting with the Cambrian.
- Terrestrial ecosystems were colonized from the Ordovician onward, and the fossil record provides good evidence concerning the evolution of reptiles, and the origin of birds and of mammals from reptilian ancestors.
The completeness of the fossil record can be studied, at a gross level, by the geological continuity of the rock sequence; and at a finer level by estimating the percentage of the total time range represented by the rocks during which sediments were actually being deposited.
The evolution of mammals from reptiles is an example of adaptive evolution and the fossil record reveals that it proceeded in a series of stages, through various groups of mammal-like reptiles.
Formation of fossils
Body Fossils and Trace Fossils
Body fossils are the remains of the body parts of ancient animals, plants, and other life forms. They tell us something about the appearance of ancient life forms.
Body fossil example 1
A fossilized leaf from the Eocene-aged Green River Formation (preserved as a carbonization). Because of the excellent quality of preservation, little imagination is required to reconstruct the appearance of the once-living leaf. This specimen is on display at the Utah Field House of Natural History in Vernal, Utah.
Body fossil example 2
An assemblage of well-preserved fossil Turritella snail shells from the Miocene-aged Gatun Formation of Panama, showing unaltered preservation, despite being over 10 million years old.
Trace fossils (sometimes also called ichnofossils) provide evidence about the movements and/or activities of ancient organisms, but not necessarily about their appearance. There are three major types:
- Movement traces.
- Predation traces.
- Digestive traces.
1. Movement traces
As their name implies, movement trace fossils tell us about how ancient animals moved within their habitats. It is easy to grasp why such fossils are so useful for understanding ancient life.
Consider the footprints you might leave behind as you walk on a sandy beach or through the snow. While they don’t reveal much about your appearance (besides the general size and shape of the bottom of your foot or shoe), they reveal the direction you were moving, whether you were traveling alone or in a group, and also provide clues about whether you were walking (footprints close together) or running (footprints further apart).
Dinosaur footprints provide the best examples of movement trace fossils and provide paleontologists with the same kinds of clues that human footprints do.
Discoveries of dinosaur footprints and trackways–left behind in soft sediment that later turned to rock–are not altogether rare and new discoveries are made regularly. For example, a massive footprint left behind by a titanosaur was recently discovered in the Gobi Desert.
Not all movement trace fossils are footprints, however. Other types of movement traces include the trails and burrows left behind by animals in the sediment before it hardened. Sediments that were heavily mixed by burrowing organisms prior to turning to rock are said to be bioturbated. Such bioturbated rocks usually lack finely preserved layers; the absence of such layers is sometimes an indication for geologists that the sediments were well oxygenated, thus allowing animals to crawl through them.