Discussion
Right then...
As of right now there are countless lifeforms of various types on earth and when they die there will be no trace of them, so we will never know they existed.
So I was watching the telly the other night and there was prehistoric foot and tail prints in some rock of some big old reptile. How come it managed to leave some foot prints in some mud and the mud hardened to such an extent that they got preserved for millennia?
As of right now there are countless lifeforms of various types on earth and when they die there will be no trace of them, so we will never know they existed.
So I was watching the telly the other night and there was prehistoric foot and tail prints in some rock of some big old reptile. How come it managed to leave some foot prints in some mud and the mud hardened to such an extent that they got preserved for millennia?
Millions and millions of animals leaving prints in millions of acres of mud over 10s of millions of years. Chances are that at some point the mud will dry / flood / laminate and harden. The edge of wet areas would be good for finding water and food, so it is natural that animals would congregate there, if only to predate on each other.
"Trace Fossils", as animal tracks or footprints are known, are some of the most common forms of fossils. They are very useful to paleontologists as they are, unlike a normal fossil, an indicator of an animal that was still alive when it made them. The problem is that it isn't always possible to determine the actual type of animal that actually left the footprint or track.
On rare occasions, the remains of the animal may be found near the track it left.
All sorts of animal tracks have been found, from burrowing worm tubes to footprints left be giant sauropud herds. Even human footprints have been left fossilised, There is a lovely set of footprints left on a fossilised beach near Liverpool.
On rare occasions, the remains of the animal may be found near the track it left.
All sorts of animal tracks have been found, from burrowing worm tubes to footprints left be giant sauropud herds. Even human footprints have been left fossilised, There is a lovely set of footprints left on a fossilised beach near Liverpool.
As MartG states, the imprint has to be infilled with another material in order for it to be preserved, this mold and cast combination then has to be turned to stone (Lithified). This normally occurs due to the sediment being buried by hundreds of meters of other sediment and a cement being deposited around the individual grains of sand or silt for warm water which permeates the sediment (Diagenesis). The rock then has to be uplifted back to the surface (Techtonics) and then the rocks on top have to be removed in order for the fossil to be revealed (Erosion).
Normal fossils (i.e. shells, bones) are not the actual animals hard parts, they are replaced during Diagenesis. And this has to happen, if you find an actual Dinosaur bone then your not looking at a fossil your looking at a bone and you would be about to become incredibly rich! Therefore in the case of the trace fossil you are looking at either the cast or the mold (or both if you are lucky!) not the actual foot print.
Foot prints of land animals are really rare. The environments in which you would leave a foot print are highly changeable, i.e. mud on river bank -> water rises when it rains -> destroys foot prints. One thing you can be sure of when looking at a fossil was that the animal that it represents was really really common, doubly so for a land animal and double again for a trace fossil of a land animal. Fossils of land animals that live away from the coast/lakes or rivers, i.e. on the side of a mountain or in semi arid environments are unheard of in the fossil record they just don't get the opportunity to get preserved.
How do we know dinosaurs were common? because we found one fossil. How do we know they rule the Earths land? Because we found more than one.
Normal fossils (i.e. shells, bones) are not the actual animals hard parts, they are replaced during Diagenesis. And this has to happen, if you find an actual Dinosaur bone then your not looking at a fossil your looking at a bone and you would be about to become incredibly rich! Therefore in the case of the trace fossil you are looking at either the cast or the mold (or both if you are lucky!) not the actual foot print.
Foot prints of land animals are really rare. The environments in which you would leave a foot print are highly changeable, i.e. mud on river bank -> water rises when it rains -> destroys foot prints. One thing you can be sure of when looking at a fossil was that the animal that it represents was really really common, doubly so for a land animal and double again for a trace fossil of a land animal. Fossils of land animals that live away from the coast/lakes or rivers, i.e. on the side of a mountain or in semi arid environments are unheard of in the fossil record they just don't get the opportunity to get preserved.
How do we know dinosaurs were common? because we found one fossil. How do we know they rule the Earths land? Because we found more than one.
Simpo Two said:
There are a lot of rabbits, but they don't rule the earth.
But imagine they were two metres tall and carnivorous. OP, as has been said, chance. The right circumstances and voila. It's why there are some areas where fossils are rich. It's not necessarily because lots of stuff died right there, just that lots of stuff was preserved.
Willy and others above refer to fossil footprints from millions of years ago, but the process continues. In the Severn Estuary, certain mudbanks are being eroded by the river, and every tide reveals footprints and tracks of people and animals who were there 'only' thousands of years ago. These will never fossilise into rock, but if geography and geology had been different, and if the mud had been covered by more sediment and over aeons turned into rock, they would look similar to the dinosaur prints.
See: http://www.bbc.co.uk/news/uk-wales-south-east-wale...
John
See: http://www.bbc.co.uk/news/uk-wales-south-east-wale...
John
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