Indications of the activity of living organisms
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The traces left by extinct living creatures, whether they consist of footprints, constructions or waste, are fossil elements that provide invaluable information on their ways of life, environments and past climates. A single organism, in this case a crab, can leave several types of traces indicating its presence and its activities.
- Tracks
- Burrow
- Coprolites
- Traces of food
Coprolites
Coprolites are fossilised excrement. They contain identifiable debris of animal or vegetable origin. They allow an understanding of the biological characteristics of organisms and their dietary preferences and are a particularly useful tool for examining the relations between predators and prey. They are present in many sedimentary rocks and can be very abundant in some localities. However, the animal that produced the coprolites often remains difficult to identify.
The oldest known coprolites are more that 400 million years old, originating from the first vertebrates and large invertebrates.
1. Trilobite coprolites
2. Sea cucumber coprolites
Ichnofossils
Ichnofossils are traces of the activity of organisms: footprints, burrows, furrows, nests, impressions of body parts, etc. They are of major importance for understanding past environments. Certain groups of ichnofossils, which palaeontologists call ichnofacies, are good indicators of habitat characteristics such as salinity, depth, temperature and the nature of the sediment.
Some ichnofacies, such as Cruziana, Nereites, Skolithos and Zoophycos, are marine. Others, such as Psilchnus ichnofacies, develop in marshy areas or in lake environments, for example Scoyenia ichnofacies.
3. Nereites
4. Lorenzinia
5. Scolicia
6. Spiroraphe
7. Paleodictyon
8. Cosmorhaphe
9. Asteriacites
10. Cruziana
11. Diplocraterion
12. Chondrites
13. Spirophyton
14. Rosselia
15. Planolites
16. Skolithos
Other traces
Other traces of activity of living organisms include the remains of organic structures, animal and plant parts and products. Examples are eggs, shells, carapaces, bones, teeth, leaves, spores, pollen, etc., but also traces of drilling, bites, wounds, diseases, scarring, healing, etc. All of these traces provide information on the relations between species, such as predation or even symbiosis.
17. Nassarius: Gastropod “peeled” by a crustacean.
18. Dosinia: Bivalve mollusc eroded by a gastropod.
19. Dosinia: Bivalve mollusc almost certainly pierced by a naticid.