1- Body fossils: are fossils that represent remains of the actual organism or its skeleton. They occur in many ways, including: unaltered preservation, recrystallization, replacement, permineralization, carbonization, impressions, casts and molds.
2- Trace fossils: Unlike body fossils, where a portion of the actual organism or its skeleton is preserved, trace fossils are the remains of an organism's activity or behavior. Examples include tracks, trails, burrows, and borings.
3- Pseudofossils: unusual structures formed inorganically that, by chance, resemble body or trace fossils. examples dendrites. These are inorganic precipitates of manganese oxide that were described originally as fossil algae.
Fossils in general may have long range and these are called Range fossils, these fossils can’t be used as time indicators. Other fossils are characterized by wide geographic distribution and short range; these are called Index (guide) fossils and are useful in designating the age of strata.
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