Fossil dating wiki

One example of a concept that could be confused with "living fossil", is that of a "Lazarus taxon", but the two are not equivalent; a Lazarus taxon (whether a single species or a group of related species) is one that suddenly reappears, either in the fossil record or in nature, as if the fossil had "come to life again".

In contrast to Lazarus taxa, a living fossil in most senses is a species or lineage that has undergone exceptionally little change throughout a long fossil record, giving the impression that the extant taxon had remained identical through the entire fossil and modern period.

Lineages that exhibit stasis over very short time scales are not considered living fossils; what is poorly-defined is the time scale over which the morphology must persist for that lineage to be recognized as a living fossil.A living fossil is an extant taxon that closely resembles organisms otherwise known only from the fossil record.As a rule, to be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade.To determine much about its noncoding DNA is hardly ever possible, but even if a species were hypothetically unchanged in its physiology, it is to be expected from the very nature of the reproductive processes, that its non-functional genomic changes would continue at more or less standard rates.It follows that a fossil lineage with apparently constant morphology need not imply equally constant physiology for example, and certainly neither implies any cessation of the basic evolutionary processes such as natural selection, nor reduction in the usual rate of change of the noncoding DNA.

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