Cockroach dating fossil history million

Although it is common to say that living fossils exhibit "morphological stasis", stasis, in the scientific literature, does not mean that any species is strictly identical to its ancestor, much less remote ancestors.

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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.Early analyses of evolutionary rates emphasized the persistence of a taxon rather than rates of evolutionary change.Contemporary studies instead analyze rates and modes of phenotypic evolution, but most have focused on clades that are thought to be adaptive radiations rather than on those thought to be living fossils.A dramatic example was the order Coelacanthiformes, of which the genus, Latimeria was found to be extant in 1938. However, whether Latimeria resembles early members of its lineage sufficiently closely to be considered a living fossil as well as a Lazarus taxon, has been denied by some authors in recent years.Coelacanths disappeared from the fossil record some 80 million years ago (upper Cretaceous) and to the extent that they exhibit low rates of morphological evolution, extant species qualify as living fossils.

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