Some authors include pseudoextinctions amongst extinctions (Fig. XXII.1). This term is used to designate the disappearance of a certain species from the paleontological record as a consequence of its gradual transformation into another species. The average phenotype of the members of a certain species gradually changed over time so that, after a certain time, it differed from the original phenotype to such a degree that paleotaxonomists begin to consider it to be a separate new species. Species delimited in this way are sometimes termed chronospecies. Basically, during pseudoextinction, the original species did not actually die out in the true sense of the word, but was only transformed into new species. In most taxa, true pseudoextinction is a rather rare phenomenon (see the sections concerned with punctuated evolution). Nonetheless, its existence must be taken into account. A considerable number of pseudoextinctions reflect the tendency of paleontologists to call a single species occurring in subsequent paleontological zones by different names. Completely different laws govern pseudoextinction than those of real extinctions and it will not be further considered in this chapter. See alo Speciation branching

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more