Chronospecies

A chronospecies is a species derived from a sequential development pattern that involves continual and uniform changes from an extinct ancestral form on an evolutionary scale.

That identification relies on distinct similarities between the earlier fossil specimens and some proposed descendant although the exact relationship to the later species is not always defined.

The further identification of fossil specimens as part of a "chronospecies" relies on additional similarities that more strongly indicate a specific relationship with a known species.

For example,[1] relatively recent specimens, hundreds of thousands to a few million years old with consistent variations (such as always smaller but with the same proportions) as a living species might represent the final step in a chronospecies.

The concept of chronospecies is related to the phyletic gradualism model of evolution, and it also relies on an extensive fossil record since morphological changes accumulate over time, and two very different organisms could be connected by a series of intermediaries.

In palaeontology , the evidence for species and evolution comes mainly from the comparative anatomy of fossils . A chronospecies is defined in a single lineage (solid line) whose morphology changes with time. At some point, palaeontologists judge that enough change has occurred that two forms (A and B), separated in time and anatomy, once existed. If only sporadic examples of each survive in the fossil record, the forms will appear sharply distinct.