A chronospecies is a species which changes physically, morphologically, genetically, and/or behaviorally over time on an evolutionary scale such that the originating species and the species it becomes could not be classified as the same species had they existed at the same point in time. Throughout this change, there is only one species in the family line living at any point in time, as opposed to cases where one species branches off into many through divergent evolution.

With a phyletic gradualism model of evolution, it can be difficult to separate chronospecies, since morphological changes accumulate over time and two very different organisms could be connected by a series of intermediaries. In practice, chronospecies are usually recognized because two species in the same lineage are named by palaeontologists without knowledge of any intermediate organisms. When organisms evolve by punctuated equilibrium, chronospecies can be readily seen in the fossil record when a lineage changes without splitting.

References

• Stanley, S. M. (1978) "Chronospecies' longevities, the origin of genera, and the punctuational model of evolution," Paleobiology, 4, 26-40.
• Evolutionary species vs. chronospecies from Dr. Steven M. Carr, Memorial University of Newfoundland biology department

Chronospezies