A chronospecies is a species which changes physically, morphologically, genetically, and/or behaviorally over time on an evolutionary scale (experiences a phyletic shift) such that the species from the early point in time and the species it becomes at the later point in time could not be classified as the same species had they existed at the same point in time. Throughout the change, there is only one species at any point in time and diversity does not increase.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.