A paleosubspecies (or palaeosubspecies) identifies an extinct subspecies which evolved into the currently existing form. This connection with relatively recent variations, usually from the Late Pleistocene, often relies on the additional information available in subfossil material. Most of the current species have changed in size adapting to the climatic changes during the last ice age (see Bergmann's Rule).
The further identification of fossil specimens as part of a "chronospecies" relies on additional similarities which more strongly indicate a specific relationship with a known species. For example, relatively recent specimens – hundreds of thousands to a few million years old – with consistent variations (e.g. always smaller but with the same proportions) as a living species might represent the final step in a chronospecies. This possible identification of the immediate ancestor of the living taxon may also rely on stratigraphic information to establish the age of the specimens.
The concept of chronospecies is related to the phyletic gradualism model of evolution, and 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.