Wikipedia
Paleoendemism along with neoendemism is one of two sub-categories of endemism. Paleoendemism refers to species that were formerly widespread but are now restricted to a smaller area. Neoendemism refers to species that have recently arisen, such as through divergence and reproductive isolation or through hybridization and polyploidy in plants.
It is not always clear whether a particular species is paleoendemic or neoendemic. For example, kiwis, which are confined to New Zealand, were cited as examples of paleoendemism because most parts of the former supercontinent Gondwana have ratites, or did have until the fairly recent past. The traditional account of ratite evolution has the group emerging in flightless form in Gondwana in the Cretaceous, then evolving in their separate directions as the continents drifted apart. More recently, “overwater dispersal” has been hypothesised for the arrival of kiwis in New Zealand.