How long for Genus

[John Schneiderman <dino@revelation.unomaha.edu>]

A number of sources state that any species lasts for 500,000 to 1,500,000
years.  How long can a genus last before enough changes occur to consider
it a different genus.

Example: the genus Allosaurus?
Could this genus have lasted into the late Early Cretaceous? about 20
million year gap between Late Jurassic _Allosaurus fragilis_ and
Australia's Early Cretaceous _Allosaurus robustus_.
      

---John Schneiderman (dino@revelation.unomaha.edu)