I am no expert on mammals, but do know a bit about plant fossils, and in
the case of the angiosperms and in fact most plants, the fossil record is
much different from that of mammals. In fact, angiosperms are from their
first appearance generally attributable to extant genera, and this is true
for many other plant forms as well. (Maybe that is because plants don't
have dentition!). This is a very different picture from that presented by
animals in general, although there are a few animal genera that are long
ranging such as Lingula. As far as species go, there are ~600 endemic
species of Drosophila in the Hawaiian Islands. No matter what one believes
to be the origin of the Fossil Record, species arenot the issue.
Art
http://chadwicka.swau.edu