The Bulletin of the American Museum of Natural History has a massive, and I do mean massive, paper on the Brontotheriidae freely available for download. Species taxonomy, phylogeny and biogeography of the Brontotheriidae (Mammalia, Perissodactyla) They also have another interesting paper called Phylogeny and systematics of Squamata (Reptilia) based on morphology also freely available.
Update 1: Here is a bit from the abstract that I found interesting:
Nine to twelve intercontinental dispersals, mostly in the middle Eocene (Uintan and Irdinmanhan land mammal ”ages”) between North America and Asia are implied by the
cladistic results. The timing of these dispersals agrees with prior conclusions regarding the timing of large influxes of mammal taxa into North America from Asia. However, the frequency of
interchanges is far greater than previously surmised. Following basic MacArthur-Wilson island
biogeography theory, North America, the smaller continent, is viewed as a cul-de-sac, receiving
repeated waves of immigrants from Asia, the larger continent. However, the phylogenetic results
of the Brontotheriidae suggest the possibility that the predominant direction of dispersal could
have been in the opposite direction; this result questions the validity of applying island
biogeography theory to continent-scale dispersal dynamics.
That was the conclusion of the recent article on mammoths as well.
Filed under: Paleontology | Tagged: Brontotheriidae |
Afarensis: Anthropology, Evolution, and Science 
Sweet! A revision of the brontotheres has been a long time coming. Now we just need someone to take care of the Dinocerata…
The idea of species consistently moving from larger to smaller continents has always been considerably shaken by horse and camel evolution. I believe it’s generally accepted these two groups had their main origin and dispersal from North America. And there’s quite a bit of evidence that many bird species originating in the Pacific islands have moved back to New Guinea and mainland Asia.