Quote of the day--of immigration, from dire wolf wiki

The three noted paleontologists Xiaoming Wang, Richard H. Tedford and R. M. Nowak proposed that C. dirus evolved from the large wolf Canis armbrusteri^{[21]:181[20]:p52} (Armbruster's wolf),^[22] with Nowak stating that there were specimens from Cumberland Cave, Maryland that indicate C. armbrusteri diverging into C. dirus.^{[23][24]:p243} The early wolf from China, Canis chihliensis, may have been the ancestor of both C. armbrusteri and the gray wolf C. lupus.^[21]:146 The sudden appearance of C. armbrusteri in North America during the Early Pleistocene suggests that this was an immigrant from Asia, 

Accessed 2-10-2017