About 7-11 MYA, the Ursinae (possibly Ursavus or Protursus) split (O'Brien et al. 1985).  The main branch became genus Ursus, including at least 2 extinct subgenera (European cave bears and ancestral black bears) and 6 living ones: modern Eusian black bears (subgenus Selenarctos), American black bear (subgenus Euarctos), brown/grizzly (subgenus Ursus), polar bear (subgenus Thalarctos), sun bear (subgenus Helarctos) and sloth bears (subgenus Melursus).  Sun and sloth bears apparently diverged from from the ancestral Ursus stock before other species did.  
 
 
 
 
 
 
                                     Ch. 4b:  Etruscan & Cave Bears  
                                     Ch. 4c:  Modern Grizzly/Brown, Polar, Sun & Sloth Bears
 
Chapter 4.  URSINAE
Chapter 4.  URSINAE (cont.) >>