The subfamily Borophaginae is an extinct group of canids called "bone crushing dogs" that were endemic to North America during the Oligocene to Pliocene and lived roughly 36—2.5 million years ago and existing for approximately . Origin The Borophaginae apparently descended from the subfamily Hesperocyoninae; they evolved to become considerably larger than their predecessors, and filled a wide range of niches in late Cenozoic North America, from small omnivores to powerful, bear-sized carn… (More on Borophaginae)