|Holyoke Stegomastodon Tusk|
Denver Museum of Nature & Science
Relevance to my family's history is not the only reason I'm featuring Stegomastodon this month. It was among the last of the gomphotheres, one of the most prolific (though probably paraphyletic) groups of proboscideans (despite what the name might suggest, it was neither a close relative of the North American mastodon nor of the Asian Stegodon). Elephants and their relatives are one of the great triumphs of mammal evolution, due in large part to their ability to disperse widely, and Stegomastodon represents an especially important milestone in this history: it was one of only two proboscidean genera to colonize South America during the American Biotic Interchange (the other being Cuvieronius, also a gomphothere). Instead of being just an isolated specimen from eastern Colorado, then, the Holyoke Stegomastodon was part of the last great success story of a once diverse group of proboscideans, a story that unfolded not just on the Great Plains, but across Panama and into the Pampas of South America.