In Depth
Not to be confused with the bear dogs which were dog-like mammals that resembled bears; Hemicyon was what is loosely termed a dog bear, which is a bear that is more dog-like. In simple terms, Hemicyon was more closely related to bears than dogs. Hemicyon had a very important difference between it and other ancestors of the bears and this is that it was digitigrade. This means that Hemicyon walked on its toes with the foot bones serving to extend the length of the leg. Bears today by contrast are plantigrade which means that the full foot is always in contact with the ground as they walk.
The advantage of being digitgrade is that with the leg effectively being longer it can cover more ground with each stride, something that suggests that Hemicyon would have been a proportionately faster animal than other primitive bear forms. This speed may have helped it to chase down primitive horses like Merychippus and Hipparion, which were reasonably fast herbivores that had become adapted to the plains environments that were spreading across most of the major continents during the Miocene.
With a broad distribution that covered most of the northern hemisphere and a temporal range that covers most of the Miocene period, Hemicyon was undoubtedly a successful genus, but also one that was inevitably doomed to extinction. Just as the bear dogs and dog bears replaced creodonts like Hyaenodon as the dominant predators, they themselves would have been replaced by the more advanced and quite possibly more intelligent ancestors of true dogs as well as big cats that together would have specialised to fill all predatory niches in Cenozoic ecosystems.
Further Reading
– The Hemicyoninae and an American Tertiary bear. – Bulletin of the American Museum of Natural History 56(1):1-119. – C. Frick – 1926.- The Ancestral Ursid, Hemicyon, in Nebraska. – Bulletin of the Nebraska State Museum 2(5):49-57. – E. H. Colbert – 1941.- Hemicyon mayorali nov. sp., an Ursidae from the Middle Miocene of Tarazona de Aragon (Ebre basin, Spain). – Annales de Paleontologie, Volume 86, Number 1. – H. Astibia, J. Morales & L. Ginsburg – 2000.
