Science, Tech, Math › Animals & Nature Prehistoric Dog Pictures and Profiles Share Flipboard Email Print Animals & Nature Dinosaurs Prehistoric Mammals Basics Paleontologists Carnivores Dinosaurs & Birds Herbivores Marine Reptiles Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Marine Life Forestry Evolution View More By Bob Strauss Science Writer B.S., Cornell University Bob Strauss is a science writer and the author of several books, including "The Big Book of What, How and Why" and "A Field Guide to the Dinosaurs of North America." our editorial process Bob Strauss Updated April 28, 2019 01 of 13 Meet the Ancestral Dogs of the Cenozoic Era Wikimedia Commons What did dogs look like before Gray Wolves were domesticated into modern poodles, schnauzers and golden retrievers? On the following slides, you'll find pictures and detailed profiles of a dozen prehistoric dogs of the Cenozoic Era, ranging from Aelurodon to Tomarctus. 02 of 13 Aelurodon National Museum of Natural History Name: Aelurodon (Greek for "cat tooth"); pronounced ay-LORE-oh-don Habitat: Plains of North America Historical Epoch: Middle-late Miocene (16-9 million years ago) Size and Weight: About five feet long and 50-75 pounds Diet: Meat Distinguishing Characteristics: Dog-like build; strong jaws and teeth For a prehistoric dog, Aelurodon (Greek for "cat tooth") has been given a somewhat bizarre name. This "bone-crushing" canid was an immediate descendant of Tomarctus, and was one of a number of hyena-like proto-dogs that roamed North America during the Miocene epoch. There's evidence that the larger species of Aelurodon may have hunted (or roamed) the grassy plains in packs, either taking down diseased or aged prey or swarming around already-dead carcasses and cracking the bones with their powerful jaws and teeth. 03 of 13 Amphicyon Sergio Perez True to its nickname, Amphicyon, the "bear dog," looked like a small bear with the head of a dog, and it probably pursued a bear-like lifestyle as well, feeding opportunistically on meat, carrion, fish, fruit and plants. However, it was more ancestral to dogs than to bears! 04 of 13 Borophagus Wikimedia Commons Name: Borophagus (Greek for "voracious eater"); pronounced BORE-oh-FAY-gus Habitat: Plains of North America Historical Epoch: Miocene-Pleistocene (12-2 million years ago) Size and Weight: About five feet long and 100 pounds Diet: Meat Distinguishing Characteristics: Wolf-like body; large head with powerful jaws Borophagus was the last of a large, populous group of North American predatory mammals informally known as the "hyena dogs." Closely related to the slightly bigger Epicyon, this prehistoric dog (or "canid," as it should technically be called) made its living much like a modern hyena, scavenging already-dead carcasses rather than hunting live prey. Borophagus possessed an unusually big, muscular head with powerful jaws, and was probably the most accomplished bone-crusher of its canid line; its extinction two million years ago remains a bit of a mystery. (By the way, the prehistoric dog formerly known as Osteoborus has now been assigned as a species of Borophagus.) 05 of 13 Cynodictis Wikimedia Commons Until recently, it was widely believed that the late Eocene Cynodictis ("in-between dog) was the first true "canid," and thus lay at the root of 30 million years of dog evolution. Today, though, its relationship to modern dogs is subject to debate. 06 of 13 The Dire Wolf Daniel Anton One of the apex predators of Pleistocene North America, the Dire Wolf competed for prey with the Saber-Toothed Tiger, as evidenced by the fact that thousands of specimens of these predators have been dredged up from the La Brea Tar Pits in Los Angeles. 07 of 13 Dusicyon Wikimedia Commons Not only was Dusicyon the only prehistoric dog to live on the Falkland Islands (off the coast of Argentina), but it was the only mammal, period – meaning it preyed not on cats, rats and pigs, but birds, insects, and possibly even shellfish that washed up along the shore. 08 of 13 Epicyon Wikimedia Commons The largest species of Epicyon weighed in the neighborhood of 200 to 300 pounds – as much as, or more than, a full-grown human – and possessed unusually powerful jaws and teeth, which made their heads look more like those of a big cat than a dog or wolf. 09 of 13 Eucyon Wikimedia Commons Name: Eucyon (Greek for "original dog"); pronounced YOU-sigh-on Habitat: Plains of North America Historical Epoch: Late Miocene (10-5 million years ago) Size and Weight: About three feet long and 25 pounds Diet: Meat Distinguishing Characteristics: Medium size; enlarged sinuses in snout To simplify matters just a bit, the late Miocene Eucyon was the last link in the chain of prehistoric dog evolution before the appearance of Canis, the single genus that encompasses all modern dogs and wolves. The three-foot-long Eucyon was itself descended from an earlier, smaller genus of dog ancestor, Leptocyon, and it was distinguished by the size of its frontal sinuses, an adaptation linked to its diverse diet. It's believed that the first species of Canis evolved from a species of Eucyon in late Miocene North America, about 5 or 6 million years ago, though Eucyon itself persisted for another few million years. 10 of 13 Hesperocyon Wikimedia Commons Name: Hesperocyon (Greek for "western dog"); pronounced hess-per-OH-sie-on Habitat: Plains of North America Historical Epoch: Late Eocene (40-34 million years ago) Size and Weight: About three feet long and 10-20 pounds Diet: Meat Distinguishing Characteristics: Long, sleek body; short legs; dog-like ears Dogs were only domesticated about 10,000 years ago, but their evolutionary history goes back way further than that--as witness one of the earliest canines yet discovered, Hesperocyon, which lived in North America a whopping 40 million years ago, during the late Eocene epoch. As you might expect in such a distant ancestor, Hesperocyon didn't look much like any dog breed alive today, and was more reminiscent of a giant mongoose or weasel. However, this prehistoric dog did have the beginnings of specialized, dog-like, meat-shearing teeth, as well as noticeably dog-like ears. There's some speculation that Hesperocyon (and other late Eocene dogs) may have led a meerkat-like existence in underground burrows, but the evidence for this is somewhat lacking. 11 of 13 Ictitherium American Museum of Natural History Name: Ictitherium (Greek for "marten mammal"); pronounced ICK-tih-THEE-ree-um Habitat: Plains of northern Africa and Eurasia Historical Epoch: Middle Miocene-Early Pliocene (13-5 million years ago) Size and Weight: About four feet long and 25-50 pounds Diet: Omnivorous Distinguishing Characteristics: Jackal-like body; pointed snout For all intents and purposes, Ictitherium marks the time when the first hyena-like carnivores ventured down from the trees and skittered across the vast plains of Africa and Eurasia (most of these early hunters lived in North America, but Ictitherium was a major exception). To judge by its teeth, the coyote-sized Ictitherium pursued an omnivorous diet (possibly including insects as well as small mammals and lizards), and the discovery of multiple remains jumbled together is a tantalizing hint that this predator may have hunted in packs. (By the way, Ictitherium wasn't technically a prehistoric dog, but more of a distant cousin.) 12 of 13 Leptocyon Wikimedia Commons Name: Leptocyon (Greek for "slender dog"); pronounced LEP-toe-SIGH-on Habitat: Woodlands of North America Historical Epoch: Oligocene-Miocene (34-10 million years ago)) Size and Weight: About two feet long and five pounds Diet: Small animals and insects Distinguishing Characteristics: Small size; fox-like appearance Among the earliest ancestors of modern dogs, various species of Leptocyon roamed the plains and woodlands of North America for a whopping 25 million years, making this small, foxlike animal one of the most successful mammalian genera of all time. Unlike larger, "bone-crushing" canid cousins like Epicyon and Borophagus, Leptocyon subsisted on small, skittering, live prey, probably including lizards, birds, insects and other small mammals (and one can imagine that the larger, hyena-like prehistoric dogs of the Miocene epoch themselves weren't averse to making an occasional snack out of Leptocyon!) 13 of 13 Tomarctus Wikimedia Commons Name: Tomarctus (Greek for "cut bear"); pronounced tah-MARK-tuss Habitat: Plains of North America Historical Epoch: Middle Miocene (15 million years ago) Size and Weight: About four feet long and 30-40 pounds Diet: Meat Distinguishing Characteristics: Hyena-like appearance; powerful jaws Like another carnivore of the Cenozoic Era, Cynodictis, Tomarctus has long been the "go-to" mammal for folks who want to identify the first true prehistoric dog. Unfortunately, recent analysis has shown that Tomarctus wasn't any more ancestral to modern dogs (at least in a direct sense) than any of the other hyena-like mammals of the Eocene and Miocene epochs. We do know that this early "canid," which occupied a place on the evolutionary line that culminated in apex predators like Borophagus and Aelurodon, possessed powerful, bone-crushing jaws, and that it wasn't the only "hyena dog" of middle Miocene North America, but other than that much about Tomarctus remains a mystery.