When the conversation turns to apex predators it will not be long before the African lion, the Bengal tiger, the polar bear, the saltwater crocodile, the great white shark and the orca have each shared their moment in the limelight. Next, someone is sure to draw attention to the great extinct killers of the relatively recent past, geologically speaking. The saber toothed cat is bound to put in an appearance, along with the short faced bear, the American lion and perhaps the dire wolf.
Rolling back the clock Tyrannosaurus rex is bound to raise his formidable head, accompanied by Giganotosaurus, Spinosaurus, Megalodon and the grand daddy of all crocodilians, Sarcosuchus imperator. The list goes on and on, but rarely will it include even a single creodont, a widely distributed order of predatory mammals which enjoyed a run of nearly fifty million years, an order which included some of the most formidable and terrifying creatures ever to walk the earth and yet one which is virtually unknown to the general public.
The first creodonts emerged in the early Paleocene, only one of the “new” orders filling the immense hole in the biosphere left by the terrible K/T extinction that killed off the dinosaurs and much other life only a few million years earlier. First to appear were the Oxyaenidae, a family that would become extremely successful and included mostly cat like and bear like meat eaters. Typical of the early species was oxyaena, a smallish – 6 to 18 lb – low slung animal, cat like both in appearance and habit, preying on birds and their eggs, small vertebrates and the occasional insect.
Last to leave, as far as we know from the evidence available was Dissopsalis carnifex from the second major creodont genus, the hyaenodonta. Dissopsalis survived into the late Miocene vanishing about 9 million years ago, the last species to have endured for so long, and that by a margin of millions of years.
Dissopsalis was a mid sized, generally wolf shaped animal with the plantigrade – flat footed - mode of locomotion typical of its order, much like the modern raccoon and the recently extinct Thylacine.
If the Paleocene heralded the arrival of the Creodonts, and the Miocene their demise, the Eocene and Oligocene were their heydays, a time of dominance as far as warm blooded predation is concerned. The Eocene, for example brought forth Sarkastodon mongoliensus, a titanic bear like predator and legitimate contender for the crown of all time largest warm blooded meat eater. Other contenders include the short faced bear, Andrewsarchus mongoliensus and fellow enigmatic Creodont, Megistotherium.
Fossil remains of Sarkastodon are few and most are known from Eocene formations in Mongolia. These reveal a robust bear shaped animal, standing perhaps a yard and a half tall at the shoulder with a body perhaps 12 feet in length, equipped with a large raccoon like tail. The jaws were extremely powerful, capable of shearing and bone crushing. The animal could reach nearly 19 feet in the air when standing on its hind legs and reaching up. Weight estimates run as high as three thousand pounds but this would have been at the upper range of probability.
Prey would have included Chalicotheres, early Rhinocerenes and Brontotheres. As with most large meat eaters, Sarkastodon was very likely to be an opportunistic scavenger as well as a hunter.
Less is known about Megistotherium osteothlastes but it must have been a formidable creature indeed. The name, which means “largest bone crushing beast” gives some idea of its potential. Slightly taller at the shoulder than Sarkastodon and a bit longer as well, Megistotherium roamed what are now the Saharan desert countries in the late Oligocene and early Miocene. Megistotherium was from the wolf like, hyaenodonta family of Creodonts and shared the superficial wolf like characteristics of that order.
A close relative of Megistotherium, Hyaenodon gigas, was only slightly smaller than Megistotherium. This animal was featured in the ABC television special, “Walking with Beasts”.
Both Megistotherium and Sarkastodon, mighty as they undoubtedly were found themselves gradually forced from the evolutionary stage under pressure from the modern carnivores. This may have been in part due to their relatively smaller brain size as determined by a comparison of brain case castings made using the skulls of both orders. It may too be a result of a somewhat less agile body design, Creodonts lacked digitagrade locomotion, instead running with the less efficient flat footed plantigrade style, and also lacked flexibility of the leg and wrist joints. This denied them a big cats ability to grasp and kill with its’ claws.
But bear, dog and cat like predators did not make up the entire spectrum of Creodont development. There was also Macheroides, a saber toothed creodont that science is having a hard time placing in either of the Hyaenidae or Oxyaenidae families and which may possibly constitute a family of its’ own. These enigmatic predators were certainly less terrifying than some of their larger cousins. Macheroides rarely exceeded 25 pounds in weight.
Unlike Smilodon and the Dire wolf, the Creodonts were long gone before man came on the scene. But this does not mean that there were no more or less close encounters of the deadly kind. University of Minnesota researcher Kirsten Jenkins, working on the Kenyan island of Rusinga has discovered numerous fossils of the hominoid primate, Proconsul Africanus. Many of these fossils show extensive bite and crush marks from the unique dentition of a creodont very much like if not identical too, Hyaenodon horridus.
Granted, these predations took place some 20 million years ago and the primates involved were far removed, perhaps not even in a direct line to Homo sapiens. Never the less, when talk turns to deadly predators these fascinating creatures, extant for nearly 50 million years and dominant for 35 million of those, an order that produced at least 180 distinct species that we know of and which included the largest warm blooded killing machines the earth has ever seen deserve at least passing mention.