Nimravids

Close, But No Cigar!

Nimravids look like cats, but aren't! About 50 million years ago, the nimravids and true cats diverged from a common ancestor. Due to parallel development, nimravids are remarkably similar to cats - particularly the sabertooth cats.
     Like the sabertooth cats, nimravids came in a variety of sizes and had huge saber-teeth. Some nimravids did evolve into large toothed cat-like forms with massive flattened upper canines and accompanying mandibular flanges. The flanges act like sheathes for the long canine teeth. Others had dentition similar to modern felids with smaller canines. Others had moderately increased canines in a more intermediate relationship between the saber-toothed cats and felids. The upper canines were not only shorter, but also more conical, than those of the true saber-toothed cats. These are referred to as being False sabre-tooths.

     As a rule, nimravids had shorter legs and tails than true cats. Their bodies were muscular and slung low to the ground.

     Another differences between nimravids and true felids would be invisible if one were slinking up to you. The various canals and foramina listed dictate the paths of various nerves and blood vessels in the skull, and the arrangement in nimravid skulls seem to be more primitive compared with true felids. Likewise, true cats have a two-chambered auditory bulla, which is a rounded bit of bone associated with the ear ; nimravids do not.

     Throughout the Oligocene, nimravids assumed all the predatory niches later taken by true cats. But by the beginning of the Miocene 23 million years ago) they had all disappeared in North America. For whatever reason, perhaps because there was an abundance of bearlike or canid carnivores of all descriptions present here at the time, there were no nimravids in North America for the next few million years. Felids also were missing and made their North American debut in the form of a small conical-toothed animal, Pseudailurus, about 17 million years ago.

     About 10 million year ago, Barbourfelis appeared in North America, presumably from Asia. Although Barbourfelis is now no longer considered a nimravid (!), it wasn't a true cat, either, so it is included on these close-but-no-cigar cat pages.

A Thumbnail Guide To Nimravids

Dinictis (40 million years ago/ Eocene) - found in North America, had a lithe body, short legs, long tails, and walked flat-footed (true cats walk on their toes).

Dinaelurus (late Eocene-late Miocene) - one skull found in Oregon in 1922. It had a short face and large nostril similar to a cheetah, so it is believed that it ran down its prey.

Dinailurictis (late Oligocene) - lived in Europe

Nimravus - (30-28 million years ago/ Oligocene) - found in France and North America, about 4 feet long and similar to a caracal. This small nimravid probably hunted birds and small mammals. Its dog-like feet had only partially retractile claws. The territories overlapped with that of Eusmilus, sometimes leading to conflict.

Eusmilus (30.5-28.5 million years ago/ Oligocene) - found in France and parts of North America, had long, flattened sabers and large flanges to sheath them. Eusmilus was about 8 ft. long.

Pogonodon (late Oligocene) - lived in North America and strongly resembled modern felines.

Quercylurus (late Oligocene) - lived in Europe. The size of a brown bear, Quercylurus was the largest nimravid known. It was muscular, walked plantigrade, and probably seemed very bear-like.

Hoplophoneus - (33-30 million years ago/ Oligocene) - related to Eusmilus, this one had scientists thinking it was a true sabertooth cat for years. Sizes vary from bobcat-size to jaguar-size. Hoplophoneus also had a bony flange to fit its curved canines.

Hoplophoneus is ready to pounce!

EUSMILUS and NIMRAVUS

Many nimravids lived about the same time and had overlapping territories. Not only were nimravids in competition with one other, they also considered any smaller nimravid prey.

One example found was that of an ancient conflict between Eusmilus and the smaller Nimravus. The 8 foot long predator attacked Nimravus. The Nimravus skull had a hole in it just large enough for a Eurosmilus fang! Not only that, the hole showed signs of healing, so that particular Nimravus escaped its attacker

The hole in the Nimravus skull was made by Eusmilus

Pogonodons: It's All In The Bite!

Pogonodons were similar in size and build to modern jaguars, but were nimravids. Of the five genera of cats present in the Oligocene Badlands Formations, these cats are among the rarest and least known. Equipped with large saber-like canine teeth, pogonodons were swift hunters that possessed the ability to climb while carrying large prey into the treetops. It is supposed that they were successful hunters that roamed a large territory.

Pogonodon was about the size of a modern-day mountain lion. The overall height was approximately 26 inches, and the length from tip of nose to tail was 5.5 feet. The skull was about one sixth smaller than a modern tiger's skull, roughly about 9.5 inches long.
Recent discoveries in the John Day Fossil Beds National Monument yielded some interesting evidence of convergence (parallel evolution) between pogodons and true felid sabertooths.

In this case, the dental enamel with a clear cementoenamel junction (CEJ) was preserved. The important gingiva provided tactile guidance throughout the pogonodon's bite and - more importantly - caused a reflex release if the cat jeopardised its sabers by biting too deeply (risking saber breakage), particularly while learning to bite.

The CEJ on the pogonodon is virtually identical to that of a felid Smilodon.

By using a mechanical Smilodon replica to inflict wounds on a bison carcass, representing different killing bite hypotheses, scientists experimented with the probable bite mechanism of sabertooths. Most notable was the extent of elastic movement in the hide and tissue of the bison as the bite progresses. In one flowing movement, the sabertooth can sever both the carotid and jugular in fractions of a second and be free of the prey without even re-opening the mouth. To do the bite properly requires constant tactile feedback provided by the CEJ, and adjustment of trajectory to avoid too deep or shallow a bite. As the bite progresses and the prey distorts there is risk of hooking the incisors and breaking the sabers.

Pogonodon might have hunted oreodonts, rhinos, three toed horses, or the occasional mouse deer. Oreodonts were fairly numerous and are sometimes described as a cross between a sheep and a big pig. The pogonodonts would have found them easy prey.

The consensus is: the nimravids evolved parallel to felids in many ways. They developed similar hunting (and biting) techniques and probably behaved as true felids.

Then, why are there no nimravids alive today? Possibly, when it came down to it, they were unable to compete with true felids. More importantly, these were sabertoothed animals and ALL the sabertooths - felid and nimravid - became extinct. The large prey these creatures hunted became extinct and the sabertooth cats and nimravids soon followed.

Original Pogonodon sketch by Mark Hallett

BARBOUROLFELIS

Barbourofelis were originally classified in with the nimravids, but now are thought to be closer to true felines. They still aren't quite cats, but now they are in their own unique classification.

Barbourofelis first appeared in Africa, then moved into Eurasia and, finally, into North America. Fossils have been found in Texas and Florida. When Barbourofelis arrived in North America, there were no nimravids or felids to compete with.

This huge animal is described as a bear-like lion. Massively muscled, it stalked the late Miocene (15 million - 6 million years ago). It had huge sabers and very prominent flanges to sheath them.

With its massive build, Barbourofelis was most likely an ambush hunter. Its powerful forepaws could pull the prey into the business end of its saber-teeth.

Indeed, the teeth were the largest of the various saber-tooth species and guaranteed that Barbourofelis reigned at the top of the food chain. To back up these huge teeth, its head had a flat profile caused by the expanded occipital region at the back of the skull. This allowed for the attachment of powerful neck and shoulder musculature, the driving force behind the sabers.

Barbourofelis Model by Paleocraft

YOUR GUIDE TO THE EPOCHS:

PALEOCENE EPOCH - 65 million years - 55 million years ago. It is the 1st epoch of the Cenozoic Era and marks the beginning of the "Age of the Mammals". Marsupials appear as well as the first creodonts. By the late Paleocene, Miacis - the ancestor of all carnivora - appears.

EOCENE EPOCH - 55 million - 33 million years ago. Rodents are the predominant small mammal. Early horse, elephants, and rhinos appear. The earliest meateaters, the creodonts, include several catlike species known as the oxyaenids. The middle Eocene gives rise to carnivores: the nimravids, but they aren't true cats yet.

OLIGOCENE EPOCH - 33 million - 23 million years ago. It is the third and final epoch of the Paleocene period. True felines (Proailurus) first appear.

MIOCENE EPOCH - begins 23 million years - 5 million years ago. It is the first epoch of the Neogene period. It is also the longest epoch of the Cenozoic Era, spanning 20 million years. The nimravids go extinct near the end of the Miocene. Pseudaelurus is the last common ancestor for felines and the machairodontinae. The marsupial Thylacosmilus appears in South America.

PLIOCENE EPOCH - 5 million years - 1.8 million years ago. It is the second and final epoch of the Neogene period. Hyaenas, thylacoleo, and early sabertoothed cats appear.

PLEISTOCENE EPOCH begins 1.8 million years ago and concludes with the end of the Ice Ages, about 10,000 years ago. In the early Pleistocene, Thylacosmilus -unable to compete with Smilodon - becomes extinct. By the late Pleistocene, the severe climate contributes to massive megafauna extinctions including the sabertoothed cats and thylacoleo.

HOLOCENE EPOCH - 10,000 years ago- modern times. The last sabertooth cats and cave lions became extinct near the beginning of this period. Most modern wild cats are dangerously close to extinction now.

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