Search Results for Machairodus

Machairodus pair: the intricacies behind a simple composition

One of the subjects I needed to depict for the Batallones exhibition was the sexual dimorphism in the Miocene sabertooth Machairodus aphanistus. In this species the males were considerably larger than the females, and the best way to reflect that fact was a simple illustration showing the relative sizes.

To illustrate the size dimorphism in Machairodus I just scaled up the same drawing to fit with the sizes of a very large (presumably male) and a very small (presumably female) adult individuals from Batallones 1 based on the measurements of their long bones (in this case the humerus)

But what would it be like to see a Machairodus couple in their environment? Would we see a striking difference as with modern lions or something more discreet as in leopards? In terms of its external appearance the lion is clearly the most dimorphic among living cat species, but surprisingly, in terms of body size the leopard is even more dimorphic. And yet, if you see an adult leopard out in the African bush, you may have a hard time trying to sex it unless the cat obligingly raises its tail. Some older female leopards can be so stocky and muscular that they would pass for a male, but then older male leopards often have very thick necks with a dewlap of loose skin hanging from their throats which make it easier to recognize them. Among tigers, the males not only are larger but they usually have a thick growth of long hair on the sides of their heads, a feature that is mirrored to some degree in other cat species.

What then about Machairodus? We have no evidence to infer a dramatic external feature like the lion male, not only because the lion is the outstanding exception among all living cats but because it is likely that the evolution of its mane has at least something to do with its similarly exceptional social structure. So for Machairodus I have inferred a similar coat for both sexes, although I have given a somewhat longer “beard” to the male. Also I have depicted the male yawning in order to show its large canines. After all, as in other cats, not only the male is larger than the female but it also has relatively larger canine teeth, and displaying them would be an important part of its body language.

For this illustration I decided to do a very simple composition with the two animals resting on the ground, and I quickly defined it with a rough pencil sketch

In a second pencil sketch I went into a little more detail, especially in the head of the male whose facial expression is more complex to portray

For the final version I used my computer 3D model of the skull of Machairodus, rendering it in the same views as the sketched heads so that I could check the proportions

Like other sabertooth cats, Machairodus had a somewhat longer and narrower skull than a modern cat of similar size. This difference would be partly masked in life by the thickness of soft tissue around the skull, but still it would be noticed, at least subtly.

In the final composition, the counterpoint to the shapes of the cats is provided by the fallen tree just behind the animals, but at one point I felt I needed one more, nearer plane in the picture. As an experiment I quickly added another fallen branch in the foreground, but I was not quite convinced by the effect

Finally I decided to delete the foregorund branch and leave the original, cleaner compostion

Was this the best option? Well, as in many other cases, I wouldn´t say for sure. I simply followed my instinct while trying to make choices within the limited time frame of this assignment. I had a large series of complex illustrations to do and a tight deadline, which, looking back, sometimes is a good thing. When you are a perfectionist of sorts, agonizing endlessly about your composition choices is a very real danger, so that limited time can be, ironically, the lesser of two evils!

Machairodus hunting an Hipparion: from Raw Sketches to Final Art

One of the many illustrations I prepared for the new exhibition about the Batallones fossil site shows the large sabertooth cat Machairodus aphanistus hunting a three-toed horse of the genus Hipparion.
I needed to illustrate the key moment of the killing bite, and as a result the predator and prey duo make a dramatic but not especially dynamic ensemble, with the horse being pinned to the ground by the weight of the predator. I had previously rendered this action as a pencil drawing on a white background, but this time I wanted to place the animals in their habitat, showing the kind of environment that allowed the sabertooth to creep on its prey taking advantage of cover. But how to create a dynamic environmental composition when the center of attention is at the same time violent and static? Placing the kill in the center of the frame would neutralize the composition, creating a sort of implosion where everything else becomes superfluous.

My first decision was thus to move the cat and horse, and especially their heads which would attract all attention, away from the frame’s center. This decision at the same time made the composition more dynamic and threw it out of balance so I included a second cat in the scene to put something on the empty left side. In my hypothetical story, the hunting cat would be an adult female, while this second individual would be a grown cub, of the kind that sometimes assist and sometimes ruin their mother’s kills. Such a scenario is derived from the behavior of modern big cats and it allowed me to make the presence of a second large cat compatible with the likely solitary life of these sabertooths.

In this first raw sketch I quickly outlined the masses of the three animals, and used several trees to organize the rest of the space in the frame. Looking at the draft I felt that the second cat had perhaps too much importance in this composition, how to solve this problem?

In this second pencil drawing I attempted to leave the second cat in shadow in order to center the attention on the kill, but even with such a quick sketch I noticed that there was enough intensity on the predation without further highlighting it. The second cat should retain its share of the sunlight

In this third sketch I calculated the effects of perspective more carefully and found that I could place the second cat at a distance where it would look conveniently smaller than the hunting cat. With the animals approximately placed in the composition I began to work in the digital painting

As the painting began to take shape I found that the trees were shaping the composition a bit too strongly. Drawn with a few light pencil strokes, they seemed to arrange the space conveniently, but when those lines became solid branches they almost appeared to be enveloping the animals, like the sinister “Old Man Willow” capturing the hobbits in The Lord of the Rings… So I trimmed the lower branches leaving some breathing space for the animals and creating a corridor for our eyes to look into the mid-distance. Other changes included to block the view of the distant hilltop (which resonated too much with the shapes of the animals and seemed also to compete for attention) and to replace the tree trunk in the left side foreground with a more modest shrub.

In the finished painting I added a marten-like mustelid climbing on the tree trunk on the right, an element that further dilutes the tension. All in all I tried to compensate the violence of the kill with an apparently matter-of fact distribution of the elements in the composition so it would not look overly dramatic

The random patterns of light and shadow on the ground also intend to treat the story’s “stars” almost as just two more objects placed in the landscape, like something you could see while driving along in your safari vehicle. I don’t claim that this anti-dramatic treatment is the best solution for this painting, but it is what my instincts dictated as I went along. Following your instincts is in no way an infallible recipe for success, but as an artist it is still the best compass you have for finding your way through the conflicts of a complex work!


When you spend time in the African savannah you are surprised to see how relaxed the herbivores can be in the proximity of the big cats. Zebras and antelopes don’t stampede at the mere presence of a lion, but they rather observe it. Information flows in both directions, and the ungulates know how to read the body language of predators. A feline walking casually is no cause of panic, and the potential prey just look at it cautiously until it disappears. And it makes sense, because if zebras had to be in a constant state of panic at the possible presence of a predator, stress would kill them even before the predators would. For us humans as well, irrational fear of predators is probably something that developed once we abandoned our life as hunters-gatherers to become Neolithic farmers. Before that, cautious respect and a keen interest in the predators would be a far more useful attitude than panic.
As a sabertooth freak, I often imagine what it would be like to travel back in time and meet my favourite predators from the past. If I were in a B movie, a succesion of screams and chases would follow, and my survival would depend on being the star of the film or a mere sideshow, so I would really stand little chance of survival! But in the natural world, I should rather try to follow the example of the zebra and read the cat’s body language before running.
To see an adult Amphimachairodus walking your way would be in impressive sight by any standards. Tall as a lion, it would walk with a cat-like supination of the forepaws, although less exaggerated than in a lion: the structure of its elbow and wrist joints tell us that much. Free-swinging shoulder blades would move up and down as the cat stepped towards us. But the animal’s head would be subtly different from any modern cat’s. The face was narrower, with slightly smaller eyes looking less frontally, somehow intermediate between a lion’s and a wolf’s in terms of relative size and position. The muzzle was long and high but also narrow, with blade-like upper canines showing discretely beyond the upper lips.

Reconstruction of Amphimachairodus in frontal view. The animal was as tall as a lion with a distinctly cat-like walk, but it had a peculiar narrow head with a high and narrow muzzle and blade-like upper canines showing beyond the upper lips
amphimachairodus-front low res

Concerning body language, if the cat is walking upright and with a casual cadence, you have reason to think it is just minding its business rather than stalking you. A relaxed mouth further indicates lack of aggression, but ears pointing slightly backwards are less simple to read. In the general context of a relaxed animal they don’t mean much, but it could be the sabertooth is not very happy about something. Better observe it for a few seconds and see what those ears do, but remember that any part of the animal’s body generally works as a part of the whole, and if the cat is in an aggressive mood there will be other signs apart from those ears to show it…
Amphimachairodus lived a little too long ago for our bipedal hominin ancestors to have come across it, but other sabertooths, such as Homotherium and Megantereon, were familiar elements of their world. I am sure that body-language reading was more important than panic as a reaction to their presence. But timing is everything, and surely there was a right time to panic as well!


Some eight million years ago, during the late Miocene, much of Eurasia underwent dramatic environmental changes, with a reduction in the previous expanse of forests and a predominance of open woodlands and savannah-like landscapes. This part of the Miocene period is known in Europe as the Turolian.
The Turolian plains were inhabited by herds of three toed-horses and many kinds of antelopes, which together with a diversity of giraffids, rhinos, and proboscideans, would turn much of the old continent, to our eyes, into a gigantic Serengeti of sorts. That vast array of herbivores was not free of predation, and the lion’s share corresponded to one of the most impressive sabertooth genera ever: Amphimachairodus.
Probably originating in Asia, Amphimachairodus spread like fire across the continents, becoming the dominant large carnivore in Europe and North America and eventually entering Africa and reaching as far South as the Cape province. Nothing could stand in its way. What was the key to such success? A close relative of Machairodus, Amphimachairodus took the adaptations of its older cousin one step further, not only by developing longer, more flattened and more coarsely serrated upper canines, but also by refining the adaptations of its skull, mandible and neck for a super-efficient kind of killing bite. Fully as large as a lion, Amphimachairodus not only had access to very big prey, but it also was dominant over any other predator in its habitat.

The skull of Amphimachairodus giganteus, shown here in four different views, reveals the refined adaptations for the sabertooth type of killing bite, known as the “Canine shear-bite”
amphimachairodus skull views low res

A less well known side of the success of Amphimachairodus was diversity. Subtle differences between species are not always easy to tell from the fossil record, but it is obvious that there existed more than one species of this sabertooh genus during the late Miocene. The type species, A. giganteus, was widespread in Eurasia, but others have been desccribed in China, North America and Africa. And with diversity come different adaptations and even behaviours. Populations of A. giganteus living in open environments, in direct competition with clans of the large hyena Adcrocuta, would probably develop some sort of social behaviour in order to defend territory, females, cubs, and kills. But other species within the genus may have led solitary lives in more wooded environments, much like the modern tiger does. Just let us bear in mind that the genus Panthera today includes a diversity of adaptations which we would hardly be able to tell from their bones alone. Lions, tigers, jaguars, leopards, snow leopards, each one has its unique solutions to cope with the challenges of its ecological niche, and so would the sabertooths.

The impressive teeth of Amphimachirodus would give additional intensity to any facial expression. The interplay of the complex facial muscles, for which all cats are notorious, would allow a precise transmission of mood to conspecifics, and why not, to rival species such as the hyaenas. The expression shown in this illustration clearly says “don´t mess with me”!
amphimachairodus snarling low res

Fortunately, the fossil record provides more than just skulls to gauge at the adaptations of Amphimachairodus, as we shall see elsewhere.

If you want to know much more about these magnificent beasts, get my book “Sabertooth”!
sabertooth cover low res

Brave New Worlds: The Holarctic reign of Machairodus

During the Miocene, North America was home to an impressive array of sabertoothed predators. Some of them belonged to the Barbourofelidae, a family of carnivores that developed extreme sabertooth adaptations and became extinct during the late Miocene; others were true sabertoothed cats, members of the family Felidae.
Among the latter, there were several species that look superficially very similar to one another, and paleontologists have a hard time trying to sort out their relationships. Were all these species part of a single, native American lineage spanning much of the Miocene period? or perhaps some of them arrived to North America from the Old World as part of succesive immigration events?
This may sound like a very technical issue, but it touches the very core subject of sabertooth evolution: we know that the sabertooth morphology is an adaptation for a very specific killing technique, but, how much of that morphology is the result of shared ancestry and how much is the result of convergence?
After this somewhat technical introduction, let me introduce to you an amazing sabertooth cat: Machairodus catocopis. This predator had the approximate size and body proportions of a modern tiger, but it was armed with elongated, laterally flattened upper canine teeth with coarsely serrated margins that allowed it to kill large prey almost instantly through massive blood loss. It also had a huge “dewclaw” that it used for literally hooking its prey.

Here is a reconstruction of Machairodus catocopis based on the exceptional fossils housed at the American Museum of Natural History
machairodus catocopis-baja

Years after its original description, this species was removed from the genus Machairodus and assigned to Nimravides, a change that reflected the belief that it was part of a native lineage of cats that had evolved in North America for many milions of years. Those changes in classification had been made on the basis of fragmentary fossils, but several years ago at the American Museum of Natural History (New York) collections I came across a couple of undescribed specimens that were amazingly well preserved, and they seemed to me strikingly similar to the fossils of Machairodus aphanistus that we were finding in the fossil sites of Cerro Batallones, in Spain.
Now in collaboration with my colleagues Manuel Salesa and Gema Siliceo from the Museo Nacional de Ciencias Naturales (CSIC) I have finally been able to look in detail at the anatomy of those wonderful American fossils, and we have found that the similarities with the Spanish specimens go very deep indeed. This study, now published in the Journal of Vertebrate Paleontology, clearly indicates that Edward Drinker Cope (back in 1887!) was right from the start to classify this animal in the genus Machairodus: it is so closely related to the Batallones sabertooth that if we found its fossils in a Spanish site we would consider it just a slightly more advanced form of the same group. The geological ages of the two populations are consistent with the possibility that the ancestors of M. catocopis arrived to North America as part of a migration wave from the Old World. The original migrant must have been almost identical to the Batallones cat: an immensely powerful animal that had the potential to invade continents and rule as top predator thanks to the combination of a versatile feline body plan and a pair of precociously specialized scimitar-like canines.
By the way, don’t bother to look for Machairodus catocopis in my upcoming book “Sabertooth”. The book went into press before our new paper was published, so I had to stick to the previous classification and call it “Nimravides catocopis”…

Here is the title of our new pubication:
Antón, M, M. J. Salesa and G. Siliceo 2013. Machairodont adaptations and affinities of the
Holarctic late Miocene homotherin Machairodus (Mammalia, Carnivora, Felidae): the case of Machairodus catocopis Cope, 1887. Journal of Vertebrate Paleontology 33:5, 1202-1213

You can check it in the JVP page:

Doomed predators: conveying the drama of carnivore entrapment in Batallones 3

Yet another of the illustrations I did for the great Batallones exhibition intended to depict an entrapment event at one of the carnivore traps, concretely Batallones 3. Some distinctive features of Batallones 3 are the large number of fossils of the larger sabertooth Machairodus aphanistus, which is the single most abundant species at the site; the presence of the bear Indarctos arctoides (absent in Batallones 1); and the abundance of giant tortoises of the species Titanochelon bolivari.

I planned a simple scene which showed these 3 main elements within the cavity, and I needed to gather all those big animals in a relatively small, closed space while still maintaining a sense of depth. One subtle aspect to consider was the angle of view. Put in other words, if I were a time-traveler and I could enter the cavity and take a picture of the scene, what lens should I choose?

In my first rough pencil sketch I chose an imaginary wide-angle lens, meaning that I got very close to the dead tortoise and sabertooth in the foreground and the bear in the background appeared to be farther away and thus looked smaller. This option created greater depth but it could make the cavity look too spacious

In a second pencil sketch I chose an imaginary 50mm lens or even a moderate telephoto. If I had been at the scene, this means I would have to step back from the smelly tortoise carcass and the anguished sabertooth (maybe hitting my head with the low roof of the cavity) in order to fit everything in the frame. The bear would look proportionally larger, and the cavity smaller

I choose the latter option and went ahead to block some of the shades with a sort of digital watercolour

When I tackled the final digital painting and the scene became more solid, once again I got the impression that the the viewer and animals were crowded in a too small room, so I corrected the view until I got something in between the first two options

In order to give a little more depth to the scene I used some rays of light coming from the roof opening to suggest layers of atmosphere. Those effects, together with the somewhat “heroic” pose of the sabertooth give the scene and adventure feel, something like the cover of a comic book. But still the real scene would have been oppressing, so I devoted quite some time to dwell on the effect of the mud splatters on the cat’s fur or the flies buzzing around the rotting tortoise, all reminders of the down-to-earth drama that led to the eventual preservation of the fossils which we finally find in the site.

Sabertooth vs Bear-dog and Composition vs. Design

The last illustration I did for the Batallones exhibition correspons to a concept that had been on my mind for many months: a conflict between the two most fearsome predators from the site, the sabertooth Machairodus and the amphicyonid Magericyon. Only after the “warming up” of all the work in the rest of the pieces did I feel I was ready to tackle this one, and still it proved to be a challenge, not only for the composition itself but because of format limitations.

The image was intended to serve as cover art for the exhibition’s companion book, which meant a vertical format, but it would also serve other secondary purposes, so I had to extend the scene to the sides to allow it to function as a horizontal composition. Still, all the vital elements had to be grouped in the center so that the book cover would not look cropped up.

In my first pencil sketch I tried to fit the elements of the drama in the center. This is essentially NOT the way I use to compose. I like to place important elements on the sides of the frame so they will “pull” and create a tension that resolves somewhere in between (although never dead-center). I was beginning to solve the parts that would fit in the cover frame, but the whole composition felt lame.

In the second sketch I incorporated a third gomphothere approaching from the right. Depending on the amount of cropping, this animal might not even appear on the cover but I needed to expand a little from the center. I also incorporated some distant woods that put some welcome mass on the sides of the frame. Still, I felt the thing was lacking cohesion, with the elements in the center not having enough pull to keep the composition together.

In the third sketch I incorporated some trees that allowed me to organize the three-dimensional space of the scene. I also re-arranged the approaching gomphotheres so as to leave some breathing space in the vertical right above the dead beast. At this stage I decided to start with the digital painting.

In the early stages of the painting I felt like I was getting a grip on the composition but then we had a production meeting, and the design people showed me a preliminary placing for the titles. It was clear that the trees would provide too intense a background for some of the lettering.

In the next stage of the painting I had already deleted the nearby trees. The only elements I could use to organice space (besides the animals themselves) were the distant vegetation, the clouds, and the patches of shadow. Also I had added some more painting on the top and bottom to leave room for more titles. But then I heard from the desgin people again: they would be using the piece for a big canvas banner hanging outside the museum building, and it needed to be very wide, so I had to add even more painting on the sides.

In the final version the animals look rather crowded in the center of the wide-angle landscape…

…but seeing the huge banner on the museum wall, choke-full of titles and institution logos, I admit there was no way around the need to zoom-out (although it took me quite a few hours of painting extra grass and bushes!)

The book cover, for which the whole thing was done to start with, still manages to encompass all the action within the frame.

For me, this is an example of an assignment that required sacrificing “pure” composition values in favor of a more “applied” approach. Demanding as these exercises can be, they are good for keeping us alert and humble as artists!

Swift pussy cat: Batallones’ little feline wonder revealed

The fossil sites of Batallones provide amazing insights into the predator guild of the Vallesian epoch (Late Miocene, 9,5 Ma) of Spain, and are best known for the incredible collection of fossils of sabre-toothed felids, including the leopard-sized Promegantereon and the lion-sized Machairodus. A less known fact is that the other “half” of the felid family, the felines (or “conical-toothed cats”) were already present and represented by a respectable sample of fossils at the site.
Those early relatives of our modern lions and tigers posed no threat for the sabertooths, because they were all much smaller animals. Two species are known from the site, the lynx-sized Pristifelis attica and the wildcat-sized Leptofelis vallesiensis. Years ago, in our initial description of the animal we called it Styriofelis vallesiensis because its dentition was very similar to that of earlier, Middle Miocene felines classified in the genus Styriofelis. However, our recent analysis of the postcranial bones of the small feline from Batallones has revealed unexpected differences with those earlier animals.
The middle Miocene Styriofelis turnauensis combined peculiar dental traits (in particular the retention of milk premolars in adult life) with a skeleton adapted for climbing, with short, robust limb bones. Such a skeleton can be considered “primitive” for felids, because the ancestral members of the family were mostly arboreal creatures. The small cat from Batallones shared with Styriofelis the retained milk teeth, but its limb bones now reveal a surprisingly early adaptation for fast, efficient locomotion on land. This condition almost mirrored the one seen in modern animals like the wildcat, but it most likely evolved independently, because the particular dental features preclude Leptofelis from being an ancestor of the modern species. In fact, the skeleton of the Batallones small cat is in itself a mosaic of features, including the presence of a well-developed quadratus plantae muscle inserting on the ankle bone. This muscle has an important function in climbing and it shows that in spite of being a proficient runner, Leptofelis vallesiensis could climb better than most modern cats, both to escape bigger predators and to catch small prey in the high branches. Also the hind limb was especially long and the knee articulation resembled that of modern small carnivores that are excellent jumpers and climbers, such as the genet. It is possible that Leptofelis used its leaping ability to capture small prey such as rodents and birds while foraging on the ground, like modern servals or caracals do. This unique combination of features convinced us of the need to create a new genus for this cat, and we coined the word “Leptofelis”, meaning “swift cat”.

In this illustration we show some of the preserved bones of Leptofelis superimposed to a hypothetical reconstruction of its complete skeleton.

There are many things we have learned from this study. On one hand, the early diversity of felines is greater than was thought some years ago, when virtually all fossil felines from the late Miocene were classified in the extant genus Felis. On the other hand, we see that the adaptations of feline cats for running not only appeared more precociously than thought, but in fact evolved several times independently. Also important is the fact that the postcranial skeleton, often overlooked in systematic studies, can provide decisive evidence for the proper classification of an extinct animal. And, finally, if we look at the larger picture, it seems that the combination of the small size of the early felines, the need to escape from larger predators, and the presence of vegetational cover in their environments probably provided the right adaptive pressures which led (more than once) to the evolution of the versatile body plan that we see in modern cats.

Here is a reconstruction of Leptofelis in the flesh. The coat colour patter is unknown in this animal and here it is reconstructed on the basis of species such as the marbled cat, whose coat markings appear to represent the ancestral patter for all living felines.


You can check our original research paper in this link:

From sketch to painting: lighting

Leafing through folders with old drawings I found a few rough sketches for two paintings I intended to include in “The Big Cats and their Fossil Relatives” (1997). Back in those days photo references were much harder to come by and I had to relay more heavily on my clay models, which I set in the pose of the planned painting and put under a lamp to mimic the desired lighting conditions.
During the late 1980s documentary viewers around the world were awed at the athletic feats of the tigers of Ranthambore, especially the formidable male nicknamed “Genghis”, who used to charge through the shallow water in pursuit of sambar deer. It was only natural that I wished to paint a similar scene with a different cast of characters, in particular the agile, tiger-sized sabertooth Machairodus catocopis and the strange artiodactyl Procranioceras, both from the late Miocene of North America.

In my earliest sketches for this scene I showed a different prey, Syntethoceras, which looked conveniently bizarre, but then I found that it apparently did not coexist with M. catocopis in the same fossil sites.

My next sketch already showed Procranioceras in place, but I still did not explore the matter of lighting in much detail.

Then I finally took the time to model Machairodus in the desired pose and place the figurine under the lamp to see the play of light and shadow.

The final painting took me ages to finish and indeed it did not appear in “The Big Cats”. It would only be published in 2004 in “The National Geographic Book of Prehistoric Mammals”.

Another sensation for wildlife documentary lovers back in the 1980s was the revelation of the intimate life of the white wolves of Ellesmere island, then filmed and photographed for the first time. Those predators chased their prey, from hares to musk oxen, in the barren expanses of the high Arctic, and in my mind the connection was made with the lightly built Beringian sabertooths of the genus Homotherium. Paleontologist Bjorn Kurtén had hypothesized that those animals would be black to match the coat color of their main prey, the woolly mammoth, but I found at least as likely that they would be white to match the winter color of their environment, just like the arctic wolves.
So I set to paint a scene with white predator and white prey inspired in those breathtaking Ellesmere images. I wanted to show my subjects under the dramatic light of the low arctic sun, and once again I had to model my creatures in clay and light them. The horns of the Dall ram were especially complex objects and I would have been at a loss to paint them without the figurine.

In this sketch I set the creatures in the composition.

In this quick study I concentrated on showing light and shadow as discrete patches.

In this case the final painting did find its way to “The Big Cats”!.



In 1960, at a time when little was known about the anatomy and body proportions of bear-dogs, American paleontologist Stanley Olsen described a wonderful collection of postcraneal fossils of Amphicyon longiramus, from the Miocene site of Thomas Farm in Florida. Olsen’s paper profiled a kind of predator with no living counterpart. With a body size comparable to that of a modern brown bear, Amphicyon had a longer and more flexible back and a long, heavy tail. Its dentition resembled that of a dog more than that of a bear, and was better suited for consuming meat and bone, while still allowing the animal a varied diet.

Here is my reconstruction of Amphicyon longiramus, based mostly on Olsen’s descriptions of the Thomas Farm material
a-longiramus-recons-2 low res

In the middle Miocene, when sabertooth cats hadn’t yet attained their full size and dominance, amphicyonine bear-dogs like Amphicyon were the undisputed ruling predators, both in Eurasia and in North America. Although they could not run especially fast or long, they were capable of ambushing large animals using a vaguely cat-like hunting style, and then they could use their great muscular strength and powerful canine teeth to bring down and kill their prey. But with the late Miocene the rule of the bear-dogs was challenged by the appearance of such powerful felid sabertooths as Machairodus. Later relatives of Amphicyon, such as Magericyon, (best known thanks to the fossil sample from Batallones in Spain)adapted to the new times by becoming somewhat smaller and developing more specialized dentitions for killing and consuming large prey efficiently. But there was no resisting the empire of the machairodonts, and near the end of the Miocene the bear-dogs disappeared for good after many million years of successful evolution.

Here is the reference of Olsen’s papers:
Olsen, Stanley J. 1960. The fossil carnivore Amphicyon longiramus from the Thomas Farm Miocene. Part II, Part II. Cambridge, Mass: Harvard University, Museum of Comparative Zoology.