Modern dogs differ from other carnivores in one interesting anatomical feature: they have a “nuchal ligament”, a string-like structure that runs along the dorsal part of their necks and allows them to support the weight of the head with little muscular effort. Dogs share this feature with ungulates, but there are differences in detail: while in ungulates the ligament extends from the spines of the thoracic vertebrae to the back of the head (hence the name “nuchal”, meaning “attaching to the nape”), in dogs it only runs as far ahead as the second cervical vertebra (the axis), so the term nuchal ligament is somehing of a misnomer here. But, at any rate, what would a carnivore want a nuchal ligament for? Such an adaptation makes sense in a cow or a sheep, who spend many hours grazing with their heads down, an activity that calls for some passive mechanism to save the muscular effort of supporting and then lifting the weight of the head. But carnivores don’t graze, do they?
Well, what dogs do is track scent trails. They walk and trot for long distances, nose close to the ground, as they search and follow their prey’s smelly paths. And they also happen to be relatively long-legged carnivores, which implies they need a long neck for their snout to reach the ground as the animal trots. So the neck of a wolf, jackal or coyote is proportionally very long, but some of the muscles that turn it to the sides and pull it up are relatively reduced, compared to other carnivores, partly because their role is taken by the nuchal ligament.
Here is a drawing of the neck of a wolf (Canis lupus), showing the skull and vertebrae (top) selected deep muscles (middle) and more superficial muscles. See how the “nuchal ligament” actually doesn´t reach the nape, just the back of the axis vertebra.
But, have the necks of dogs always been like that? Several years ago, while working on the reconstructions of fossil dogs for our book “Dogs: their fossil relatives and evolutionary history”, Xioaming Wang, the late Dick Tedford and myself looked in detail at the anatomy of the fossil dog Aelurodon, from the American Miocene. Fortunately there is an amazing collection of fossils of these animals at the American Museum of Natural History in NYC, so we had all the information we could hope for. While studying the cervical vertebrae I found something strange about them: they somehow resembled the vertebrae of a big cat, such as a leopard, more than they did the same elements in a wolf. Concretely, the vertebrae were relatively short, and the processes for muscle attachment were proportionally larger, projecting farther away from the vertebral body. When I assembled the bones to create a reconstruction, the neck looked suprisingly short, and when I reconstructed the musculature of the neck on the basis of the shape and position of attachment areas, it was evident that this animal had a more powerful neck than a wolf of comparable size. There is no obvious evidence for the presence or absence of a nuchal ligament, but the morphology of the back of the axis, where the ligament would attach, is rather different from that of modern dogs. Also, the short neck and its powerful muscles would make the function of such a ligament rather irrelevant.
Here is a reconstruction of the head and neck of Aelurodon. The morphology of the cervical vertebrae (top) implies a relatively short neck, while the shape of muscle attachment areas speaks of very strong musculature (center). Both features resemble the necks of modern big cats. When external layers are added, we see that the animal’s head and neck woudl look powerful and socky (bottom)
These anatomical differences must have implied differences in behavior, but it is not clear what differences those would be. Given the simmilarities with a cat’s neck, it is tempting to assume a more cat-like hunting style for Aelurodon, implying that the predator was more able to handle its prey individually, using its paws to restrict its struggles, and using its neck as a base for delivering a more precise killing bite, a bit like big cats do. Also it is possible that trotting for miles in search of scent trails as some modern dogs do was a less important part of its behavioral repertoire. But it is also possible that the predatory behaviour of Aelurodon was essentially similar to that of modern wolves and it simply had not evolved some of their anatomical refinements.
A broad comparison of neck morphology in fossil dogs revealed to us that the first taxon to clearly show a modern wolf-like neck anatomy was the late Miocene and Pliocene genus Eucyon. This animal also developed proportionally longer forelimbs than any of its earlier relatives, probably reflecting an adaptation to drier, more open environments, and wider foraging areas. So it would make sense to think that a modern foraging stlye in these members of the dog subfamily caninae was accompanied by the development of a modern forelimb and neck anatomy.
Only additional research will take us closer to solve these riddles, but one thing is certain: just like in the cat family, fossil dogs reveal a diversity of adaptations that we could hardly suspect by looking only at the living species. And the dramatic difference that we see today between dogs and cats could have been a bit more blurred in the distant past!
To learn much more about dog evoution and fossil record, check our book:
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.
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.
More than 3 million years ago, somewhere in Northeastern Spain, a volcano exploded and created a large crater. With time the crater was occupied by a lake, known by geologists as a maar. Today, the lake is dry and the crater walls have been largely levelled by erosion, but an exceptional fossil site bears witness to the events that took place there. The site, called Camp dels Ninots, is close to the village of Caldas de Malavella in Girona.
Maar lakes often create remarkably beautiful scenery, with their encircling walls covered by forests, but some of them hide something more sinister. One example is lake Nyos in Cameroon, which in 1986 emitted a large cloud of carbon dioxide that killed thousands of people and animals. Such toxic gas emmissions occur because the pocket of magma beneath the lake leaks the carbon dioxide into the water, and perturbations such as those caused by a landslide can cause the gas to emerge with disastrous effects.
Three million years ago around the Camp dels Ninots maar lake, a rich fauna thrived in a subtropical environment, much warmer than today. Rhinos, tapirs and heavy antelopes crossed the forests and came down the crater walls for a drink at the lake margin. But several of those animals died mysteriously at the shore, and their bodies floated into the lake where they ultimately sank. Their skeletons, completely articulated, got exquisitely preserved as fossils, without any trace of having been disturbed by scavengers. A likely explanation is that the lake belched a cloud of toxic gas, instantly killing all the animals along the shore.
As often happens, the animals’ doom was the paleontologists’ blessing, since the death of so many creatures led to their pristine preservation. As the local authorities planned for an on-site exhibit, I was asked to create several reconstructions of the Pliocene environments and fauna of Camp dels Ninots, including a scene showing the hypothetical origin of the fossil accumulation.
And here is the finished painting that can be seen today at the fossil site
The scene shows antelopes of the genus Alephis and a rhinoceros of the genus Stephanorhinus on the shore, already showing signs of intoxication, while a tapir (Tapirus) lies on the ground, already dead. The bodies of other antelopes float in the lake while a pair of cormorants that happened to fly too low are already falling.
This and other reconstructions of the fauna and environments of Camp dels Ninots can be seen as part of the outdoors exhibit. Thanks to the findings made at the site, we now know a lot more about the anatomy of several species of Pliocene mammals, but, alas, no sabertooth skeleton has been found there as yet. But I don´t give up hope.
In central France, another Pliocene maar lake fossil site, a little younger in age than Camp dels Ninots, has been known for about a century, and it has yielded the most complete skeletons known to science of the typical sabertooth cats of the Pliocene: Homotherium and Megantereon. For several decades the French site, known as Senéze, was exploited without any serious excavation methodology, so we don´t know much about the taphonomy of those early finds. But since the 1990s, new field campaigns have yielded more accurate data, suggesting that the fossil mammal skeletons from Senéze accumulated as landslides coming down the crater walls trapped the animals and dragged their bodies to the lake.
I took this photo of the mounted skeleton of Megantereon from Senéze, exhibited at the Natural History Museum of Basel (Switzerland), back in 1990. All other findings of Megantereon fossils are more fragmentary, so it is only thanks to the exceptional conditions of the volcanic maar lake that we know nearly every bone of this sabertooth cat.
Only a portion of the ancient lake shore at Camp dels Ninots has been excavated this far. Sabertooths like Dinofelis diastemata, whose skeleton is mostly unknown, probably inhabited the area at the time, so it is not impossible that the next excavation will yield an amazingly preserved specimen…who knows?
Volcanic eruptions have provided the right conditions for the preservation of some of the best sabertooth fossils known to science, and not only beacuse of maar lake sites. If you want to know more about volcanoes and sabertooths, read my book “Sabertooth”! http://www.amazon.com/Sabertooth-Life-Past-Mauricio-Ant%C3%B3n/dp/025301042X/ref=sr_1_1?s=books&ie=UTF8&qid=1459250381&sr=1-1&keywords=sabertooth
Visit the on-site exhibition at Camp dels Ninots:
It was once thought that the enlarged upper canines of sabertooths evolved as an adaptation to pierce the skin of “pachyderms” such as elephants or rhinos and other gigantic herbivores of the past. But if we need just one proof against such an argument, then the nimravid Eusmilus should be it.
Members of the genus Eusmilus lived in Eurasia and North America in the Oligocene, millions of years before any true felid sabertooth ever evolved. But if we look at the skull of a well known species, such as Eusmilus bidentatus from France, we find that this early animal had taken its sabertooth specializations to a degree not seen even in the late Pleistocene felid Smilodon. Eusmilus not only had very elongated upper canines, but its whole skull was deeply remodeled to increase the biomechanical efficiency of its killing bite. But, while Smilodon was considerably heavier than even the largest modern cats, Eusmilus bidentatus was… smaller than a modern lynx!
Here is a life reconstruction of Eusmilus bidentatus based on Oligocene fossils from France. The animal was heavily muscled and powerful but with a shoulder height of about 45 cm it was shorter than a modern lynx
With its modest body size, Eusmilus could not even dream of attacking any of the thick-skinned behemoths that roamed the Oligocene woodlands and prairies, including many kinds of relatives of the rhinoceros. Eusmilus‘ elongated canines meant that, even with the additional gape provided by its specialized mandibular articulation, the clearance between the tips of upper and lower fangs was similar to that of a lynx. The size of the animals to which it could apply its killing bite was consequently rather small. It is thus evident that the sabertooth adaptations of this predator were not aimed at hunting giant, thick-skinned herbivores, but rather to the quick and efficient dispatching of small and medium-sized prey thanks to a killing bite that caused rapid death through massive blood loss, thus minimizing the danger of a trashing prey escaping or wounding the predator, or both.
Another consequence of its small size was that Eusmilus, like many other kinds of small sabertooths through the Tertiary, was not nearly the dominant predator in its environment. For millions of years, hyaenodonts, bear-dogs, and even the omnivorous pig-like entelodons, have abused these sophisticated but small sabertooths, and stolen their rightful prey.
Small as it was, Eusmilus was not the tiniest sabretooth to evolve. Other species of the genus, like the American Eusmilus cerebralis, was even smaller, and so was the Eocene creodont sabertooth Machaeroides, not taller than a house cat. It is funny to think how nice a pet one of these miniature killers would make, but leaving it to roam in the neighborhood could result in more bloody incidents than any modern house cat can cause…
Want to learn much more about Eusmilus and other mini-sabertooths? Get the award-winning book “Sabertooth” and have your fill of long-in-the-tooth predators! http://www.amazon.com/Sabertooth-Life-Past-Mauricio-Ant%C3%B3n/dp/025301042X/ref=sr_1_1?s=books&ie=UTF8&qid=1454418468&sr=1-1&keywords=sabertooth
Hyenas have long been the victims of human prejudice and superstition, from ancient tribal tales to “The Lion King”. That is a pity because it gets in the way of our perception of a group of amazing animals with incredible adaptations for their ecological niches.
Lions sometimes have a hard time defending their rightful kills against large hyena clans, but quite often it is the hyenas who lose their own prey to opportunistic lions. Such dynamics are not new, and there is every likelihood that the woodlands and prairies of the Miocene, Pliocene and Pleistocene witnessed comparable conflicts quite often.
In the Old World Plio-Pleistocene, it was the lion-sized sabertooths of the genus Homotherium who had to deal with the challenges of living next to a most impressive hyena: Pachycrocuta brevirrostris. This animal was considerably larger in its linear dimensions than the living spotted hyena, but it was also more robust, so its body mass would have been much larger.
P. breviorrostris shared all the adaptations of modern hyenas for cracking bones (massive, blunt premolar teeth, robust skull with a domed forehead) and for carrying large pieces of carcasses over long distances (long, well muscled neck, large scapula with a flat articulation for weight transmission, shortened back and hind limbs for stability). But its massive size took those adaptations to a different scale, and certainly it made the giant hyena a rival to reckon with for any competing predator.
This illustration shows Pachycrocuta cracking a large ungulate bone, and a schematic view of the anatomical features involved in this action. The massive muscles of mastication (temporalis and masseter) provided the huge force necessary to crack the bone with the premolar teeth, and the domed forehead helped to dissipate the stresses generated during the bite
But, was P. brevirrostris a scavenger and a kleptoparasite of predators such as the sabertooths, or did it kill much of its own prey? This is a good question and one to which we may never get a final answer. On one hand, its skull and dentition were adapted to process bone at a phenomenal scale, so it was clearly very well adapted to scavenging. In fact, the cutting blade of its carnassial teeth was slightly shorter than in the highly predaceous modern spotted hyena, leaving more room for the crushing section of the dentition, a detail that suggests a more scavenging lifestyle.
On the other hand, the huge body mass of P. brevirrostris made it less efficient for this animal to forage through the enormous distances required in order to come across such a dispersed resource as carrion is. More purely scavenging species, such as the modern brown and striped hyenas, are much lighter, and actually weight considerably less than the more predatory spotted hyena. And while a large body mass can be a problem for long-distance foraging, it can be an advantage for active hunting, since one or several heavy hyenas can be more effective at subduing and bringing down a large prey animal.
Whether it killed or scavenged most of its food, the fact is that Pachycrocuta had the habit of bringing lots of it back to its den sites, a habit which apparently explains the origin of several remarkable fossil sites. If nothing else, paleontologists need to be grateful to this gigantic bone cracker for its efforts to collect hundreds of bones and gather them in the places where they eventually became preserved as fossils.
A family group of P. brevirrostris gather at the den site, where the cubs play with some old bones. Such dens, when placed near seasonal lakes or waterholes, could be buried by mud during floods and the bones would be preserved as fossils
El próximo 18 de Marzo, impartiré la charla titulada “Los grandes felinos de África: evolución, pasado y presente”. Desde mi primera visita a Botswana en 1993, mis viajes a África en busca de los grandes felinos han supuesto un contrapunto y un complemento a mi trabajo de investigación sobre la anatomía, evolución y adaptaciones de estos animales. Pero a lo largo de estos años también he tenido ocasión de estudiar en diversos museos los restos fósiles de los félidos extintos de ese continente. En esta charla hago un rápido repaso a la historia evolutiva de los félidos en África, mostrando algunas de las especies más sombrosas que allí han habitado, así como unos breves apuntes de mis observaciones más sorprendentes de los leones, leopardos y guepardos en su ambiente. Finalmente proyectaremos en primicia mi documental “Belleza Salvaje: la visión de un artista de los grandes felinos africanos”.
La conferencia será en el marco del Gabinete de Historia Natural, un espacio de encuentro para todos los aspectos de la naturaleza en el centro de Madrid.
Lugar: Calle Victoria, 9. Madrid.
Entrada: 5 Euros hasta completar aforo.
As we have seen in previous posts, the Miocene was a time of gigantic hyenas and hyena-like predators. But more than that, it was a time of hyaenid diversity. So, members of the hyaenid family occupied different ecological niches, and we talk of the “civet-like”, “mongoose-like” and the ”dog-like” hyaenas, besides the more familiar “bone crackers”.
Giant bone-crackers like Pachycrocuta, for instance, were no doubt spectacular animals, but my personal favorite are the dog-like hyenas. Comparable in build and body mass to today’s coyotes and wolves, these species combined their elegant, gracile skeletons with a “multipurpose” dentition that allowed them to take a variety of middle sized prey which they would consume to the last bone, but they also could search far and wide for any carcass in the landscape, scavenging both in an opportunistic and in a more determined way.
Years ago, during my visit to Hezheng in China I was fortunate to study first-hand an amazing sample of Hyaenictitherium fossils, including many postcranial bones that gave me a much clearer idea than I had before of the body proportions of these animals.
Finally, here is the reconstructed life appearance of Hyaenictitherium, an animal that would have the approximate size of a modern coyote. The coat pattern is broadly based on that of modern hyaenids, especially that of the striped hyena and the aardwolf, but some reference to viverrids is also made
Hyaenictitherium wongii and similar species somehow filled in the Old World the niches that the true dogs were occupying in North America at about the same time. With time, some lineages of dog-like hyaenids evolved into the “hunting hyenas” of the Pliocene, apparently the only hyaenids that eventually made it to the New World… but that is a different story!
During my visit to the amazing fossil sites and Paleontology Museum of Hezheng province in China I had the opportunity to study first-hand a whole range of beautiful carnivore fossils. Among the best preserved of them were several skulls of the Miocene hyenid Adcrocuta eximia. As I mentioned in a previous post, Adcrocuta took the place of the much larger “monster-hyena”, Dinocrocuta in the Baodean environments in China, broadly comparable in age to the Turolian of Europe.
Here is one of the admirably well preserved skulls of Adcrocuta on display at the Hezheng museum of Paleontology
Unlike Dinocrocuta, Adcrocuta was a true hyena, and its size and proportions look far more familiar to a modern observer. The Hezheng skulls define the shape of the animal´s head admirably well, and allowed me to prepare a series of quick sketches of its possible life appearance. These are just impressions, but to me they are enough to get a glimpse of Adcrocuta as a lively and efficient predator and scavenger. It was the inseparable rival of Amphimachairodus in all of Eurasia, from Spain to China, but for some reason, and unlike the sabertooth, it never made it to the New World. One of the many mysteries of hyenid evolution.
It was once a popular notion to see Miocene hyenas as mere scavengers depending for their livelihood on the kills of the sabertooths. But just as we now know that modern spotted hyenas are efficient predators as well as scavengers, so our view of their fossil relatives has become more complex. The fossil record is giving more insights about these animals, and about Adcrocuta in particular. We shall see more about t in future posts!
More than a decade ago I made a reconstruction of the head of Dinocrocuta for the book “Mammoths, sabertooths and Hominids”. Back then I had not seen a single postcranial bone of the animal, but its head was impressive enough to set it apart from any other carnivore.
The skull is enormous, and yet it seems to provide barely enough room for the outsized cheek teeth. And that visual impression is well founded: if we compare the tooth row of Dinocrocuta with that of a more “typical” carnivore, such as the wolf, we notice that the premolars have become huge and they have pushed the carnassial back, farther back than the orbit. In comparison, the carnassial of the wolf is actually ahead of the orbit. As the emphasis became so strong on the function of the premolars, the molars behind the carnassials (still well developed in the wolf) became reduced or eliminated, there was simply no room for them!
In comparison, the carnassials of the wolf, seen below, are in a much more anterior or rostral position, well ahead of the orbits, and unlike the case of Dinocrocuta, there are still several sizeable molars behind them.
The functional reason for these transformations in the dentition of Dinocrocuta is clear: just as in the true hyenas, the premolars are the bone-crushing teeth in these animals, and in order for them to exert the greatest force on the bitten object, they need to be as close as possible to the articulation between the skull and the mandible, so the whole premolar row is pushed back.
The result is a skull desing that parallels the features of bone-cracking hyenas, as has been confirmed by a Finite Element Analysis of CT Scans of the fossils (see the paper here: http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8312.2008.01095.x/abstract). But just like modern spotted hyenas the animal was also well prepared to take its own prey, thanks to its powerful canines and incisors. This is confirmed by evidence provided by one of the victims of this fearsome predator. Effectively, a skull of a Miocene rhino of the genus Chilotherium from China bears canine marks that fit nicely with the size and shape of the canines of Dinocrocuta, which also happens to be present in the same fossil site (see the paper here: http://link.springer.com/article/10.1007/s11434-010-3031-9#/page-1). The rhino, however, managed to escape that particular attack, and the bone shows evidence of healing; a rare example of an animal that got up close and personal with Dinocrocuta and managed to escape with its life!
Some 8 million years ago, the plains of central China were home to an incredible diversity of wildlife. Herds of antelopes, rhinos, three-toed horses and giraffe-relatives browsed and grazed in the open woodlands and prairies. The imposing sabertooth Amphimachairodus was very much in evidence and could hunt many of those herbivores, but it was not the uncontested ruling predator. There was one monstrous carnivore around that could easily displace the sabertooth from its rightful kills, a creature that we now call Dinocrocuta.
Dinocrocuta was a hyena-like predator, and the similarities made early scholars believe that it belonged in the same zoological family as modern hyenas. But more detailed studies have shown that it actually belonged in a related but separate family, the Percrocutidae, and the remarkable resemblance to modern hyenas is largely the result of convergent evolution. Like the true hyenas, percrocutids evolved adaptations for cracking bones, developing massive premolar teeth and a robust skull with a strikingly arched forehead. But Dinocrocuta took these adaptations to a truly massive scale. The largest living spotted hyenas can weight around 80 kilos, already imposing, but Dinocrocuta doubled and maybe even tripled that mass.
During a trip to China a few years ago I was privileged to study first-hand an incredible collection of Dinocrocuta fossils. It is impressive enough to see pictures of the skull of this animal, knowing that it measures about 40 centimeters in lenght. Seeing massive skull after skull in front of your eyes is a different thing. But seeing a partial skeleton just blows your mind.
Here is a picture of a skull of Dinocrocuta gigantea on exhibit at the Museum of Paleontology in Hezheng, China. This is just one of many such skulls housed in the museum’s collections
As a result of those observations I created a preliminary reconstruction of Dinocrocuta which, for the first time, brought it to life in my mind’s eye as a complete animal.
The resulting picture is that of a somewhat hyena-like animal, but the head is absolutely and relatively far more massive. The combination of a huge body mass, a massive dentition with powerful canines and crushing premolars, and a skeleton well adapted for efficient locomotion on land, meant that this animal could cover large distances in search of carrion, or of its own prey, and that it could evict any other predator from its kill -except, perhaps, another Dinocrocuta!.
In the faunas of the Hezheng basin, Dinocrocuta is the dominant large carnivore in the Bahean-aged sediments, broadly comparable to the Vallesian of Europe with an age estimate of between 11 and 7 million years. Afterwards, with the advent of the Baodean age, it becomes very rare or extinct, its place taken by the much smaller Adcrocuta, a true hyaenid very similar in size and adaptations to the modern spotted hyena. And then Amphimachairodus becomes a much more common fossil occurrence, probably reflecting in part its real dominance in the habitat. After all, dealing with the competiton of Adcrocuta would be more or less like dealing with spotted hyenas for a lion: largely a matter of numbers. But Dinocrocuta was a different matter; trying to stop it from stealing your kill would be like trying to stand in the way of a speeding freight train. And Amphimachairodus was probably wiser than taking such risks.
It is really hard to imagine why such an imposing creature would go extinct and leave its place to the much more modest Adcrocuta. As more fossils of Dinocrocuta are discovered we can expect to see detailed studies that will reveal more and more of its paleobiology, and hopefully we will come closer to understanding the mystery of its final demise.