Sunday, 14 March 2021

Miocene (Pt 25): The Large Clawed Cat-Cat and the First Dog in Africa

Today, the hyena family consists of just four species. All of them live in Africa and, generally speaking, they look somewhat like dogs. Three out of the four are scavengers, with powerful teeth adapted for cracking open bones to consume as much of a carcass as possible. The largest and fiercest of these is the spotted or "laughing" hyena, which is the one most people think of when the word "hyena" is mentioned, although there is more variety in the group than that. But even so, with just four species, it's not what you'd call a large taxonomic family.

During the Late Miocene, however, things were very different. It's hard to know the exact number of species that existed, even among the fossils we have, since some of the subtler differences may not be apparent from bones alone. But there were certainly plenty of genera, spread widely across Europe, Asia, and Africa. They were also more varied than today, and their success at the time may well have been due to the fact that actual dogs were still restricted to North America at the time, leaving the hyenas without direct competitors.

The oldest fossil dog in Africa is Riffaut's fox (Vulpes riffautae), an animal quite similar to the modern red fox that lived in Chad around 7 million years ago, in the second half of the Late Miocene. In fact, it's quite possibly the oldest fossil dog we know of anywhere outside of the Americas, although logically, it must have had ancestors somewhere in Eurasia that we haven't found yet. Its arrival may have heralded the end of hyena dominance, although that did take a few million years to play out.

At the time, hyenas were a moderately diverse family, with at least three different body plans. The original hyenas hadn't looked much like dogs at all, instead betraying their evolutionary relationship with civets and mongoose, but these were in decline by the Late Miocene. The other two forms were both much more dog-like. One consisted of fast-running pursuit predators, such as Chasmaporthetes, which is better known from Asia but had at least one species living from central to southern Africa.

More widespread were the third type; hyenas with a jackal-like appearance, and that likely had a similar lifestyle to those animals. The best-known of these from Africa is Ictitherium ebu, a long-legged and slender animal with less of a sloping back than modern hyenas have. The shape of its teeth suggests that it was more carnivorous than its omnivorous relatives elsewhere (and, indeed, it has been questioned how closely related it really is) but certainly it was quite different to the living species of the family. Hyaenictitherium minimus is another example, apparently common in central Africa, although how closely related the two are to each other, or to their supposed Eurasian relatives, is disputed.

At around this time, however, we do begin to see the appearance of a fourth type of hyena, those adapted to bone-cracking in the same way as the modern species are. Whether this really first began in Africa is debatable, but one of the earlier hyenas that clearly does have teeth adapted to crunching up bone (although not to the extent that the living hyenas do) is Belbus which, although it is also known from Greece, has also been discovered in Chad.

Whether or not they ate bone, many of these early hyenas were likely scavengers on carcasses of animals killed by larger predators, at least some of the time. And there were certainly a number of larger predators to pick from. 

Among the most obvious would be the sabretooth cats, which had already been present in Africa for some time. By the Late Miocene, several species of sabretooth lived on the continent, most of which were immigrants from the north, and better known from the more extensively studied fossil sites in Europe and Asia. Amphimachairodus is the clearest example of these, with most its fossils actually having been found right the way around the world in North America. (This might sound rather too far for a single genus... but consider the existence of both leopards and jaguars today). Others are often less easily assigned; something akin to Dinofelis may have lived in Late Miocene Africa, but the remains are too fragmentary to be sure exactly what it was.

Two kinds of sabretooth are, however, unique to the continent, at least so far as we know. Tchadailurus was described in 2018, and was an unusually primitive sabretooth for something living so late. It was about the size of a lynx and must have diverged from other sabretooths very early on since it lacks many of the features we'd normally expect in such animals; a member of the group almost certainly, but not very terrifying as such things go.

Lokotunjailurus was a rather different matter. This was about the size of an adult lioness, although rather more slender, so it may not have been a huge animal... but it was certainly large enough, for a predator. Originally discovered in deposits in Kenya, it, too, formed part of the fauna in Chad. In the latter case, the fossils were found along the shore of an old lake, but that probably says little about the habitat of the animal, since it's the sort of place that bones are likely to end up and become buried in mud, and it probably spent a lot of time in the savannah further away.

The fossils in Kenya, however, were rather better preserved, due to being entombed in particularly hard rock. Which, obviously, made it very difficult to get them out, but had also kept them relatively intact during the 8 million years or so since the animal had died. The relatively complete nature of the skeleton was most notable for allowing a detailed examination of the creature's paws. (In fact, the full scientific name translates as "clawed cat-cat" in Greek and Turkana). These showed that it had enormous dewclaws, larger than those of a fully-grown male lion, despite its other claws being unusually small for the animal's size. These would surely have been clearly visible when it was alive, and were doubtless used to rip open the body of the creatures it had overpowered.

Sabretooths were not, however, the only large mammalian carnivores in Africa during the Late Miocene. Bears are not found in Africa today, but at least some, such as Agriotherium, reached the northern parts of the continent in that distant time, giving rise to at least one species local to South Africa in the following, Pliocene, epoch. The bear-dogs, which had been quite common earlier in the Miocene, were dying out, as they were elsewhere in the world. It may, however, be in Africa that they held on for the longest, with the last known example being Bonisicyon. With a more heavily meat-based diet than many of its ancestors, this was also unusually small, about the size of a coyote, and it died out 5 million years ago, just as the Miocene ended.

Other examples belong to groups that we don't associate with large predators today. Mustelids, members of the weasel family, were widespread in Africa at the time, including otters and early honey badgers such as Erokomellivora. The largest, however, was Ekorus, which has been estimated to weigh anything from 40 to 48 kg (90 to 105 lbs), somewhat larger than the average wolf. The legs are also much longer than we'd expect for a mustelid, and are perhaps closest to those of a leopard, suggesting that it may have hunted in a similar fashion. 

While it probably looked something like a giant, long-legged wolverine, exactly where it fits in the mustelid family tree has been difficult to assess. Some of the skeletal features are similar to those of the modern honey badger, so that is often cited as a relative. On the other hand, honey badgers are specialised for digging, which Ekorus clearly wasn't, so, if it belonged that that lineage at all, it was probably quite an early branch.

The giant civet (Viverra leakeyi) was about the size of a jackal, considerably larger than its modern relatives. The shape of the teeth suggests that it, too, was an active predator with a considerable amount of meat in its diet, whereas modern civets are omnivorous and only around half the size. In other respects, its most closely resembles the living civets of India, rather than those found in Africa today. Whether that's a genuine reflection of its ancestry is far from clear, and there's also some doubt as to whether the Late Miocene examples are really the same creature as that which produced the more numerous Pliocene fossils.

I've already described many of the herbivores that these predators and scavengers would have been preying on. But there is at least one group of potential prey animals found in Miocene Africa that I've passed on up until this point, and they're far from insignificant. So that's where I'm going to look next...

[Picture by Mauricio Antón, available under the terms of CC-BY-3.0 NL].


  1. The fourth modern hyena is, of course, the myrmecophagous aardwolf. Are there fossil hyaenids with similar habits known?

    1. I suppose there's Proteles transvaalensis, which is a Late Pliocene member of the living genus, and possibly some Pleistocene aardwolves, but otherwise, nothing that I'm aware of.