WWB Redux: Dinofelis aronoki

"At first glance, you might think you were in the 21st century but there are important differences. The big cats are actually of the saber-toothed variety, although these ones only have small sabers."

Dinofelis, a group of mid-sized to big cats that are remarkable for just how...unremarkable they are. So unremarkable in fact, that workers have been debating about where exactly their tribe, the metailurins, fit within the Felidae family, whether they are true machairodontines or perhaps closer to panthers, with their large-but-not-terribly-large canines being conical rather than more flattened and blade-like like in smilodontins and homotherins. This confusion is even reflected in the WW series, with "Next of Kin" identifying Dinofelis as a saber-toothed cat while Walking with Caveman calls it a "false sabretooth". Currently, they are considered machairodontines, even if rather conservative and basal in their morphology, though that might change again with future studies and discoveries. Metailurins first emerged during the Late Miocene (when cats, specifically machairodontines, first became apex predators across the globe), with the best known one being the type genus, Metailurus and the new genus that split off from it, Yoshi. Dinofelis was the last of the metailurins, the only one to survive into the Pliocene. While the earlier taxa were more lithe and longer-legged, Dinofelis was stockier in build, more like a jaguar than a pseudo-cheetah.

Though evidently not as successful out of Africa as its two contemporaries, Dinofelis formed a machairodont trinity with the larger, cursorial Homotherium and the basal smilodontin Megantereon, with the three being apex predators across the Old World during the Pliocene epoch, and all three migrated into North America, though again, Dinofelis doesn't seem to have been particularly successful there either (with only one specimen known from Texas). The narration in the opening of "Next of Kins" notes how one big difference between present day and Pliocene Africa is that the top cats on the savannah are sabretooths, which is correct, as panthers at the time were still unassuming, basal critters most similar to leopards, like Panthera shawi, and fossils of them are rare and fragmentary in Pliocene Africa, since they likely originated in Asia during the Miocene-Pliocene turnover (with taxa like Palaeopanthera and Pachypanthera being the oldest). But once the Pliocene gave way to the Pleistocene (and the start of the ice ages), panthers start to become more common in Africa, with lions and leopards (the leonine panther lineage) coming onto the scene around 2 mya, while sabretooths gradually decreased in prominence in the Old World, with Dinofelis, Megantereon and Homotherium all vanishing from Africa by the upper Early Pleistocene (circa 1.8-1.5 mya), perhaps partially due to increased competition from lions and leopards, though Homotherium at least had no trouble coexisting with the leonines on the Eurasian mammoth steppe up to at least 30,000 years ago (though fossils of it from Late Pleistocene Eurasia are rare), and possibly climate change too, with Africa continuing to become more arid and dominated by open savannah.

The name Dinofelis originated in 1924 for the proposed Chinese species Dinofelis abeli, but the type species, Dinofelis cristata was named back in 1836, as a species of Felis (which once included all extant felids but is now restricted to the domestic cat and its nearest relatives), and the latter's type material comes from the Sivalik Hills of India, and it's noted for resembling pantherines, and was thus later named Panthera cristata. D. abeli might be synonymous with it, meaning both the generic name Dinofelis and the type species of the genus originate from Asia, despite the genus being chiefly known from Africa. Other material attributed to Dinofelis has also been attributed to panthers, like the holotype of the sole North American species Dinofelis paleoonca, known from a skull and jaw from Texas's Blanco Formation, which was initially thought to be a jaguar-like pantherine. Again, this highlight how generic Dinofelis is compared to many other large felids, with certain species leaning more heavily on being panther mimic (like "Panthera paleoonca"). While the odd fossil has been recovered from North America, southern Asia and Eastern Europe (like Moldovia), most of the known material comes from Africa, namely East Africa and South Africa (like the Swartkrans cave), and many different species have been erected and synonymized over the years. There was one study in 2001 (when WWB aired) that sought to revise the genus and found around 8 valid species, but I can't find any online copies of it, and it's over two decades old. These species varied in size, from the size of a snow leopard up to the size of a large jaguar. The last known species, the South African Dinofelis piveteaui, lived during the Early Pleistocene and it too has been noted for sharing morphological features with panthers. By contrast, Megantereon (with M. inexpectatus) managed to find one last stronghold in East Asia well into the Middle Pleistocene (some 500,000 years ago), and Homotherium continued to do well further north on the mammoth steppe thanks to its cursorial adaptations making it an ideal open plains hunter (though evidently not in Africa?) Again, Dinofelis just kind of falls behind.

Like the "cave lion" in "Mammoth Journey", the Dinofelis is obviously modified from the Smilodon model, being given a long tail like the "lion" but its face has also been altered and foreshortened. Overall, in this case, the modifications make the design a decent one for Dinofelis, which was rather generic in its morphology to begin with, though like with many other of the mammals in WWB, it certainly suffers a bit form the primitive CGI, not looking quite cat-like enough, especially with the thin, bony tail and like Smilodon, it has those weird, tiny ears, and just like the Hyaenodon, there's some rostral shrinkwrapping going on, since its small sabers would have been tucked behind its lips (line in most non-smilodontin machairodontines), thus making it look even more like a generic big cat. Much like how the Smilodon's behavior in "Sabretooth" is copied and pasted from African lions, the Dinofelis very much acts like a leopard, to complement the Australopithecus's chimpanzee. They even have it sleep in a tree with one of its front limbs dangling, in case it wasn't obvious. Unlike the Smilodon, this at least makes more sense, though Dinofelis wasn't exactly a leopard mimic, being stockier and (at least in some species) notably larger, so it might have acted more like a jaguar (though that doesn't mean it loved taking baths and hunting crocodiles). Similarly, this makes it less likely that Dinofelis, especially the larger forms, stashed their kills in trees like leopards, given that they were one of the largest African cats around 3 million years ago, though it's not impossible either, with packs of Xenocyon (large-sized lupines) and clans of Pachycrocuta (lioness-sized bone-crushing hyenas) running around in the same biome, though that also hinges on Dinofelis being solitary, and not more gregarious as both Smilodon and Homotherium have been speculated to have been based on circumstantial evidence, and I guess packs of Homotherium could have been another potential threat.

One misconception about WWB's Dinofelis is that it's depicted as a hominid specialist and that the real deal didn't actually hunt primates. Again, I have to correct the ignorant. For one, the narration never actually claims that it's a specialist hominid hunter, it just says that it's a "killer of Australopithecus" and a bulky ambush predator not well suited for hunting fast-running herbivores (in the novelization, we see an Ancylotherium that was killed by a Dinofelis, instead of a zebra). Now, as for why they went with Dinofelis as the antagonist of the episode instead of Megantereon (who would have just needed to be a color-swap of the Smilodon, with no tweaks), it's likely tied to one of the episode's consultants. Charles "Bob" Brain (now that's a scientist's name if I ever heard one) is renowned for his work at the Swartkrans caves, where we find abundant fossil material of monkeys such as baboon and human-line hominids; Paranthropus and (less commonly) archaic Homo species, especially skulls, dating to the Early Pleistocene (around 2 mya). During the 70s and 80s, Brain dispelled the antiquated and rather silly ideas about the ape-man beheading each other and stashing their enemy's severed heads in the cave (which frankly sound like something out of an old, pulp fiction caveman comic) and showed that these fossils were stashed here by carnivorans hunting our predecessors (even writing a book about it in 1981 titled "Hunter or Hunted?"), and cited Dinofelis as a likely culprit, especially with the scalp of a young Paranthropus showing twin holes that were left there by the lower canines of a big cat as it dragged it away. Whether that cat was a Dinofelis, an early leopard, or Megantereon, we can't really say, since any species will display individual variation, like in size or subtle differences in morphology, so the spacing between tooth marks isn't much of a clue.

But then in 2000 (when WWB was in production), an isotope study on the predators of the Swartkrans region found that leopards, Megantereon and the running hyena Chasmaporthetes habitually consumed primates while the local Dinofelis favored grazing animals. However, this is just one small region of Africa (a continent of 11.7 million square miles), and all these predators including the multiple species of Dinofelis lived all over Africa, and "Next of Kin" takes place much further north in the Hadar region of Ethiopia. And big cats, like most predators, aren't picky, they will hunt whatever is most available in any given region, and their dietary preferences will vary depending on which animals are the optimal prey choices in a specific locality, not to mention that they will also readily exercise opportunism whenever possible. And human-line hominids represent soft, gracile, slow-moving targets with few defenses, especially before they started toying with spears and fire, and even today, people in Africa are not off the menu for big cats and get dragged out of their homes to be eaten. So yes, what's shown in "Next of Kin" is perfectly plausible, especially with it being an individual Dinofelis that menaces the clan, akin to how certain leopards in Africa's rainforest may become serial chimpanzee killers, and chimps are far more dangerous than a lightweight, fangless Australopithecus.