#pachybara

[alphynix]

Transcript for the text on the image under the cut:

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Spectember 2020 #08 | nixillustration.com | alphynix.tumblr.com Concept suggested by: anonymous

Giant Cavy-Ungulates

(Rodungulata)

The present-day Patagonian mara (Dolichotis patagonum) is a long-legged caviid with almost hoof-like digits on its feet, somewhat resembling a rabbit-deer. These unusual rodents are diurnal fast-running grazers, already rather convergent with ungulates – and so it's perhaps not too surprising that eventually this lineage produced the RODUNGULATES.

[Image: a modern mara, an animal that looks rather like a rabbit-headed deer.] The ancestral Dolichotis patagonum

Starting out as relatively small animals similar to early horses, rodungulates quickly increased in body size thanks to some of the physiological quirks of their ancestors. Along with both their chisel-like incisors and grinding molars being ever-growing, they were hindgut fermenters specializing in eating very high-fiber diets of tough vegetation – including plants toxic to most ruminants – and breaking it all down in their large intestines. While less efficient than ruminant digestion this system allowed them to feed in bulk and process their food much more rapidly, which at larger body sizes became a significant advantage.

So, much like the proboscideans and indricotheres before them, some of the rodungulates were able to become especially big mammals.

Reaching at least 3m tall at the shoulder (9′10″), the giant rodungulates range from heavily-built rhino-like forms to slender long-necked high browsers and tapir-like low-level browsers. Most of the largest species are ecosystem engineers similar to elephants, stripping bark, clearing trees, fertilizing soil, and creating areas of open grassland where other species can flourish in their wake.

[Image: a descendant of the mara that looks like a small horse or deer, with four hoof-like toes on its front feet and three on the back.] Cavihippus velox, a basal rodungulate convergent with early horses

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[Image: a heavily-built rodungulate that resembles a capybara with a rhino-like body. It has a thick bony dome on its forehead.] Pachybara tholussa, a rhino-like rodungulate. The “dome” of thickened bone on its head is used for flank-butting.

[Image: a long-snouted rodungulate with a body plan somewhere between a camel and an indricothere, with long slender legs, a long neck, and a sloping back.] Caviauchenia longinaris, a high-browsing rodungulate. Similar in body size to giraffes and mid-sized indricotheres, it uses a combination of a long neck and an unusually long snout to reach more vegetation.

[Image: a chunky vaguely tapir-like rodungulate with a tall blunt snout somewhat reminiscent of a moose or a ground sloth.] The slightly smaller Theriosonax altirhinus is more specialized for browsing, with a semi-prehensile upper lip. Its large nose acts as a resonating chamber for loud calls.

[Image: a different view of Theriosonax's head with its mouth open, showing its large chisel-like incisor teeth.] Like all rodungulates, its rodent ancestry is most obvious from its chisel-like incisor teeth.

[speculative-evolution]

SOURCE

This particular piece was for the Weldon Owen encyclopaedia but looking at what might end up as fossils. As such, I was asked to imagine an evolutionary record for the future. For this, I enlisted the help of palaeontologist and friend, Darren Naish, who gave me various ideas on those animals that might outlast humans. These include: The combat chick or chicken runner if you will: with the destruction of most ground-based herbivores, the superbly generalist chicken steps up to fill the void. They have re-evolved wing claws and the spur cocks used to fight has developed into a raptor-like sickle claw. It still retains the comb of its domestic ancestor. The pachybara: a pachydermal capybara. Not necessarily a direct descendent of the capybara - just a very large rodent. I did take the capybara as the role model. For instance, the big gland on its head has developed into a large horny boss. In my future, it has stepped up to fill in the niche of the elephant and rhino. I also gave it couple of extended tuck-like incisors for stripping bark. The pachybaras aren't the large sort of pachyderms we know and love; the low-energy ecosystem I had in mind wouldn't probably support animals that big unless they had very slow metabolisms. The rats: This is the one I've given most thought to. Darren mentioned the miniaturisation and socialisation of the naked mole rat, so I decided to take that and run with it. Now the mole rats are far smaller but more social and have developed vast underground kingdoms like termites. As an exploitable resource, they have their hunters, in this case a highly derived rat that has evolved along the lines of the anteater, pangolin and porcupine. I took the spiny rats of South-East Asia as an example, but because it has had to leave the safety of the shadows to hunt mole rats, its spines have become full-on prickles. It has huge forearms and claws to dig down into the mole rats' burrows then uses an extended snout and a sticky tongue to capture the squirming pink mole rats. It's not very clear from the picture but I like the idea of extended chiselling incisors for digging - rodent teeth are after all continually growing and it wouldn't have to worry about wear. The mole rats, meanwhile, are fighting back. They have developed a soldier caste like termites - I drew one out in the foreground, with big sharp pointy fangs. I see it as a miniaturised bulldog that swarm to the surface to attack anyone trying to break into the burrow. Another organism that has developed alongside the spiny rat is the finch, again inspired by Darren's comments. In my future, they have evolved alongside the rats. Like some of Darwin's finches, they have also developed tool skills, but instead of using sticks to impale termites, they follow the big rat in and spear up any mole rats. The spear, sometimes twigs, sometimes discarded rat quills, also act as a stand-off weapon, keeping them away from the soldier mole rats. They are also used to drive off cane toads (asked for by the publishers), which have become another spiny rat acolyte; the toad uses its big sticky tongues to swipe up mole rats blithering around after the rat has dug them out from their nest. Tool-using finches have been selected against the more idiotic birds that ended up poisoning themselves on the toad's huge toxic glands. On this occasion, the toad is raised up on its legs and ballooning up to try and scare off the finches prodding it with their sharp implements. Behind them, out on the drying flats, a panzer croc ('velocisuchian') is pulling down a chicken runner hen whilst the cock springs to her aid, spurs flashing. The panzer croc is based on the Eocene running crocodile, Pristocampus, and I again used the low-energy Australasian environments as a model with the top carnivore slots filled by reptiles.