These Primates Don't Look Like Primates. How to Fix Them

Question

For years, I've been building and rebuilding an alternate Earth. The point of departure is 56 million years ago, when the hottest episode in the last 100 million years, the Paleocene-Eocene Thermal Maximum, lasted four to five times longer than it did in our timeline. Here is some of the backstory that is relevant to the question at hand, with some passages highlit in bold:

The evolutionary history of the primates, like virtually everyone else's, is long and extremely confusing. According to the molecular clock, the last common ancestor of all primates lived between 90 and 63 million years ago, yet we have found no fossils dating from that particular window. Apparently, the dry-nosed haplorhines (tarsiers, monkeys and apes) came first, with the wet-nosed strepsirrhines (lemurs, bushbabies and lorises) diverging from the haplorhines between 90 and 55 million years ago. There is conjecture that Plesiadapiformes were archaic primates, but there is doubt as to whether modern primates actually evolved from them. Two other groups, Adapiformes and Omomyoidea, throw a monkey wrench at the case because both groups appeared suddenly in the fossil record with no physical evidence of past transitions, and they were already diverse by the Eocene. So were those two groups already around to witness the Paleocene-Eocene Thermal Maximum, much less the fall of the dinosaur empire one million decades earlier?

Well, whatever the case, at 1750 species, the primates ended up being the most diverse of Great Lakes Earth's mammals, occupying the niches filled back home not only by our primates, but also by fruit-eating and predatory bats, sciuromorph rodents, carnivorans and even cetaceans.

The two superfamilies of carnivoran-like primates, the feliform-like terrailuroids and the caniform-like mixotherioids, have been identified as adapiform primates, which is amazing because back home, that particular group died out during the Miocene.

Here are some of those "carnivoran-like primates", all drawn from a commission by the DeviantArtist "AlienOffspring".

The dobarchu--an adapiform primate that looks like a cat that lives like an otter--and the dard, an adapiform primate that looks like a cat that lives like a badger.

The onza, a primate in a world sans Puma, and the pard, a primate in a world sans leopards and jaguars.

Two species of sphinxes, plains-running pursuit predatory primates in a world sans lions, cheetahs and scimitar-toothed cats.

A Bengal tiger used as a comparison for the two species of dubas, forest-exclusive primates that wrestle its prey like saber-toothed cats did in our timeline.

The lingbacker, an Arctic/Atlantic primate in a world sans rorqual whales.

The criticism here is that none of them look even remotely like primates, so what changes would be needed to better sell the audience that these are, indeed, primates in an alternate Earth?

Answer 1

I'd recommend focusing on the traits shared by the largest subset of primates.

Five fingers and opposable thumbs

There's only three primate species without five fingers, and even their hands have four. The presence of a hand is a very recognizable primate trait.

Fingernails

Likewise, almost all primates have flat nails on their fingers, rather than claws. The primates that do have claws, have grooming claws on their hind legs — not footpads with claws, like your pards, sphinxes, and so on.

Flatter faces / no snout

One of the key features of primates is sacrificing smell for vision. All diurnal primates are at least dichromatic. Having a snout breaks up the 'face' dynamic that we associate with primates

Forward-facing round eyes

Paired, forward-facing round eyes with no major obstruction. Having pupils, retinas, and sclera. Aping that will help create the primate-esque gaze. Even tarsiers, the usual exception to every rule for primates, have these

Answer 2

Start with a primate, then work towards your creature.

https://sibyliachavonet.artstation.com/projects/DPeyG

Your creatures look a lot more like their real world nonprimate analogs than they do like primates. I take it that is your problem. I suspect your artist started with a familiar animal, then tweaked it.

A solution would be to have the artist start with a primate as the model, rather than the real world analog animal. Your badger and tiger as drawn look like a badger and a tiger. You could make them more plausible primates by starting with a baboon and a gorilla. Keep hints of their provenance. Your audience will see the long nose and ruff of a baboon, see the tail and stance and understand that this thing is fundamentally a baboon. Your audience will see the distinctive humanoid musculature of the gorilla transferred on a catlike frame and understand that this is a gorilla that has gone tiger.

Answer 3

Exercise your creativity

Primates are rather primitive mammals; some of the Haramiyida, if encountered, might plausibly be thought to be primates, at least at a distance, and they likely precede mammals entirely. So there is conceptually not much problem with imagining that primates could have branched out and become cats and whales and so on, if circumstances encouraged it. After all, there's literally no telling what evolution could have done.

Nonetheless, a neo-whale isn't going to look like a primate, any more than you can have your cake and eat it too. If you want a primate that lives under the water and eats plankton, you want some kind of Kurt Vonnegut solution. (I didn't find useful art; This isn't it, but dang...) Maybe your primate whales build some kind of combs that catch plankton, and catch it in a toothy maw that looks more like a mutant vampire horror. Perhaps they use prehensile tails to latch onto whale sharks and force them to do the swimming. Maybe the sphinxes are more like chimpanzees in how they prey on and tear apart other primates; maybe they can navigate the forest canopy whenever it suits them. To make primate-looking creatures, you need new life histories different from those best suited to existing non-primates.