Are there any major problems with my creature design?

Question

This mammal-thing is based off of kangaroos, red squirrels, dromeosaurs, cats, and of course, humans.

My creature is slightly bigger than most humans, digitigrade and bipedal. It has a long, thick tail to help it balance when standing (Though it can stand without it, it's just harder.) and running. It can run on four legs without much difficulty, though it is not nearly as efficient as a true quadruped. When running on two legs its posture is much like a raptors.

Its head is wedge-shaped, and in it houses a smaller brain than a human, but it is just as intelligent. It has forward-facing eyes to match its cat-like pupils. These creatures have light, mostly hollow and blood-filled horns that are used for display. The more long and elaborate the horns, the more attractive. (This particular specimen is a sorry fellow.) It has a longer neck and torso than a human, but not by much.

Its arms are much longer though with its hands nearly reaching its knees. On these hands are pads and claws. Its feet resemble hands, but it is only about as dexterous as a human's foot.

EDIT: I am so incredibly sorry, I forgot to mention that it evolved from climbing ancestors. Not necessarily arboreal, but a similar environment. These creatures used to dwell in cave systems with complex rock formations that could be compared to a forest, but they were forced out due to a lack of food. It was a rather long time ago in their evolution, but that's why I gave them their horizontal shoulders. However! I adore the concepts given, so I may still change them up yet for a more unique, less human look.

Answer 1

if anything, the posture while walking, the flexibility of the tail and whether it has buttcheeks.

The main reason I started considering this is because you said the tail is important for their running and because of how you described their bipedal style of running:

When running on two legs its posture is much like a raptors.

And since I can't help but see a few similarities in terms of proportions, let's pull up a dead guy that seems pretty similar to your animal in a few regards: Dakotaraptor.

This image can show well 2 main traits of these dinosaurs: long legs with a shinbone region (the part of your leg that includes the tibia and fibula, making part of the lower leg) was longer than the thigh bones by about 22% (which I'm only mentioning to say your creature might actually be pretty speedy depending on how a few things below the skin work), and something that is present in many dromeosaurids (or raptors, as we know them): a tail very adapted for running, that serves as a counterbalance to the animal and had most of its flexibility at its base, with an association of bony extensions (present in picture) and tendons (not present, unfortunately), ensuring that the rest of the tail was more rigid, potentially to quickly adjust their balance while running.

So why did I go through all that? Well, if your creature does run often like a velociraptor or like other dromeosaurids, it means their bodies will normally be almost horizontal to the ground, meaning that, since their quadrupedal gait is awkward, the tail is most likely one of the most important things to ensure their balance, which means it needs to be heavy and, if we are to follow the example of earth animals, it might be better off being rather stiff as it reaches the end, to better use it as a counterbalance.

Second thing is that, if the tail needs to be heavy to act as a proper counterbalance, their posture might have to be a little less upright, at least while walking around. If you want a better idea of what I mean, this dinosauroid drawn by Monopteryx might help:

Essentially, they might walk a little hunched so that the tail doesn't make them tip towards falling backwards.

The last thing really depends on their skeletal structure and muscle attachment points, but going over one last trait in theropods compared to modern animals: human buttcheeks exist due to fat reserves and large muscles attaching to the back of the pelvis. Meanwhile, it seems like some theropods, including T-rex, dromeosaurids and carnotaurus, had leg muscles attaching to their tails, with the muscle being known as the caudofemoralis, which attached to the animal's thighs.

So essentially, depending on how important running was for your creature or its ancestors, they might have a special tail with a flexible base and a stiffer end, they'll probably walk slightly hunched to make up for the tail's weight and function as counterbalance and their legs might actually have muscles attaching to their tails, which can change their appearance regarding the hip region.

EDIT: regarding the "cave update": This is actually quite the twist, because you said that they originally were adapted to life in a cave system that was structurally similar to a forest, but potentially allowing for more solid "branches" that supported more weight, which would explain why they'd have developed scansorial adaptations (that is, adaptations that aid in climbing such as powerful claws, opposable digits and prehensile tails). One very important thing about this however is that they weren't in a forest climbing trees, they lived within a peculiar system of caves, and only left this habitat due to a lack of food. This does help explaining some things, but also opens up a few factors we'd better look at to determine why your creature most likely went from cave dwelling climber to a more cursorial creature. Firstly, why is a forest-like cave a bigger deal than it seems? Well, because being adapted to living in caves without leaving means things work a bit differently than they would in other environments.

With that clarified, here's my little theory on how your creatures could have evolved from scansorial creatures to cursorial ones and why exactly your current drawing would actually represent an older member of the species:

Your creatures, since you stated lived most of their lives in the cave without leaving, were most likely smaller trogophiles (creatures that live mostly within the cave, but can still survive outside of it, unlike troglobites) that were well adapted to a life of climbing, using their claws And opposable digits to traverse the forest of rocks, with their Tails being used to aid in balance and compensate for the climbing angle, much like how we'd see in a leopard. As they were fairly small in size and adapted to living in the dark, their pupils were slit-shaped to aid in determining distance and for properly filtering light in eventual visits to the outside world, as well as for hunting near the cave entrance during the day. At their original size, they functioned mostly as agile ambush hunters that fed mostly on arthropods and bats (or rather the counterparts of such creatures) that they managed to catch. At this period, due to the lack of vines or other structures, they'd grow horns much lke deer during mating season in order to advertise themselves. Said horns however, would fall not long after, as they still hindered proper maneuvering (this is merely a suggestion, I'd say it's a little better and safer than having large blood-filled horns year round, now that I've put some more thought to it).

As time went by however, the appearance of new, more agile predators, these primordial creatures saw themselves being slowly outcompeted, resulting in a situation in which bigger members of the species were selected, as they could hunter bigger game that the new predators weren't as good at feeding on and thus had access to more food, being healthier than their smaller counterparts and slowly shift the point of selection from simply males with larger horns to bigger males overall, with those with smaller horns being more capable of dedicating resources to their own growth, resulting in a beginning of their reduction.

However, one of the problems that came with the increasing size of these creatures was that they could no longer find enough food within the cave, resulting in more frequent visits to the outside world until a point when they left the caves completely.

During this adaptation period though, they had to undergo a new problem: the outside world, similar to a Savanah biome in several ways, had a lot less trees and other structures to climb on, which were fairly fair apart from one another. At this period, they started differentiating between 2 main groups: the stubborn ones, which tried to simply insist on their hunting strategy and ambush prey from the trees (which is one of the theories on how thylacoleo a marsupial predator that descended from climbing ancestors, hunted its prey), and the cruisers, which adapted to be generalists capable of eating a larger number of foods, including plant matter and smaller animals, while also relying more on stronger legs to travel long distances and escape predators (much like modern ostriches). While the former group ended up once again outcompeted, this time both by pre-existing predators and because of the small number of ambush points they could use, the latter developed just fine. Their arms became slightly shorter, but retained their ability to grasp and claws to hold onto small prey and for more desperate attacks against predators and their spine suffered some slight alterations to fit a more bipedal stance, but the biggest changes happened to their legs and tail:

The tail, once smaller in proportion and useful in compensating for the angle while climbing, became longer, bulkier and much more rigid, with most of the flexibility concentrating at the base. Their hind limbs became much more foot-like, with their toes shortening in length until they'd almost lost 3 out of the 5, with the 3 outer toes becoming either highly vestigial or straight up gone, while the "thumb" and 2nd remaining toes were adapted for running, having fairly durable and sharp claws that dug into the ground and aided in traction. The leg muscles also began to become more concentrated near the hip region, with an association of tendons in the lower part of the limb allowing for more efficient running and walking at the cost of flexibility.

At the end of the process we'd have human sized mammal-things with legs similar in structure to a cross between an ostrich, a cheetah and a raptor, and a tail mostly similar to a raptor's. The hefty cursorial adaptations allows them to be very efficient walkers and speedy runners despite still not being the fastest around, but it essentially came at the cost of them loosing almost completely their ability to climb pretty much anything. Their generalist diet of plant matter and small animals means they don't need to worry about endangering themselves hunting bigger prey or being outcompeted by ambush predators.

Comparing these to your drawing, they'd have thicker legs, a more "rod-like" tail that mostly stays upwards and a little less fur. They'd also have less toes and a hind leg structure more similar to an ostrich or dakotaraptor's, with the exception This situation could still allow them to keep their "horns", but I'd still advise to have them work similarly to deer antlers and fall off once the mating period is done (so they don't have to carry a pointless weigh with little to no use in defense, since their main defense strategy is laying low and running away). Much like a secretary bird, they'd hunt smaller animals by using their height to see above the tall grass, using their powerful legs to stun prey with a kick and use their arms and Jaws to finish the job. Much like thylacoleo, the smaller brancase could also result in your creature having a fairly stronger bite that what would be expected for an animal with its size.

Answer 2

Your design isn't bad, but if your going for a terrestrial/cursorial design this could use some work. But for an arboreal form this is dandy. As john stated prior, the shoulders and hands are much more suited for a tree dwelling lifestyle as are the feet. Fewer and more rigid toes works much better for terrestrial locomotion than many and flexy(I know you said they are are useful as a human foot, but the artwork doesn't read as such.) That being said I would probably try to center the mass of the body a bit more. Art peice by Haanpere on Twitter. They have some uncanny valley creations, but these ones are very good and are in a good place in terms of a believable cursorial-saltatorial design that is also anthropomorphic/outwardly sapient. However keeping the head non-human is always a better move.

This is an image I did for a client not too long ago. But it might help. Here we have a saurian build, but pitched upwards. The tail is much thicker and I kept the reptilian musculature of the legs and pelvis. Humans are kind of a bad reference for a running/cursorial body plan as we are very slow compared to most animals and have bad joints and bones for the job. I ALWAYS recommend looking at other animals that do the job better and then just anthropomorphize or adapt the traits for your more niche needs.

Other than that your design aint far off the mark. One mistake I see people make when creating sophonts or other is that they think it has be upright, have human-like hands/arms, etc. that isn't the case, hell they don't necessarily even need to be carnivores, although it does help. I have created a lot of "aliens" not one of which would look be able to use a car, let alone wear human clothing. It is a good excersise to create things that make development of a material culture much more interesting as well as posing. And I am not saying you did anything of the sort, we all have different proclivities, I just get asked by other artists, clients or budding creature designers how do these sorts of things and we often have a very "human" way at looking at the problem and don't step out in fear of unfamiliar territory.

Answer 3

I second what both individuals already said. The tail as it exist now doesn't make sense. I won't repeat what was already stated by others in this regard.

Instead I'll nitpick about everything else! Though before I go out of my way to criticize everything let me say that most of it isn't that big a deal. That is to say that while I don't think this creature would actual evolve as described I think authors get a certain amount of artistic license and frankly having to limit yourself to only what should evolve can make rather boring species. if you fixed the tail thing, and possible the feet, I couldn't see myself even at my most finicky really being upset about the other details occurring in a story. Still you asked sooo....

Grasping feet sure are Handy:

The detail that most stuck out to me a odd, other then the tail, was the feet which you described as 'hand like' but being no more dexterous then a foot. I don't think this makes sense, either the hand is still serving as 'a hand', being used to grasp things like tree trunks and/or cave walls, or it will evolve into a more appropriate foot.

The reason for this is simple, ignoring my horrible pun it is useful to have a foot that can grasp things! Useful enough that evolution doesn't want to 'give up' that ability lightly. There is no reason to still have a hand-like foot and give up on the usefulness of dexterity, there must be something gained by sacrificing the ability to better grip.

By comparison let's look at humans. We evolved from arboreal creatures and when we split off from chimps/bonobos we likely did have grasping feet similar to what those animals had. So why aren't our feet useful for grasping now? because we sacrificed that to be better at walking! Our feet slowly adjusted to a more foot-like posture to support walking more efficiently. In this case we did give up dexterity, but the benefit of more efficient walking that came by changing the shape of the foot was worth it (while humans aren't great sprinters were actually one of the best species out there for long distance walking...)

Similar to humans your species would either adapt to be good walkers by loosing the hand-like structure of the foot or they would maintain the hand structure only because they are regularly using it for climbing and thus would still have more dexterity. Given the other aspects of your creature though I'd say it's more likely it would have a more 'normal' foot, practically due to the runner build (get to that later) and partially because...

It's not fun to snap your thumb while running

Given the picture of your creature the foot structure is particularly inconvenient to run on. In particular the 'thumb' is positioned in an awkward position. If someone steps wrong they could accidentally put all their weight on their 'thumb' and snap it in half. Across all species any creature that spends most of it's time walking usually combines it's 'fingers' into a more solid landing platform that is not as easy to harm. That could be something like hooves or something like the human foot where toes exist, but we land on the much more solid back of our foot, rolling onto the ball ball of our foot, and only really use the toes to push off. In every case land animals try to have one limb landed on so it's less likely a bad step will lead to injury. That thumb looks very injury prone right now.

Claws don't work well on rock

The long talons on the foot of this creature don't seem to make sense. The legs wouldn't seem viable for attacking or defense often (especially with the posture change suggested in other answers), so the claws aren't useful as weapons. Outside of that the claws would be mildly in the way for walking/running, and significantly in the way if your creature preferred climbing on cave walls.

The only situation where I could see long claws on the foot making sense is if they are used to dig into something to get a better grip. So if the creature usually walked on land so soft, and prone to move, that the claws could dig into the dirt to give them better grip. Though even in that case I'd imagine such claws would be retractable, only used when intentional for gripping, not always present.

Get rid of those bloody horns!

I have nothing against horns themselves, many species evolve horns as part of the classic handicap principal to advertise sexual fitness. However, there is no reason for them to have blood in them. Pumping blood through the horns means the heart needs to work harder to pump blood, and if a horn is damaged it leads to major blood loss. There is nothing really living in a horn, any more then your fingernails are 'alive', so there is no blood needed to keep the horn alive. Just make the horns more similar to horns of deer or similar species.

Your species is in a hairy situation

This is really a nitpick, but having both hair and fur seems unusual. They do the same thing, there isn't much reason to evolve hair on the head in addition to fur. The most likely reason for hair to evolve was some form of fitness indicator, but since horns already serve that purpose there is no reason to have two different fitness indicators.

Like I said that's a really trivial issue. I'm sure given time I could come up with some sort of valid justification for why the creature has hair as well as fur. If you like it having hair I wouldn't suggest you remove it just because of my being overly critical :)

Are you a sprinter or a climber?

You claim the evolution of this species was focused on climbing in caves, but you gave it a number of adaptations that make more sense for a sprinter.

Most notably the tail only makes sense for a species that expects to be sprinting at high speeds and need mobility to change direction rapidly while sprinting.

However, there isn't much sprinting happening in deep caves. Climbers usually don't sprint since they use their height advantage to escape predators. So the question is why do they have sprinting build if their evolution primarily happened in caves and focused on climbing? maybe after they left the caves they lived in plains where they needed to sprint to either catch, or escape, other animals. However, if they lived in the plains so long that they had evolved to sprinting they probably wouldn't have much of their original climber build, especially the feet-hands, which are not at all conducive to sprinting!

How heavy is your tail?

Related to the question about rather this species was suppose to be a climber or a sprinter is the question of the tail's weight. To climb it will want a light tail, as any significant weight on the tail would both weigh the species down and act as a lever pulling the species away from a wall.

However, a sprinter potentially wants a decent bit of weight in their tail to help with conservation of angular momentum. and the tail as drawn looks like it would be a little heavy.

If you want a tail but don't care as much about how it looks you may want to consider switching to something more like a monkey tail. A thinner and lighter, but more muscular, tail that can be used for gripping to assist in climbing. Of course monkey tails make more sense for an arboreal creature then one that climbs on cave walls where there aren't any branches to grasp the tail on, but I'm sure you could either justify why there are things in the caves the tail could wrap around or claim the species was originally arboreal before it evolved for caves and the tail originally evolved for arboreal life found some other use to justify it's persistence later, possible just mate selection even.

Are you predator or prey?

The sprinting build and muzzle, especially it's teeth, and to a lesser extent the claws, seem to point to an evolution as a predator. However, there aren't many two legged land-based predators out there for a reason. They use to exists, and they were generally outcompeted by 4 legers which could move as fast or faster and attack easier. 2 legged predators were common back in dinosaur age, but that was as much because it was extremely hard to evolve a 4 legged posture given dinosaur physiology, in a sense you could argue 2 leg predators were a thing only because evolution hadn't gotten around to evolving 4 legged predators yet.

Before anyone says it yes humans are 2 legged and apex predictors, but we do that via technology. We are evolved primarily as generalists omnivores and only really grew into apex predators after we had reached a certain level of intellect and technology. We aren't evolved to be primarily predators or have much in the way of traits evolved primarily for predation. For the record I don't buy the claim that humans evolved for, or made heavy use of, persistence hunting in the past, but I don't want to bog this discussion down with that much nuisance.

So the question is if your species is a predator how does it hunt, and manage to not be outcompeted by other hunters? A potential answer is that four legged predators just didn't evolve in this world, but the posture of your mammal-like species suggests that four legged locomotion could easily evolve from a species similar to it so that seems unlikely.

Your species also doesn't seem to have a very effective method to make a killing blow. The fact that it has such a long muzzle implies it uses it's muzzle to bite, but it's too tall to get under the neck of the prey for a killing bite. Though perhaps if it leans far enough forward while running it's muzzle would be closer to neck height. There is still the problem that it's long neck and build doesn't seem that well suited for going in for a kill with the muzzle, the neck could be easily injured during the scuffle after a bite, you want a smaller more compact build if your going to be diving for a preys neck and holding on for dear life.

As an alternative perhaps it uses the muzzle merely to hold on to the prey and uses it's claws to kill. If it jumped onto it's prey and clung on with a strong bite it could then claw away at exposed areas but...well this still feels awkward. It's still not compact enough to cling to prey well and it doesn't seem well suited to leaping the way a raptor was.

I pray I won't be your prey

Alternatively you could have the species not be a predator but prey. The positioning of the eyes, more on the side of the head, are more suited for prey species. However, if a prey species you would expect the muzzle to be shorter (long muzzles mostly exist to make it easier to bite, and hold onto, prey species when predator goes in for the kill).

The claws may also may not make sense for prey species, but you could claim the claws on the hands were used primarily for competition over mates instead of defense from predators so it's not that hard to justify claws on the hands if you really want them.

In this approach the species would likely be an omnivore that will eat anything, but may not focus on hunting. The sprinter build would exist primarily for getting away from predator's rather then hunting prey.

Okay I think that's enough nitpicking for now :)

Answer 4

Heat dissipation

It seems you want something resembling a human in many ways. I assume this is also in activity. However, this version is unable to do long intensive work like humans can. This is all because of heat dissipation.

One of the strong human traits is the ability to sweat all over, losing heat on a large scale if needed. It is why we can do impressive bursts of activity in a short time, or run marathons, be out walking on really hot days or enjoy a sauna. Fur impedes this process a lot. It holds on to the sweat and heat, making it difficult for some of the cooling processes to do their job. Heat exhaustion and even death are very real, or the creature should be much less active in comparison to humans. Don't get me wrong, they can still be very active. Look at dogs. Some seem to be able to run around for an hour without stopping and they can travel impressive distances. However, dog owners generally also know that cooling down your dog is very important, especially on warm days. Dogs are able to exert themselves, but they reach heat limit much earlier than if a dog would have no fur and sweat glands like a human.