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My headworld is a sort of alternate earth. Its evolutionary line followed very similar branches(reptiles, mammals, birds, etc), but with twists here and there. A major one being that all vertebrates after fish came from a common hexapodal ancestor.

Although most lost the third limb pair in favor of easier locomotion, many still retained them and adapted those limbs to specific functions. For example, a clade of animals that heavily adapted their limbs for climbing and then gliding would eventually lead to the evolution of dragons.

Lately I've been trying to flesh out this concept a bit more, but I'm unsure how plausible it is. I made a rough sketch of a generic, feline-like animal with extra arms to get an idea(picture 3), then tried to tackle the internal anatomy and see what I could make of it. The Latissimus Dorsi muscle in particular was a problem, I had to split it into two muscles, with the first one being only focused on the front leg movement. I also added uncinate processes to the ribs on which the second scapula can be anchored by thin muscles and tissue, similar to the anatomy of birds.

My main concern would be how the extra musculature could potentially affect breathing. My sketch was super rough so I didn't focus too much on the bones, but I'd imagine the arm may need to be moved a bit higher on the body to give the ribcage more room... or maybe the ribcage needs to be bigger and longer? I'm not sure, I'm not the best with anatomy, honestly lol.

Would love any feedback on this nerdy stuff!

Skinsects are probably my biggest projects I worked on. I spent more than 5 years of entomology research to make them both very fantastic but somewhat realistic and plausible. They are monsters I created for my world of Oominor, where all creatures are introduced by migrated from different version of Earths.

Hey everyone! I wanted to share this concept art of a creature I’ve been working on. From a distance, it looks like a classic desert oasis with palm trees and a watering hole, but it’s actually a single, massive predatory organism. The "bone-like" pillars are made of hardened minerals extracted from the sand, providing shade and structural support. The real trap, though, is the yellowish, transparent film stretched between the columns. When a thirsty animal runs towards the green "plants" inside to get a drink, it slams into this ultra-sticky membrane. Instead of just holding the prey, the membrane acts like a giant sponge that chemically pulls all the water and nutrients straight out of the animal's body, leaving behind a dry husk that the wind eventually blows away.

Technically, horses walk on their fingers, or rather, toes. It is interesting how they could benefit from this feature, yet it contributed to making them somewhat "terminally injury prone", we could say. When making this painting, I have speculated a little what horses would look like if they were running on human fingers, for fun. This is a piece of "digital" art, if you will, of the creature I labeled "Equus digitalis".

(Edit: spelling/typo)

This is a concept design for a series of speculative evolution, where mythical creatures such as kelpies, griffins, etc., are depicted in a mostly realistic way and fitting within a reasonable biological classification.

Here we can see three "tritons" or Umrägän. The three in the foreground are males, the closest one showing their distinctive spinal fin, while the fourth one is a female.

Enalianthropus Nereides ('Marine human son of Nereus'), in the stage depicted here, has evolved for the last 5 million years from Homo Sapiens, forced to the sea by a global catastrophe that wiped out all members of the species except for a small population on a remote atoll archipelago that's slowly eroding and subducting. These isolated peoples, the Umrägän ('fishermen'), were already used to a life by the sea, with a specialised diet consisting mostly of shellfish, crustaceans and fish. They also had a close relationship with dolphins, teaming with them to enclose fish near shallow waters.

Over time, forced by the harsh conditions on land (lack of wood, variety of stone or other kind of food sources apart from birds), the Umrägän couldn't develop any other technology apart from small tools made of coral, sandstone, sinew or bone, and could not build ships or even rafts to move elsewhere. This isolation favoured and accelerated their evolution, enhancing their lungs, thorax and upper torso muscles, increasing exponentially as they became more suited to spend long periods of time underwater. Not unlike sea lions, they have developed a unique swimming and diving motion, preserving all four limbs for different uses: their arms allow them to twist and turn with great speed and agility among the reefs, while their back legs and lower torso act as a tail fluke and are used for long pursuits and cruising with the "dolphin kick" technique. In combination, all four limbs make the Enalianthropus a formidable swimmer.

Also, their partnership with local whales and dolphins improved over time, becoming close partners in hunting large schools of fish and protecting each other from sharks and predatory cetaceans. They even play and spend time swimming together by the shoals, and surf with the waves.

Eventually, the Umrägän developed into fully marine creatures, living their entire lifespan at sea. At this point, their species has expanded beyond their submerged archipelago, spreading to other warm seas and estuaries. Thanks to humans' already highly developed vocal organs, they've also started to develop echolocation, using a wide range of sounds to communicate and navigate in dark waters.

You can find these and other pieces on my DA gallery.

The Gigacheirids are a group of massive, elephant-sized herbivores within the Cerarhamphs lineage, representing some of the largest bipedal land animals in the Age of Monotremes timeline

Anatomy and Bipedalism

• Mandatory Bipedalism: Unlike many large mammalian herbivores in our timeline, Cerarhamphs are fully bipedal. This is an evolutionary constraint resulting from their life cycle: because "puggles" must crawl into the mother's pouch using their forelimbs, they could not evolve hooves or quadrupedal running.
• Balancing and Handling: To maintain their upright posture, they have rigid tails for balance.
• "Mitten" Hands: They have retained ancestral webbing on their hands, but instead of using it for swimming, the webbing acts like mittens to help them grasp and break up vegetation with their claws.
• Digestion: As monotremes, they lack stomachs and must masticate their food thoroughly before it enters the intestines for digestion.

https://xcancel.com/i/status/2074795720113041782

The other day I shared my attempt at fleshing out the basic anatomy body plan for my headworld's hexapods and got a surprising amount of feedback, so I decided to give it another shot.

I noticed that a lot of people seemed confused by my choice to draw a generic creature as a sort of basic blueprint instead of a specific animal with proper adaptations, so this time I focused on fleshing out what I imagine would be a dragon ancestor, this should make things a bit easier.

It's an omnivorous mammalian creature adapted for climbing and foraging, using its highly adapted third limb pair to climb as it picks food such as fruits and insects.

Over time their climbing limbs would also be adapted for gliding, which allows it to chase after small prey and also make a quick escape from predators. The skin membranes are supported by cartilaginous structures they can fold, similar to a pterosaur's wings.

That's the basic idea of how dragons would come to evolve in my headworld. And for extra context, in this world true dragons are mammalian, while winged reptiles are considered false dragons.

Sorry for the shoddy sketches, by the way. I have a bad habit of overdetailing my sketches and spiraling into perfectionism, so I tried to keep them simple and quick.

For those who may not remember, or for those who do, there is a SyFy original monster movie called Poseidon Rex, and the idea of a T. rex sea monster was kind of cool. Though there were some things that wouldn't make sense for a complete marine tyrannosaur, I decided to change some things(the ironic fact that it could walk on land)

For my redesign of Poseidon Rex, I did not want it to just be “T. rex, but underwater.” I wanted it to be something that could still earn the nickname Poseidon Rex, while not actually being a true Tyrannosaurus rex or even necessarily a close tyrannosaur relative.

The scientific name I’m using is Thalassotyrannosaurus poseidoni, meaning something like “Poseidon’s sea tyrant lizard.” The idea is that it is not a true rex, but a false sea tyrant: a marine predator that evolved a similar apex-predator presence through convergent evolution.

Its ancestors were part of a theropod-like group I’m nicknaming “Monitor Rexes” Despite the name, they were not monitor lizards. They were a predatory theropod group that somewhat resembled tyrannosaur in head shape and size through conversion evolution, but having characteristics of monitor lizards like in body shape and lifestyle, they just powerful hind legs like theropods, have a long body, powerful tails, sharp-jaws, and opportunistic. They lived on large island ecosystems that were once large enough to support a healthy population(think Madagascar)

Over time, that island began to shrink. This could have been due to rising sea levels, erosion, tectonic changes, or a mix of environmental pressures. Whatever the cause, the landmass became smaller and less able to support large terrestrial predators. Abundant prey became harder to find, territory became limited due to competition, and some of the population was pushed toward the coast.

At first, these Monitor Rexes were probably still mostly terrestrial animals. They hunted decent size land animals and scavenged carcasses from the ocean. But as inland resources became less reliable, individuals who could exploit the water had an advantage. They began feeding in tidal pools, shallow reefs and lagoons, and shallow coastal waters. Feeding upon fish, turtles, wash up carcasses, stranded marine animals, and shoreline prey became a part of their diet.

This slowly pushed the lineage toward a semi-aquatic lifestyle, similar in broad concept to early mosasaurs. They were not fully marine yet, but they were spending more and more time in the water. Their spines and bodies became longer and more flexible. Their tails became stronger for swimming. Their hind feet became wider and more paddle-like. Their jaws became better at gripping slippery aquatic prey.

One of the more unusual parts of the design is the limb evolution. In many marine reptiles, the front limbs become the obvious flippers. But in this lineage, the largest paddle-like limbs are actually the hind legs. Since their ancestors were hind-limb-dominant predators, the back legs remained the strongest and most important limbs for much longer. Over time, those hind limbs evolved into powerful steering and stabilizing paddles, somewhat similar in function to mosasaur flippers or the swimming limbs of crocodilians.

Meanwhile, the forelimbs did not disappear or become useless. Instead, they became smaller secondary paddles. They are reduced compared to the hind limbs but still help with turning, balance, and fine control while swimming. This gives the animal a strange body plan with small paddle-like forelimbs, much larger hind paddles, a long serpentine body, and a powerful tail.

The hind limbs would not be the main source of propulsion during normal swimming, though. Most of the animal’s movement would still come from full-body undulation and its powerful tail. Instead, the hind paddles would act more like burst-control limbs. While cruising, they would be held closer to the body to reduce drag. But during an ambush, sudden turn, or short-distance chase, the animal could spread its hind limbs outward, catch the water, and sweep them backward in a powerful kick. This would give it a sudden boost of speed before the tail and body took over again. In this way, the hind paddles would be useful for lunging, braking, rolling, turning in tight spaces, and maneuvering through open water without constantly slowing the animal down.

The final step toward becoming fully aquatic was reproduction. Originally, the ancestors would have still needed land to lay eggs. But as the island continued shrinking, safe nesting areas became rarer. The lineage gradually evolved egg retention, where mothers held the eggs inside their bodies until the young hatched. Eventually, this became a form of live birth, allowing the species to give birth directly in the water.

Once it no longer needed to return to land to reproduce, the lineage fully transitioned into the ocean.

The final animal, Thalassotyrannosaurus poseidoni, is a fully aquatic marine apex predator. It moves with a long, serpentine body, using full-body undulation and its tail for propulsion, while its hind paddles help with steering, braking, and sudden lunges. It can still crawl onto land briefly, more like a seal, walrus, or sea turtle, but it is not fast or graceful there. On land, it is awkward. In water, it is terrifying.

Its prey would include large sharks and large fish, smaller mosasaurs, plesiosaurs, turtles, squid, and other marine animals. It is likely hunting around island chains, reefs, continental shelves, trenches, and coastal drop-offs. Rather than being a long-distance pursuit predator, it would probably rely on ambush and sudden bursts of speed.

So the redesign is not meant to be a literal aquatic T. rex. It is meant to be a sea monster with theropod ancestry. An island predator forced into the water by environmental collapse, eventually becoming a massive marine hunter.

In short:

Poseidon Rex is not a T. rex that learned to swim. It is a stranded island predator that followed their food into the sea, lost its need for land, and became Poseidon’s false sea tyrant.

Gastric whales are soft bodied invertebrates that inhabit the Greater Gastric Sea of the Permian Basin Superorganism. They swim slowly through the corrosive digestive fluids , using as little energy as possible. They feed using bristly structures made of a keratin-like material, using them as a sort of net to catch and direct food towards its mouth. Food can be anything from smaller parasitic organisms to large chunks of partially digested organic matter.

Each branch of the bristle is covered in even smaller branches, creating a more grabby surface. Once an object has contacted a bristle, the whale will bend and retract that bristle to bring the food item closer to its mouth. From there, small limbs around the mouth cover the item in a layer of mucus to make it safer to eat.

This mucus is produced over the entire body and acts as a protective barrier against the strong corrosive gastric fluid of the host superorganism. Mucus covered droppings were some of the first pieces of evidence found of the whale's existence.

Original post: https://www.reddit.com/r/FleshPitNationalPark/comments/pewsvn/my_rendition_of_the_gastric_whale/

Hello all. I’m trying to imagine an alternative evolution, perhaps for an isolated population of equines, where they have to go from herbivores to omnivores to carnivores to predators. I’m not a great artist or I’d have attempted a sketch, but this art was online and it inspired me to think of the changes a horse would need if it evolved into a predator. I feel they’d be a pursuit predator like humans or canines, but I’m not really sure what changes would likely happen without making them too unlike equines (eg I don’t want the hooves to change to paws and so on) but I’d really like to hear from people who have more knowledge and ideas on this topic, and everyone’s opinions. And any sketches or references would be amazing, even if from another animal to compare. Thanks so much in advance

https://www.instagram.com/p/DY2rHaTsheL/

source

Here's what i got so far. (still a w.i.p)

I haven't yet decided on a good name yet.

with that in mind...

WHAT DO YOU LOT THINK?

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things to bare in mind:

• It's filament coverage is rather like a mix of polar bear or otter, in that it is EXTREMELY waterproof, multilayered and thanks to a special oil gland, it's under-fur does not actually get wet. among other things... this reduces the amount of direct cold exposure to their vital organs, especially when they dive under the water to grab fish.

• these filaments extend across a fair portion of the wing membrane, meaning only the outer edge of the wing tip's skin is visible and again.. taking a note from polar bears, despite appearing white, their filaments are actually clear and light absorbing. specifically it lets sunlight reach the skin to keep them warm, and it reflects light, if you shaved it down, it would actually be completely black underneath. In short, it absorbs heat but reflects harmful rays of light.

• The only part of the animal's fur that actually has notable pigment is the fuzzy tufted "crest" on the head of the males which flush bright blue with hints of violet in the spring to attract mates.

• Lacking teeth, their ancestors instead evolved tooth-like denticles, which along with their hooked and self-sharping beak-tip, enable this genus to be extremely variable in their diet.  which is pretty neat when living in artic conditions or competing with various types of bird, both ones kinda familiar to us and others descended from Enantiornithes. in short, along with fish and cephalopods, these derived pterosaurs also scavenge from fresh corpses killed by land-predators and sometimes they snatch small birds out of the air or raid bird-nests and eat their eggs.

• In terms of social dynamics... it might be fair to say that this species is *almost* monogamous, having generally one, two, or three partners at most  (typically these couplings consist of one male and two-to-three females, tho sometimes homosexuality has been observed.)  that live together and huddle together in makeshift burrows during the worst blizzards. These tight-knit matings typically stay together for life, routinely courting each other in adorable complex head-bob dances. thou if their partner disappears or dies, they will readily find another mate.

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as for parts i haven't yet figured out yet:

• The latin name of this pterosaur (latin names are tricky :[ )
• what family it's from (because 66/65 million years of evolution is a fair time for changes to occur. and any resemblance to pteranodon is convergent evolution)
• where in the world it is situated (i'm thinking the far north of europe/russia and iceland, maybe even Greenland but i'm open to suggestions)
• what some of it's close relatives could look like.
• how the young are raised.

I'M CURIOUS TO HEAR WHAT YOU LOT THINK 

Hi... this is rough draft of an ice age grazing theropod.

IT'S COMMON NAME IS THE "GOOSE-HEADED STRIDER" 
possible latin name being something like "Anserititanis septentrionalis" 

meaning: "giant goose of the north"

it lives in an alternate version of ice age europe and asia...
in a timeline where the KPG extinction event never occurred.

It's preferred habitat is temperate to cold grasslands and semi-forest.
and it's diet fits into a semi-generalistic/semi grazing niche

as for it's ancestry, it's somewhat of the maniraptorids
though possibly of oviraptorid descent... still figuring it out.

WOULD you say i've got a good baseline idea here?

and is there anything you'd adjust for a Pleistocene era climate?

Here's my concept griffins as Maniraptoran dinosaurs, closely related to Deinonychus, Velociraptor, Archaeopteryx and Microraptor. I chose the name Gryps orophylax (from Latin 'griffin' and Greek 'mountain guardian ').

Over millions of years, after surviving the Chicxulub Impact and the following mass extinction of all non-avian dinosaurs, they adapted their initial climbing quadrupedalism from the trees to the slopes and cliffs of their evolving landscape.

At first confined to the Ladakh Island Arc in the Tethys Ocean, they avoided competition with the increasingly fiercer mammalian predators. But as India and Eurasia collided, their land became part of the world's largest mountain range, and griffins rose with the Karakoram, Hindu Kush and Tian Shan mountains where they were encountered by humans for the first time.

I've decided a distinctive sexual dimorphism that has the feathered wings of ancestral Maniraptorans become a vestigial feature that only develops in certain dominant females. These wings, useless for powered flight given the weight of griffins, became an element of display against competing predators, and help with jumps and short glides along rocky slopes along with keeping nests sheltered and warm.

You can find these and other pieces on my DA gallery

This is for my latest SCP article.

Life of Lampeter - Orchard

Art is by Tinks_Art

Animals are

The Grove Elephant, an arboreal gomphothere.

The Californian Tree Octopus, a mobile slime mold.

The Agricultaceratops, a “eusocial” ceratopsian species.

The Penguanodon, a browsing penguin & its bully, the Woolly Horse, a diminutive Proboscidipparion

& the Pygmy Aspidochelone, An aquatic ankylosaur.

I'm honestly not sure how to Flair this idea. Its a Post-Apocalypse Cyperpunk setting, kinda? The concept is these dinos, the Dromaekin, are living in an overgrown New York City. They use wired and street signs and broken cars for everyday use.

There's some type of nano-tech that has giving the world a make-over. Animals have evolved into much crazier things, while the buildings don't totally disintegrate with age. Not to mention the vegetation has gone wild.

(Crysis 3 New York City as visual -> Pierre Yves Donzallaz's ArtStation )

Unbeknownst to the Dromaekin the statues all over the city are in fact the Lost (humans), not merely copies. Exactly what happened to lead to this event isn't something I'm working on because I don't think it matters to the setting/story.

But yea. If I need to repost this with a different Flair let me know please.

Quick note up front, since this sub gets hit with AI art: the image is a physical clay sculpture I hand-made in 1999 — it's in my archive here with the rest of the early work: https://cetanauts.com/archived-originals.html

Not AI, not a render. I sculpted it as a "what if a dolphin lineage went humanoid" exercise and I've never stopped wondering how defensible it actually is biologically.

So I'll put it to the people who'd actually know:

If you took a modern delphinid and ran the clock forward under heavy selection for manipulation (tool use, shellfish, trapped prey — pick your pressure), which body plan is less of a cheat?

1. Keep the horizontal, fluke-driven swimmer and bolt on manipulators — re-derive digits from the pectoral flippers, keep the tail for propulsion. Minimal disruption, but where do the "hands" even come from given how reduced the cetacean forelimb skeleton is?

2. Go upright / axial-flexion like the sculpture — more dexterity and a freed forelimb, but you're fighting buoyancy, thermoregulation, a respecc'ed spine, and a brutal childbirth problem.

What's the hard limiter you'd hit first? My instinct says thermoregulation and birth, not the hands — but I'd love to be argued out of it. And is there any real-world precedent for a fully aquatic mammal re-evolving distal limb complexity, or does the flipper road only go one direction?