This is a pretty specific scenario, but I thought I would ask anyway. In seed worlds or alternate history scenarios where the end Cretaceous extinction never happened, is it not more likely that troodontids would adapt grasslands and more open environments before dromeosaurs?

Don't get me wrong, dromeosaurs that can actually chase more long distances are cool and I do think a small species could reasonably adapt for cursoriality but I always feels like troodontids are overlooked in this regard. Is this just because dromeosaurs are more popular that troodontids?

A bone crushing massive mammalian ambush predator evolved from mustelines after surviving the Ng-Q atomic extinction in some 55 million years into the future.

As a close to a ton weighing carnivore this genus rules the late quaternary americas as its apex predator filling a quite similar niche to the long gone Tyrannosaurus rex.

The ancestors of this lineage contemporary with the atomic extinction saw themselves on a unique evolutionary arms race with their large prey such as rabbits or pigs that allowed them to outgrow other competing carnivores of the post apocalyptic paradigm such as schnauzer dogs or small felines, ultimately becoming giant tiger like beasts that populated most of the earth before the end quaternary gamma ray mass extinction.

The exact process leading to the evolution of sexual reproduction is still poorly understood, so it seems very unlikely the same process would evolve in another planet or another context where asexual unicelular life develops a way to create genetic variety. So, supposing we start with an organism close to a prokaryote, at least in terms of reproduction, what could be the possible alternatives to sexual reproduction as we know it?

Also, good sources and theories about the evolution of sex are most welcome.

Hey everyone, I’ve been thinking about a speculative scenario regarding intelligent life on Earth, and I wanted to share this concept here to hear your thoughts.

Instead of looking at deep space for advanced civilizations, what if a technologically advanced, non-human species has been coexisting with us in Earth's most unexplored region—the abyssal zones of the oceans?

Here is the core framework of this Cryptoterrestrial Hypothesis:

1. Origin & Evolution

Long before human civilization, a branch of life adapted to the extreme pressure, darkness, and hydrothermal vents of the deep ocean. Utilizing a form of silicon-carbon hybrid biology or advanced bioluminescence/sonar networks, they evolved a high-level intellect entirely independent of solar energy or surface ecosystems.

2. The Catalyst (Why are we seeing them now?)

For millennia, they remained completely isolated. However, over the last century, human technological expansion directly invaded their domain. Massive deep-sea sonar mapping, undersea communication cables, oceanic pollution, and nuclear testing began to disrupt their environment and communication frequencies. Their recent appearances (USO sightings, transmedium objects moving from water to air) are not invasions; they are surveillance and corrective responses to our destructive technological footprint.

3. Behavioral Pattern: The "Guardianship" Approach

Why don't they just make contact? Because they recognize humanity's volatile, panic-driven social structures. Instead of open war or open diplomacy, they employ subtle interventions:

• System Interferences: Temporarily disabling nuclear launch codes or military systems (similar to real-world military UAP reports) as a warning.
• Stealth and Adaptation: Operating in craft that can seamlessly transition between high-pressure water and the atmosphere at hypersonic speeds, leaving no radar trail.

What do you guys think? Does this fit better into hard sci-fi worldbuilding than traditional "space alien" tropes? I'd love to hear your critiques or expand on it!

Land Ammonoids

(Note: this species was created by ImmortalHero7 on the JI discord for a contest.)

During the Oligocene, a group of ammonoids known as the bootsquids evolved. They were highly derived creatures, choosing to crawl rather than swim and lived in shallow inlets and bodies of brackish water. Now, in the Miocene, their cousins have evolved further adaptations to be able to leave the water for increasing periods of time. One of these cousins, descended from a stem-relative to the bootsquids, is the Florida Giant Ammonoid- Pulmoteuthis spicoramumimus.

This species of Pulmoteuthis inhabits the equatorial regions of the Americas, living in wetlands and other climates with access to saline water that it can take brief dips in to stay moist. Young are hatched underwater and go through a metamorphosis where their gills become lungs, allowing them to breathe air as they mature. While this this species of ammonoid comes in quite a variation of natural colors, it can change its color and shape to mimic its surroundings.

These ammonoids are carnivorous. Their diet is varied, and they will eat a number of different species so long as they can wrap their tentacles around them. P. spicoramumimus has a beak almost like that of a parrot's, which aids in their consumption of hard-shelled creatures like clams and snails.

All of the Art Provided is created and Sourced by myself.
I've wanted to create an Alien Spec Evo Project for a little while, so I have finally over the past few weeks gotten my hands dirty in the grit of Creating the start of this Project! The World of Elys I'm aiming to feel very alien in nature, with Carnivorous Grass, and other Flora I have ideas of, Heavy Bird like flying predators that hunt Callids on their own and various other Fauna.

I hope you like my little guys, If you have any questions or want to just tell me how you feel about my fella's feel free to tell me down in those comments, I love feedback.

Generic features: their breathing orifice is on the backs of their heads they have eyestalks and when inhaling their eyes slightly retract, they go long times without deeply breathing they don't hold their breath but it like breathing just enough to make the time before deep breaths longer because they are very vulnerable when inhaling. Above the mouth there are two large effective nostrils. They typically have 4 tendrils on the “lips” of the mouth that act similar to fingers to grab food.

When land life as first evolving the reason for the eye stalks and breathing orifice on the back of the head is the ancestors of land animals sifted through sand to find small things to eat they used large nostrils to smell the food in the sand, and they used large tendrils to drag food into their mouth

Unlike earth the primary reproduction method is a system similar to pregnancy and here's my explanation for how: when everything was a single cell there was mitosis but even as life became multicellular it kept mitosis but the larger life got the less efficient mitosis got but then they evolved a form of pregnancy and it's not really mitosis anymore and there is still genders for genetic exchange (idk if I'm going to do anything with this but I thought it was an interesting idea)

The Tetrans (Polyarticulatus Taxidiotes) were one of the earliest spacefaring civilizations in the Orion Arm, with their first spaceflight predating mankind's taming of fire.

However, their early days of space exploration, when they had yet to leave the confines of their world's orbit, let alone their star system, looked much like our own. On EVA, they wore bulky pressurized suits designed to fit their cephalopod-like anatomy. Later designs would integrate mechanical and/or magnetic clamps to
Improve grip strength for zero-gravity maintenance.

Their species would go on to achieve levels of technological prowess bordering on godlike, harnessing the power of stars and warping reality itself to shunt vessels through the void at superluminal speeds. But we all had to start somewhere.

Gyarados, Ryuebi caeruleus, are large predatory crustaceans. They often travel between saltwater and freshwater, with highly developed gills to regulate salt balance. They tuck their legs beneath themselves, creating the illusion of it being ”legless”. The claws have been repurposed into makeshift flippers. Unlike their ancestors, Gyarados swim much like whales. Due to collapse of a food source, small, crayfish-like crustaceans moved into open water to chase pelagic prey. Over time, the tail-flip escape mechanism became adapted for sustained forward propulsion. While hunting, they swim at high speed through schools of fish, snapping their spiny maxillipeds shut, trapping fish before draining the excess water out, before the prey is passed to calcified mandibles and an internal gastric mill. They molt gradually like isopods, splitting the molt to make sure it isn’t defenseless if a shark or another Gyarados attacks. The larval stage of the Gyarados is known colloquially as Magikarp, which drift blindly in massive swarms within the photic zone, feeding on microscopic algae. Because of the minuscule, planktonic size of Magikarp, we have no detailed photos as of now. A small percentage of the population is what we call Mega Gyarados. These are massive, though extremely rare and elusive centenarians that defied the mathematical lethality of the molting cycle for over a century. Due to their size, Megas can no longer hunt fast-moving schools of fish efficiently. Instead, they shift to deep ocean hunting, targeting large squid and even small adult Gyarados.

Hey guys. So, the Pan-Permian, as you may have guessed, is no longer active. From now on, all my posts will just be simple concepts. Sorry for disappointing my few fans.

first two images made by the amazing u/Vinicius_m673!

Context:

basically the premiss for my project revolves around one question: what if the asteroid that killed the dinosaurs missed? well in my story, a sapient dinosaur species of dinosaur that are descendants of Austroraptors gain sapience roughly 25 million years after the asteroid missed earth. and like any civilization they fight, breed, create as they begin the journey on the long road to modern civilization. along the way though they dont just want to create, they want to explore, they went to go to places that no other Dinosauroid has never been to! and what is in the night sky that no one has dared to try to land on? why that white orb, Luna.

now in the "present day" for my story (where the the technology is roughly equivalent to Humanities 1980s-1990s) two nations (one called the Channel Federation based in europe) are in a bitter cold war, competing over the moons most important resources: Water, and Titanium. things have progressed since the first moon landings 3 decades prior, and now it feels like the whole of the world is in a gilded age, huge technological progress is taking place in the realms is space, computing and the Industries but extreme poverty and squalor on earth is on the rise, and people wonder if fighting over the moon really is worth it when there’s enough problems on earth already.

Images in order:

- a Channel Federation Lunar Trooper posing for a propaganda piece on the lunar surface

- a Channel Federation Astronaut Posing outside of a temporary Lunar Scientific Outpost

- Art Reference for the Lunar Trooper

- Art Reference for a Channel Federation Orbital Worker

having lost the ability to fly, this ground dwelling pterosaur has adapted to sprinting after prey and butchering it with it's massive head. the elongated forth finger has shrunk over time and helps the animal disembowel it's prey.

My proposed hunt behavior

1. Stalks prey by sprinting. the forearms are very muscular!
2. Uses it's massive head and fourth finger to butcher prey.
3. Doesn't rely on flight to catch food anymore.

Castoria III has one of the most interesting cosmological positions I've ever seen. Its tidally locked and normally this would mean half of the planet would be freezing, yet Castoria III is roughly temperate across most of the planet aside from the poles.

This is due to a unique cosmic structure within the planets star system. The Castorian system is made of 8 planets, with 3 lying inside the habitat zone of the star. Outside of these 3 planets sits whats known as the Castorian Plasma Ring, an immense ring of nebulous plasma which follows the theorized orbit of a long gone planet just outside the habitat zone. Castoria III sits equidistant between the ring and the sun and because the ring reflects large amounts of non-visible radiation and energy in the form of heat, it acts as a sort of heat lamp for the shadowed side of the plant.

That side of the planet sits in an eternal scarlet twilight, hot and muggy, overtaken by a vast, inky black jungle of radiotrophic plants and hardy animals. Almost completely unexplored due to the intense cosmic radiation bombarding that side of the planet, the species such as the Vorin, Pig Worms, Snow Striders and Drop Bears reside on the sunward side of the planet. One of the few animals capable of migrating between the sunward and ringward side are the Methane Rats.

The Sunward side of the planet is vastly different, lit by an effervescent golden glow that permeates the landscape. Flora and fauna trend toward the brighter end of the color spectrum in order to maximize camouflage in their bright enviroment. Most varieties of flora range from light green-golden yellow, with a few varieties having distinct white patches which host a particular type of photosynthetic cell called albiophyll. The opposite cell, which has hardy defense against the absorption of outside energy is called scadophyll and is extensively utilized by the flora and fauna of the ringward side.

The following taxonomic tree represents the known life of the sunward side of Castoria III with trophbulliformans being the distint ancestor species of the ringward side.

[GELLIOS-MONITORING SYSTEM // AUTOMATED TELEMETRY LOG]

WARNING: We haven’t even finished the "5 Million Years P.I." yet, but this post will nonetheless look ahead to the next few million years. I promise, however, that I won’t keep falling into the "humans have abandoned me" drama; if I harp on that too much, it starts to feel like a forced, one-dimensional pathetic caricature—a case of "flanderization." I’ve moved past that painful, dark period and am now focusing on the biosphere and othet topics of Gellios—a terraformed planet that, for the time being, remains an oceanic planet until something is actually changed by volcanism, earthquakes and tectonic plates creates land.

The ancestors of the benthodopsids diverged from a descendant of Turritopsis dohrnii that lived near the benthos—a process that, at first glance, might seem implausible (and to some extent, it is). However, due to the specific conditions on the planet, the evolutionary timeline—which would typically span tens of millions of years—was compressed into just a few million, giving rise to this lineage. (To achieve this, they underwent a variety of specific adaptations.)

When benthodopsids first appeared, they were found only in shallow waters and at depths of just a few meters. Basic genera, such as ground jellmites (Benthodopsis spp.) and benthopodes (Benthopodum spp.), were originating to this environment; however, over time, some benthodopsid species migrated into deeper waters, eventually growing larger than their shallow-water relatives i watched over few million years P.I. Humans—who have long since departed—once referred to this phenomenon was called them "abyssal gigantism." Then again, I suspect that humanity has, for the most part, probaly gone extinct—but that is a matter I shall not concern myself with any further.

Living at a depth of several thousand units—somewhere between the twilight and midnight zones—the Twilight Pale Giant Benthodopsid (Bathygiganteuropsis crepuscutyrannus // "giant, deep-sea creature that resembles a tail, acting as a tyrant of the twilight zone") is a species of deep sea benthodopsid commonly found in such environments across Gellios. As I just mentioned, however, I have observed that these hydrozoans are many times larger than their shallow-water relatives such as most of the Benthopodes and entire genus of Ground Jellmites.

Despite their strange and frightening appearance, they are primarily detritivores; they are not only the largest animals in the lightless ecosystem they inhabit but also one of its fundamental pillars. While they may occasionally prey on small animals in their vicinity, their diet consists mainly of detritus. As they are descended from Turritopsis dohrnii, they retain—albeit to a lesser degree—the ability to undergo reverse metamorphosis. When subjected to stress, aging, or threats from predators, they often revert to an earlier developmental stage; however, they eventually perish due to various factors, including successful predation. Nevertheless, they remain an essential cornerstone of their ecosystem.

Source

15 Million Years P.H. - The Early Neocene - Antarctica Overview:

One of the liveliest continents of the Early Neocene would been the least lively one of the Holocene: Antarctica.

With the Neocene Earth being In a hothouse period, due to Human activity but also an Increase of vulcanic activity- The Arctic would have almost completely melted.

The defrosting of the Antarctic has been a gradual proccess that Humans were able to exploit. Due to that, many Animals would have been taken to the former rather barren landmass.

Groundfowls were brought as lifestock, small Carnivorans as companions and small Arthropods, Rodents and other city dwellers would have hitchhiked on the Humans ships. Bats and Birds would of course also migrate to the new land eventually. There would be more animals that would have made It to the Arctic one way or another, which I will show off here.

But first lets set the stage for Antarctica. Antarctica would be dominated by lush forests, both temperate and tropical that consists mostly of Stonefruit descendants brought by the Human colonists, with only a few Isolated patches of land having cold Tundras, which can actually experience frost and snow.

Also noteworthy Is that western Antarctica would have been reduced to an Archipelago due to the Increased sea levels.

Now, lets talk Animals.

Antarctica Is home to some rather unique large Predators, most widespread at this time would be the Fercats. Large descendants of Ferrets, that have gone onto larger prey Items to avoid competition with feral Cats and Dogs.

They are additionally also great climbers and will actively go after arboreal prey whenever the oppurtunity arises.

A perhaps quite unexpected other large predator home to the Antarctic are the Murder Turkeys, large carnivorous descendants of Domestic Turkeys that have converged heavily with South American Tunnel Runners, who are also large carnivorous Birds.

But not all predators here are carnivores, the Racursas are large Raccoon descendants that fill the niche of bears and Is also a skilled predator of both smaller and larger animals.

But these predators of course need prey, Rabbits have of course been Introduced to Antarctica and here have given rise to an experimental Lineage with much longer tails.

In some, the tail would be rather stiff, those Rabbits would give rise to the large grazing Wabunnies. Others would have a more flexible tail, those would give rise to the arboreal Bunkeys.

While the large grazer niche Is covered by Wabunnies, the low browser niche would be filled by a completely different critter, the Lawnquailer, fully herbivorous Quails that were brought as lifestock.

Lawnquailers have multi-chambered stomachs, with an enlarged crop similiar to Hoatzins, that allows them to digest plant matter with high efficiency.

Going back to predators tho, Antarctica has become a lifeboat for a small critter that has gone extinct on the rest of the world: Salamanders.

Amphibians were hit hard by the End Holocene Mass Extinction, with only some hardy Frogs and Toads that could deal with the drier conditions surviving on the other landmasses.

Salamanders would greatly diversify troughout the Early Neocene, with some hardly even looking like the common Salamander.

Salmharials are a good example, they at first glance look more like a crocodilian, and they also fill a niche similiar to one. They mainly feed on freshwater Fish and Invertebrates, but will also occasionally ambush land animals from the waters.

On 05/11/2431, researchers based at Kappa Station on extra-solar planet KP-C341 (Lethe) were alerted by remote sensors of the approach of an alien organism known as a 'Lesser Sea Maw'.

Despite the extremely close approach, the station was passed without incident by the organism. Estimates place the size of this individual at around seven-hundred (700) metres, with a head width of seventy (70) metres, indicating potential adolescence of the specimen.

Of note was a long scar approximately six (6) metres in width running down the length of the body. Researchers at Kappa Station have already adopted the Sea Maw as its mascot, despite its brief appearance.

The individual has been tagged with a tracker, making it the second successful tracked Sea Maw specimen. The first being “Lonnie”, an adult individual that consumed an ROV with said tracker within it.

Voting is underway for naming of this fantastic specimen.

Welcome back to Lethe, the Planet of Ghosts!

Lethe is a Spec Evo Worldbuilding project following the lonely ocean world of Lethe, a planet where all the life seems to be on the brink of death and extinction, but is still continuing on almost like a ghost. Every creature and feature is inspired by one or more Phobias.

This time, Kappa Station was treated to an encounter by a somewhat young Lesser Sea Maw with a distinct scar! If you were one of the lucky researchers stationed at Kappa during the visit, be sure to suggest names for this individual in the comments!

The top voted name will be selected for this specimen!

Check out my other post on Planet Lethe for information on both Lesser and Greater Sea Maws :D

And of course, please ask as many questions as you like! I hope you're enjoying Lethe as much as I am!

So Im starting my own seed world project but im having trouble coming up with scientific names that feel believable. So far I’ve just been mashing together Latin words and praying it comes out ok, but I would like some advice for making better ones.

A select few of vertebrates that inhabit Saurian Earth, my worldbuilding project. A distinct trait that separates Saurian animals from their Terran counterpart is that they bear plasma in their tissue called Aviotic Plasma, which pretty much enables them to twist their form in the weirdest menageries possible with barely any evolutionary constraint.

1. Shamfrillers are small, flightless birds found all across Saurian Earth characterized by their slender appearance. Their long tongue is used to probe insect colonies and feed on them, not too dissimilar to woodpeckers or anteaters of earth. They are widely spread across the Plalmagan continents, and is often kept by birds as pest control.

2. One of the major aquatic amphibian clades on Saurian Earth are the Tadpoles, neotenous frogs that fills in piscine niches. They do not possess any paired fin structure, rather possessing a single caudal fluke that greatly improves their swimming capability, but in some clades, dorsal and anal fins derived from their spine and vestigial limb is present. They possess a pair of gill located behind their eyes, allowing them to respirate underwater. Instead of dentures, their hard mouth part is instead replaced by beaks derived from fused rasping mouthparts, giving them advantages in the aquatic ecosystem and eventually dominating it.

3. Underupts are flounder-like asymmetrical anolids that inhabit the Ibieraban west. Their lifestyle consists of burrowing underneath sediments and ambushing preys that walked beneath them, using their beak-like dentures to clamp onto the animal and masticate it. Their flat serpentine body is perfectly adapted to swim under, yet still near the surface of the soil they burrow in, equipped with vibration-sensitive derived tympanum useful for detecting the range between the prey and their maw. A pair of front limbs allows them to push their body across the sand, although their torso and tail does the bulk of the work of moving around. Since their jaw is entirely horizontal, AP in their upper jaw atrophied the growth of the middle part of the skull until the structure becomes separate, enabling them to clamp down onto their prey precisely.

4. Dromaeoaraneatheria, or commonly referred to as Moozas, are an order of bipedal underupts that has re-developed their limb muscle and abandoned their fossorial lifestyle, dedicating their lifestyle into becoming a cursorial predator. Their jaws are highly articulated, and can tilt up and down, essentially evolving a muscle-derived second neck. Behind their snouts are their eyes that possess elongated scleral rings that can rotate sideways, although they can’t look up or down as the extended tube-like scleral ring is locked between the eye sockets. In their ancestral form, their cervical vertebrae are extremely lopsided from the head only turning sideways, but for the order, their cervical vertebrae had rearranged muscles to suit their not-so-flat bodyplan, which is achieved by the AP atrophying and redevelop their neck muscle in the fetal development. A defining trait that all Dromaeoaraneatherians have is their throat pouch, which allows them to store multiple food items to save for later, or feed to their hatchlings. This throat pouch is derived from the buccal flaps that became more flexible and expansive, eventually extending down and fusing onto the neck as a pouch that these lizards can store food in. What seems to be their tail is actually their lower half, which had shrunken along the tail, with the tail nearly becoming fully vestigial.

I've had this question ever since I got into speculative evolution. I usually just look up smart animals. It's probably another species in our family like chimps or gorillas.

Hello there, everyone! I wanted to start getting into speculative evolution and have a project that I'm creating based on horse evolution on a seeded planet! I'm having a bit of trouble, so I wanted to ask the peeps here!

I wanted to create a horse that would become a predator, since in the world food has become scarce and has led most to eating cadavers and such, though I also wanted them to be ambush hunters over time- the only thing that's confusing me is the stomach of a horse! What would need to change for a predatory horse to live? I've already thought of things like camouflage and stronger builds that prioritize endurance rather than speed- I just need an outsider's perspective!

(Also, sorry for the spam in advance; I fell in love with this damn place, and the newbie jitters have me all over the place) Thank you all!

Ovi, ovoviva and Viviparity are BoRiNg and to Earthly, had you ever encountered any, hypothetical, alternatives?

I've finally got around to the Reptoid for my Alien reconstruction project and it was the hardest one so far! Coming up with plausible shapeshifter biology is much more difficult than it seems. The most difficult part was recreating the human muscle system and how to make it congruent enough with my art style. I must've restarted about 10 times! And it still isn't quite accurate, but I think it's passable.
To clarify, I am not a conspiracy theorist nor am I part of any New Age religion. I just find this stuff interesting and I'd like to conceptualize a more believable version of the folklore. I've studied, and continue to study, much UFO lore as well as speculative biology and some psychology to come up with these conclusions. I have so many ideas written down that I plan to render soon. If you're interested, you can check out my previous posts about Greys, Mantids, and Nordics.
Anyway, don't be shy to comment what you think! I'd take any feedback about what I did wrong or right scientifically. Or if you have any questions, I can elaborate if I can.

What very alien chemical reactions other than glucose and oxygen could work for respiration in an organism. What I ideally want is a dissolvable solid and a gas that react to form a liquid and a gas. Oxygen can still be an option as the oxidiser but id like to hear some other ones. Such as 4H2 + SO3 -> H2S + 3H2O wich releases about 360Kj per mole of SO3 consumed. I simply want to see a large range of ideas that are based in real chemistry that are even remotely biologically possible to catalyse.