So, we've got some new editors recently. As I've never seen any of them before, they may very well have some people who are new to speculative evolution in general. Therefore, I am attempting to create a resource similar to that of the SCP Foundation's "List of Overused SCP Cliches" or whatever it is called.
This is not a list of "don't do this ever" it is a list of "if you do this, you should have several paragraphs of excellent reasoning backing it up or you're going to get called out on it." This is not directed at a person or project. This is a work in progress; if you have ideas leave them in the comments section, and either I'll talk about them or I'll add them.
- General Tropes -- Certain things are really common. I've seen them, you've probably seen them. They don't have to do with specific species, so to speak, but interpretations of species. Sort of.
- Things that look like other things that are prehistoric -- Let's look at prehistoric carnivores. Not prehistoric members of Carnivora, but prehistoric carnivores. That includes the ancestors of whales. Take a good look. Notice how they're not all that close, all things considered? Well, given that evolution doesn't make things that look like other things that came before aforementioned thing, why should speculative evolution? Sure, it can be useful, especially over short timespans, to give an image as an example, but there should be significant differences--not just "the fangs are bigger" but "The head is narrower and more block shaped as opposed to the very pointed shape seen here. Also, while the build is stocky, the hindquarters are larger to assist the animal with climbing rock faces. The claws do not retract, and are heavy and sturdy--they are built for gripping, not slicing--unlike the animal pictured here, where the claws are built for shredding prey and enemies."
- Things that look like other things that have already been done -- Leaving aside the fact that it's kind of cheating, part of the joy of speculative evolution is seeing new and exciting creature concepts... not seeing the 46898th predator rat that fills the niche of a dog.
- Saber teeth -- They aren't actually that common. Actual saber teeth jut out, like in saber-toothed cats. Big long pointy teeth are common. Huge long pointy teeth are saber teeth, and are not common, as they are actually very fragile. There is convergent evolution--they've evolved six times--but they shouldn't be stuck on everything. Saber teeth are hypothesized to make creatures specialized towards large megafaunal prey, and even then they aren't necessary. Lions manage to take down large animals without saber teeth. Something similar to saber teeth can be seen in a few deer--water deer, for instance--but those aren't predators and don't use them for hunting, obviously. Also, they appear to be called 'tusks' in deer, but it seems to me to be a rather arbitrary distinction.
- Species -- Sometimes species get credit they shouldn't.
- Invasive species -- Invasive species are invasive because the native fauna and flora haven't evolved to deal with them yet. Given time, their advantage will be neutralized, except in a few extreme cases where everything is wiped out before they have time. Therefore, making projects with only invasive species is questionable, unless that's the concept, like in the excellent Terra Psidium.
- Predator rats -- Predator rats won't happen unless all competition is eliminated, because actual apex predators don't evolve from prey under normal circumstances. For instance, rats won't replace cats when cats are there. Most predators going extinct are apex predators, and rats would have to go through being mesopredators first. That means coyotes (Canis latrans) and domestic cats (Felis catus), to name the two species in the United States of America that we can't get rid of no matter how damn hard we try, would have to go extinct. If you're going to posit that, don't do a Dixon and hand-wave it with a sentence about how carnivore species don't historically last that long as an average; they don't last long because they get replaced by new carnivores species that are better adapted to specific ecosystems, and even then that's because a lot of carnivores are specialists--but not all current carnivores are.
- Whale-birds -- You know what one of the most successful air-breathing marine animals is? Pinnipeds. There are a lot of them, they are very common (Californian sea lions are reaching their carrying capacity in the USA.), and they are already fairly close to where the ancestors of whales were at one point. As far as whale-birds go, one would expect them to face steep competition from pinnipeds and remaining cetacean species. It's important to keep in mind that not all cetaceans are endangered, and many continue to thrive, especially smaller toothed whale species: Pantropical spotted dolphins (Stenella attenuata) have a population of three million, and are currently not declining.