There are only a limited number of people designing and illustrating their own worlds and life forms, and in quite a few cases their designs seem to converge on either similar biological designs, or on the work of earlier designers. In the first case 'convergence makes sense, as that is what evolutionary biology does as well. The second type makes less sense, if you ask me... Anyway, an example of convergence is that, if you wish to move quickly through water, streamlining is inescapable. There are many more constraints like that, and to be believable a design has too look biologically plausible.
But isn't that too limiting? Where are the limits in such designs? 'Cephalisation' is a recurrent trend in evolution, meaning animals tend to have heads, i.e., various organs and functions are clustered together near the front: food intake, sense organs and processing ability seem to form a package that comes with a discount if you buy all of them together. Can you do away with a head altogether?
How about limbs? I have discussed limbs and locomotion often enough in this blog and on my site that I will not repeat all that again: gravity and energy expenditure limit what you can do with legs. But there can be more or less than four. The current main group of Furahan terrestrial animals happens to have six, but rusps are quite common too, and some Giant Rusps, with 20 to 30 legs, give the hexapods a run for their money. And that does not even count the octapods or the five-limbed raptorial jumping spidrids.
Still, I do get the criticism sometimes that my organisms are too 'Earthy'. In part that is my own fault for having Furaha look so much like Earth. Perhaps I have shown too many parochial organisms. There are certainly some oddities in my sketchbooks that have not made it to the site.
One such follows: here are some arboreal predators; you might expect some lighting-quick brachiating animals jumping and swinging through the canopy, and these indeed exist (they're just not shown on the site either...). Instead, these are sneaky ambush-type predators, hidden in the canopy, preying on animals making their way over the forest floor. The one of the left might be descended from hexapodal stock, but the one on the right has a body plan all its own. As you can see, the predators can grip branches and can spear animals passing underneath. If that doesn't kill them, their poison will, and rather quickly to (it had better, or else the wounded animal will bound away and succumb somewhere beyond the predator's reach.
But is this believable? Is such an essentially passive and sessile life style workable? Wouldn't prey learn to spot it and simply choose another path? Isn't this an evolutionary dead end if the prey has good senses and is highly mobile? Personally, I am not certain, and so this particular type of predator is even more imaginary than the rest of them: I haven't decided whether to raise it to the rank of actual Furahan species or to condemn it to continual 'uncreation'.
I would like to ask the readers of this blog to comment on two sketches of plants (or mixomorphs, as the case might be). I did have a specific environment in mind, but would like to hear your opinion. Both are 1-3 meters in heigth. Species A is round with branches coming out of whorls on its body/stem, and species B is flattened sideways, and seems to sit on the ground rather than grow from it as species A does.
So, are these not alien enough, or are they too unlikely to be believable?