So why bring this up? Because I am working on a painting of a 'secondary lateralised spidrid'. It's a small exoskeletal predator. Think of a jumping spider on Earth. The animal is descended from radially symmetrical spidrids, and during its evolution the new plane of symmetry somehow came to run through two opposite pairs, rather than between them. Mind you, these exist too, but for unknown reasons the latter group is almost exclusively herbivorous, while the ones with one jumping leg are mostly predators.
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| Click to enlarge; copyright Gert van Dijk |
So here is a colour sketch. I think I will call it a 'prigoon', but I haven't thought of its binomen yet. The name will probably contain 'dougalii' or 'dixoni', as Dougal Dixon was the first to come up with this odd arrangement, and I wouldn't want people to think I am quoting anything without a proper reference.
31 comments:
I do remember you mentioning furaha having 5 legged animals, though mostly because I was curious how you'd fit them into the established biology of the planet.
Keavan: I can't realy remember having said that. If I did, I was probably thinking over radial symmetry, or perhaps of cheating, linke with the prigoon.
How would an odd numbered limbs evolve in a bilaterally symmetrical creature? The only idea that kind of makes sense is a biped or quadruped modifying its tail into a third/fifth walking limb but what about those with an unpaired front leg? A modified sternum-analogue perhaps?
perhaps the part of the body that has the limbs, remains radial longer than the rest of the body (which is what I wondered when I first heard of the 7-armed octopus (actual species, yes)
or maybe its just not derived from the same stuff as the true limbs - like spider monkeys' tails...or it just looks like one, like I read once in a zoo book "look, teacher, the rhino has five legs!"
-rodlox
Bardelot: An odd number of limbs starting with bilateral symmetry... I agree that a medain structure makes sense. in a way, the kangaroo does exactly that: https://planetfuraha.blogspot.com/2009/10/odd-walkers.html
By the way: that post already contains a skecth of what has now become the prigoon. As for a frontal unpaired walking limb, heads are usually in front, but I cannot imagine animals starting to use their heads fro locomotion. but if the animal already has something mova]ble sticking out in front, that could perhaps be recruited for walking. A tentacle perhaps? But the original purpose would be lost, so that is an additional difficulty.
Rodlox: That is my approach as well: start from a body structure, not from legs.
Random question: If a hexapod were to evolve wings, would it make sense for the front or the middle pair to become the wings?
Neat little design for a creature. The name "prigoon" is a strange-sounding one too, I'd like to think that it's named after the sound it makes? "PRRRRI-GOOOON! PRRRI-GOOOON!" (Do Furaha spidrids vocalize or stridulate in any way?)
to quote from _El Dorado_..."Both? Both. Both!" (in answer to the wings question)
-rodlox
Since that fifth leg is technically unnecessary for locomotion, could you have clades where it becomes so specialized that it's only used for jumping, or even where it atrophies or even disappears?
KLB... and others: sSorry about the late reply; I was too busy first and then away without access.
KLB...: there is at present one group of hexapods with wings; they use both the first and second pairs of legs as wings. The result is that they have four wings. They are called tetrapterates, not to be confused with tetrapters (those are the radial ones).
I guess the choice of limbs to turn into wings would have to do with all a hexapod would take to the air. Running or jumping from branches seem likely. For running, the part with wings will tend to be lifted up while the rest is still propelling the animal. If the hind end is lifted, the animal might stumble forwards. I guess the first or second pairs are more likely to turn into wings. The second pair may have advantages: 1. it is likely to lie above the centre of gravity, so would induce no awkward tilting effects; 2. it leaves the hind legs to start the flight; 3. it leaves the front legs as shock absorbers for landing.
Perhaps I should add such 'dipterates' to the Furahan meangerie. No doubt they would quickly be called 'dragons'.
Sonic... Are you the same person with a different odd name every time? Could you please wind that down a bit? ;-)
The name ‘prigoon’ was derived from the Russian word for jumping. But I like the sound effects.
Rodlox: Both indeed! There are already tetrapterates.
Evan: Welcome back! In prigoons and their relatives, the jumping leg is also used for slow walks. That is actually quite complicated, because the jumping legs makes steps that are twice as long as the steps of the other legs, and it takes double the time. So part of its step is in synchrony with half of the other legs (if the jumping leg is 3, the other walking legs are 1,2 on one side and 4,5 on the other). So 3 moves with 1 and 4 for the first art of its stride and with 2 and 5 for the other.
I guess leg #3 could atrophy or turn into a stinger or something else, but what a pity...
To follow up on the "winged hexapod" idea though, what would a transitional form for a creature with middle-limb wings be? How would centaurism work for middle limbs to be the precursor of wings, would it make sense for a six legged creature to have its middle legs become arms while walking on its front and hind legs, before becoming wings?
hajnarus: that is indeed not an easy transition indeed. I like the idea of having the middle limbs become armns first, but a problem with that is that transforming the first pair of legs into arms would probably work much better (centaurism). How about the following: a hexapod creatire thros itself from a branch and spreads all six limbs to fall slower. The legs develop wing membranes or feathers or someting else to help with this. However, the aniomal hasd to land too, and over time the conflicting demands of catching air, landing and walking result in specialistaion of the limbs.
How many different "phylums" of creatures are there on Furaha? There's the vertebrate-analog hexapods and the arthropod-analog spidrids, I wonder what else is there. Would be really interested to see a Furaha cladogram at some point!
perhaps the mid-limbs are used for display or feeling its way around, while the fore- and hind-limbs are for locomotion (centaurism is avoided by having a heavy or large skull?)...and then it starts climbing trees and using the mid-limbs to parachute or otherwise slow/lengthen its descent, with the other four legs used to grip and land with.
-Anthony, aka Rodlox.
^: hexapods are like vertebrates with a similar amount of subdivisions. Otherwise there are kwals, wadudu, spidrids, rusps, tetrapters, wardens, at the very least, for animals that is. I will one day make a cladogram, but that is not very useful right now as the number is verey likely to change. I imagine there are a few dozen of worm-analogues at any case.
Anthony: another nice approach to the problem!
thank you.
*google searches for Wardens* no results found. *shrugs* one more clade of creatures to eagerly await for.
-Anthony
nevermind, I was googling with the main page, not the blog.
-anthony
Have you already featured the Serina project on this blog? Happened upon it a while back and it's a neat little work of speculative evolution, I'd love to see your opinions on its outlandish creatures and how plausible you think they are.
Particularly, there's one group of creatures called "tribbetheres", which are descended from terrestrial ray-finned fish and evolved into tripedal mammal-analogues. I wonder about the anatomical plausibility of these creatures and the structure of their limbs (also how uncannily mammal-like they become, right down to fur and external ear pinnae).
Another creature of interest would be the "ornimorph", a highly-specialized bird that lays amphibian-like eggs in water, which hatch into aquatic tadpole-like larvae that gradually climb up onto land, become terrestrial juveniles, then climb up into the trees to become arboreal hunters, then gliders and eventually true flyers as their feathers grow in, practically re-enacting the entire history of tetrapod evolution over the life of a single individual undergoing a dramatic metamorphosis.
Would be neat to see you take on this project sometime!
Anthony:
As for clades, I forgot the cloakfish. There are at present four spreads (i.e. two pages each) devoted to Wardens, with the following species: phleph, flachkopf, snigel and cthulhu. The phleph was shown once in its old oil painting form. It evolved considerably since then. And you can find a Cthulhoid carapace on the blog too...
I will have a look at the Serine project. I admit I have not been following other projects closely for some time now, but it might be nicve to discuss other projects again, provided thay are interting and well illustrated. I just had a quick look. They fit the bill. The tribbethere legs indeed seem to be very mammalian, but I know from my own experience that it is very difficult to escape falling into the 'just draw a mammal leg' trap. I am still slowly programming a leg movement rtoutine hat should solve that.
Personally when trying to draw an "alien-looking" quadrupedal creature I like giving them backwards legs shaped somewhat like a grasshopper's to avoid the "mammal leg" cliche. Not really sure though how well that would work for any animal larger than a cat...
'Winged': Search the blog for 'zigzag' or 'legs' and you will find considerations on that subject. The real question is whether 'zigzagzig' legs make as much sense as 'zagzigzag' legs. And yes, that sentence may make sense after reading the specific blog posts...
could it be possible for tripods, quadrupeds and hexapods to all arise simultaneously from fish like ancestors and then they compete a lot at first but eventually settle on separate niches and all continue to exist? or would one of the three invariably be the most efficient and quickly drive all the rest to extinction?
Provided the legs of these 'X-podes' do what they are supposed to, i.e. to get animals around, with comparable efficiency and speed, I cannot see why their number should matter.
Anonymous -
I could picture each of the X-podes having an advantage over the other groups (tripods with better breathing abilities, but hexapods having superior jaws or locomotion, etc)...so each group could trudge onwards til a Permian-style extinction decides the matter.
-Anthony.
Anthony: that is certainly possible. In fact, superoroity in one aspect goes weel togetrher with my criterion of similar locomotor ability.
on the topic of two-winged hexapods, i was thinking of a hexapod dubbed a "geckogriff", which starts life as an arboreal gecko-like hunter, whose middle legs are splayed out wider and have hook like thumb claws, and broad pads on the rest of the digits, in order to aid in climbing.
as it grows it becomes more agile at jumping and later gliding, as the finger pads of its middle legs become longer and wider and somewhat similar to a bird's primary wing feathers, and once it becomes adult it's an active flyer and an airborne predator akin to a hawk, with membranous wings wit individual "feather fingers", that rarely lands except to lay its eggs among the top branches of trees.
the gecko-like hatchlings immediately scurry for cover upon birth into dense foliage, which is difficult to reach by the many flying predators (including other adult geckogriffs) and live in the canopy until their wings are developed enough to fly.
Cuddledee: That sounds like a further stage of what I wrote above: a hexapod creature throws itself from a branch and spreads all six limbs to fall slower. The legs develop wing membranes or feathers or someting else to help with this. However, the animal has to land too, and over time the conflicting demands of catching air, landing and walking result in specialisation of the limbs.
So that scheme started with all six limbs starting with multiple functions including 'parachuting', and yours with just the middle limbs, if I understand it correctly.
spec evo wise do aquatic bats make sense or are they too specialized for flying
Battypus: Aquatic bats... It all depends what you want, I would say. The question really needs more focus. Also, you might consider the Speculative Evolution forum for such questions. I recently had time to answer questions not related to Furaha or its 'Allied Matters', but will probably have to limit that...
//I cannot imagine that anyone will remember that I wrote about animals that walk on five legs in this blog
I remember. I also remember you promising to explain why toes are important and I'm still waiting on that.
Andrew Broeker: Hiow nice of you to respond. i certainly remeber that promise, and though it has not yet been fulfilled, it has not been forgotten. I have a stack of pdfs in a folder called 'toes' that I have ditifully transported to a new PC. it contains several paers on various aspects of legs, including toes. I will write that post.
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