Are we even sure that there are front and rear legs? Couldn't they have three legs sitting side by side? That way Idirans could sit down on chairs just like (wide) humans.
Some other random thoughts and observations - when Xoxarle gets hit by Horza's fire: "The air glowed with laser fire as he dived for the first side tunnel; the wall blew out at him, and something hit his leg and back." And a bit later: "His keratinous back plates were almost burnt through where the Changer had shot him, and his leg was hit, too, slowing him all the time."
A single leg gets hit when shot from behind, and the leg apparently warrants no further specification. This could lead one to believe there is only one back leg.
On the other hand, when Xoxarle is carrying Balveda on his back, she tries to kick him in the knees (plural). This seems to indicate there are two backward pointing knees.
But then again Xoxarle breaks Balveda's arm across his thigh: "He brought one knee out, holding his thigh level with the cavern floor...". This sounds like there are several knees to choose from; if there was only one possible knee to bring out that way (i.e. the knee of a single front leg), then one would rather expect a phrasing like "he brought his knee out".
So that's a bunch of rather weak and contradictory conclusions, obviously.
We do learn though that an Idiran can stand reasonably well on only two legs, which I think is significant. This can be troublesome for tripedal designs, and "wide" Idirans like those in the pictures posted by Deep Black would need to do some serious weight shifting contortions to avoid falling over. And maybe they do just that, though I would prefer a narrower configuration where the natural position of the thighs is more vertical.
Speaking of thighs and such, going by the words used the structure of a single Idiran leg seems to be similar to that of a human, i.e. thigh, knee, lower leg, ankle, feet/toes. There is no mentioning of additional joints and segments as far as I can tell.
Last edited by Coral Beach; 05-03-2013 at 05:40 PM. Reason: typo
Something else, Andrew J Short felt that six eyes would be appropriate for an Idiran, I'm inclined to agree particularly with reference to the point you make about the vestigial arm.
Genuine question do you get the impression that while Idirans move forward in one direction, they've evolved from an animal that was omnidirectional?
Drink, but very carefully...
& I was picturing Rolf Harris as an Idiran:
"Just have fun"
Perhaps Idirans have very flexible waists, allowing their upper body to face forwards over a wide range of movement- possibly an entire semicircle, or even more; this would allow them to sometimes have one leg in front, sometimes two. Something like the way an owl can turn it's head round in a nearly complete circle.
I can imagine a chair incorporating a back support, to suit a rear 3rd leg. It would be asymmetrical, the support would have to cantilever from one side and the sitter would have to maneuver in sideways from the other side. I don't know if that helps the discussion though.
On second thoughts your Idiran chair could be a memoryform, and the back support would move into place as the sitter sits. IMB does not say that Idirans have morphing furniture, however a civ capable of taking on the culture must possess some high tech.