Yelinak and Zlandicar are both identical to the Velious Dragons (twisted neck) but if you look at them closely in graphic 184, you'll notice texture 3 (I believe.. should be white/Yelinak-ish) has a white body, just like him, but has a gray head. Zlandicar, texture 4 if I am not mistaken, has the correct legs and tail color/graphic, but head, body, and wings are off.
So I guess VI gave up and just gave them a new model. 195 are designated for Yelinak and Zlandicar. There's only two textures... and they have correct color scheme.
As for making dragons sit, I don't know if there is a way to spawn them as sitting, but once they're up, I think there is probably an #appearance command to make them sit (I don't mess with that, it usually kills me...) ... but if you wanna do a quick test and see if something has a sitting animation (some things do.. dragons, mermaids, some humanoids...), use the command
#doanim 33
Anyhow, think that's all.

Best of luck! :P