So, (while I have a few minutes to wax nostalgic during unattended office hours/dead time before I give an evening exam) a few bits of (possibly) relevant information:
1) The picture at the beginning of this thread
never had a canonical head. (Where that image appears in the lore document, it is explicitly noted that the head has... issues)
The picture from the wiki is the result of the following sequence of events
a) Artist draws picture of Aera that is (except for head) relatively in-line with what we were looking for (certainly better than most previous attempts).
b) Artist is referred to description of Aeran jaw hinging being reversed (top is mobile, bottom is fixed)
c) Artist flips existing head upside down (in photoshop? redrawn? It's been too long) and reattaches it.
d) Canonical head is never re-drawn in time between this image and artist moving on.
e) With notation that head is non-canonical, image remains best rendering of Aeran body plan (in off-line lore document).
f) Notation that head is not canonical doesn't make it into the wiki.
<some years pass>
g) this thread correctly notes that the head has some (probable) biological plausibility issues, but information is not available that this is, let's say, a known bug due to non-spec implementation
2) To help clarify, to the degree possible via quickly written text, the original intentions:
a) The eyes are, among (several) other things, closer to the brain case than depicted - i.e. much further back in the head, not at all near the end of the elongated mouthparts.
b) The elongated mouth section is noticeably narrower than the head (for inspiration, consider the Gharial, but not nearly as extreme, especially in elongation), and the jaw hinge is somewhat further forward with respect to the skull than on a human skull (or that of the aforementioned Gharial). The mouth section is also not as thick as the skull vertically.
c) (Just the completely clear) The eyes are not on either part of the jaw. The eye(turret)s are on the non-mobile portion of the skull, above, behind, and to the sides of the jaw
d) Aeran eyes are i) widely set ii) turretted. (Consider chameleons for inspiration for the latter). Like terrestrial vertebrate visual hunters, there is a keenly defined stereoscopic visual field when the turrets are at their forwardmost facing. At the same time, independent tracking to their sidemost positions allows a large total visual field reflecting the fact that the line that eventually produced the Aera spent much of its development in positions other than the top of the food chain on their homeworld.
e) Aera have lips, but the lips have progressively less flexibility and greater durability the further toward the end of the mouth they go. The converse is also true - the back corners of the mouth are quite flexible and expressive
f) Aera do not have nasal openings distinct from the oral opening. Chemosense (i.e. smell) is primarily achieved via smell-sensitive regions at the protruding and flexible back corners of the mouth, and assisted by less sensitive chemosensory receptors on the nearby throat regions. These openings are the primary means of respiration during sessile periods. When more active, the mouth as a whole may open to some degree to increase airflow. As one commenter long ago once intoned "so they can't breathe and drink water at the same time?" - Yup. Just like a person with a clogged up nose (except they still can smell just fine).
3) Misc
a) The Aeran chlorophyll analogue is closer to yellow than green, affecting associated Aeran coloration considerations
b) The jungle floor/near floor, where the Aeran line developed, is relatively dark if the canopy is thick (it was). This influences the pervasive muting of Aeran (non-display) colors. Or, to put it differently, to the degree that their body patterns were camoflauge resembling the surrounding environment (which they were, but not completely), they looked more like mulch, tree trunks, exposed/travelling roots, old-growth branches, and sparse undergrowth than like leafy vegetation in the upper canopy.
c) Aerans are not scale-covered (more toward the "leathery hide") end of things.
4)Cross thread questioning
How do the Aera age?
Are there subspecies/races/ethnicities and other mophic variations?
What about different sexes? pathogenic (one sex, born pregnant)?
Do they lay eggs like Terran reptiles? or live birth?
a) Quickly, and, later, in old age (late 20s onward), painfully :/ More seriously, they go through no profoundly metamorphic phase, if that's what you were asking.
b) Subspecies, no. Races/ethnicities yes, but not that we, as humans, would necessarily key in on visually (recall the biological definition of race -> "shared trait" -> all people with attached earlobes are a "race"). Feel free to do something subtle to indicate greater diversity than "single-biome planet of hats" (the Aera's ancestors started in a single biome on a single continent, the planet, not so much.... even after they burned down the forests, it's just bio-simple, not bio uniform -- but I digress ) but I'd avoid making it "purple Aera vs. grey Aera".
c) Nominally two genders.
d) Can't honestly remember if I ever decided this. Compared to humans, they do have a reproduction strategy involving larger numbers of offspring per mating, but I can't recall if it was eggs. I think it wasn't, but I could be misremembering.
Hope that was useful to someone (if a couple years late for the original thread poster)