Did you make sure to get the Old Amber (Aerodactyl) from Glittering Cave? At least I found mine there using the dowsing machine.

Oh My God! that fits so well! :lol

Nope!
I'm missing all the fossils sans the latest 2 :p

Pokemon left to complete the Kalos dex.
Pyroar
Floette
Florges
Gogoat
Pangoro
Aromatisse and her pre evolved form
Barbaracle
Dragalge
Clawitzer
Tyrantrum
Aurorus
Goodra
Noivern
Yveltall.

Can someone tell me what I'm doing wrong? I've beaten the Elite 4 and caught both Mewtwo and Zygarde. What have I not done to trigger the other Mega Stones to appear? I'm even following the 8-9 and 9-10 pm stipulations (I've seen sources citing both times), but I can't get any of the post game Mega stones...

It's 8-9. You already met with Sycamore to discuss the mega stones in Anistar City, right?

I guess not :I

Well yeah, I think you have to do your rival battle in Kiloude first, then she/he mentions the Professor wants to meet you or something. Then you meet at the large crystal structure in Anistar and then the event triggers, allowing you to see the Mega Stones' shine when you go to their locations

On the Elite Four...the first 3 only gave me some trouble, but dang! Chef Guy's Gyarados!

So, the Helix and Dome fossils are Y only. Can someone help a brother out?
I also can't find a Skull fossil...Plenty of flipping Root Fossils, but no Skull Fossil...