I agree with you, it is unclear where and when these prizes will drop.
- Glimmer Raptor: This is clear for this one: Final prize of the event. Should drop when we collect 1000 Dino Eggs
- Baby Dino: It is said "Final prize of the event". May be the mysterious egg will hatch (at level 6) and the baby dino will drop... but it is unclear
- Sabertooth and Gnomeanderthal: I strongly suspect these will be part of next week's monster hunt and leaderboard 1st and 2nd prizes.
if we go back to the previous Atrium kind of event (Off the walrus - April 28), it was quickly followed by a MH/LB event (May 5), and the Tadpole Kelpie mentioned as prize in the first week, ended up being the leaderboard prize of the following event...
Sources:
Off the Walrus - April 28 :
https://forums.storm8.com/showthread...ghlight=atrium
Monster Hunt s40 & LB - May 5 :
https://forums.storm8.com/showthread...t=Monster+Hunt
It's a shame, cause the only interesting prize (at least for me) is the Sabertooth, but will probably come during the MH/LB event...