I went through the bug reports but, (hopefully), am not repeating this in a bug report I missed. 

A friend and I bred our two tyrannies together.  I waited the appropriate 3 days, turned in the ticket and, to my surprise, received a Great Dragon baby, not a tyrannosaurus baby. 

I know tyrannies are considered in the GD class, which is written most prominently on the first line of the description when pet is shrunken but I much prefer the body size of the tyrannie for boating/fishing--and it still has the nice benefit of the GD's skills and stats.

I did read the wiki of animal breeding to see if the above result is possible or normal but didn't see anything written there.

The little t-rex is the same as a greater dragon, it was just reskinned, they were for an event and not really meant to breed, but the dragon is the correct baby

But they have so much more use as a T-Rex!  I do wish there was more to Jurasic Park than there is currently.  Imagine the fun and games and tribes of canablistic headhunter frenzied Ostard Riders chasing players through the plains and paths in a jungle!  Make me use bolo balls and dismount the players as they try to run away, then have them casting Druid spells to entangle and stone circle the fleeing players

Yes I did have a big event that I made with XML spawner, but it really needs hard code.  I will try and bring it all back when I have time ty

Thank you for the clarification...I'll pass info on to my friend who also got a GD today when she turned in her ticket.  As I stated in my post, the only reason I preferred the T-rex is because of its smaller size, great for boats/fishing.