Dragonnel, Wyvern, & Dragon Turtle: Wyrmling-Great Wyrm

[Wolf72]

Rough CR's ... very rough

I'll start with the dragon turtle, at 12 HD the MM has it listed with CR 9. I'd go and give a hatchling CR 2, mostly because of it's high AC and breath weapon.

HD 1, CR 2
HD 2, CR 3
HD 3, CR 3
HD 4, CR 4
HD 4, CR 4
HD 5, CR 4
HD 6, CR 5
HD 7, CR 5
HD 8, CR 6
HD 9, CR 7
HD 10, CR 8
HD 11, CR 8
HD 12, CR 9 (official)

Wyverns are CR 6 at 7 HD, they're not that tough but they have a nasty sting. Hatchlings I'd put at CR 1.

HD 1, CR 1
HD 2, CR 1
HD 3, CR 2
HD 4, CR 3
HD 5, CR 4
HD 6, CR 5
HD 7, CR 6 (official)
HD 8, CR 7
HD 9, CR 7
HD 10, CR 7
HD 11, CR 8
HD 12, CR 8 (I think a Dragon Turtle would kick the stuffing out of a Wyvern, even at this HD/size)

Dragonnel's are a little tougher, they have no real special abilities except flight and some decent combat options (jump + crush = ouch)

HD 1, CR 1/2
HD 2, CR 1
HD 3, CR 1
HD 4, CR 2
HD 5, CR 3
HD 6, CR 3
HD 7, CR 4
HD 8, CR 6 (ToH has it listed as CR 6, for a Huge beast)
HD 9, CR 6
HD 10, CR 7
HD 11, CR 7
HD 12, CR 7

I'd reccomend anyone useing these CR's check them against similiar CR's and see how they fair.