I've been reading the supplement Dragons Revisited and noticed the Metalic Dragons all have references to an alternate form power in their description, though only the Bronze, Gold, and Silver sample dragons have the ability in their stat blocks. Looking at the Bestiary and its errata there isn't any mention of an alternate form for any of the true dragons.
Due all true metallic dragons have an alternate form? If so what age do they receive it at and where is the source material?