Actually, Frank Welker and Jim Cummings would be considered returning cast members. Frank Welker voiced the Spinosaurus in LBT XII, and Jim Cummings voiced Sierra in LBT VII. As for the new cast, I came up with a possible explanation today

. The Gang are most likely aound ten to twelve years of age, right? After recently reading a post on the GOF regarding Aria Curzon's voice deepening throughout the series due to puberty, I think I figured it out: the voice cast is aging

. The voice never stops aging as long as the body continues to age, and the cast of twenty and thirty-somethings that have portrayed the Gang for the last decade are losing their abilities to continue to sound childlike as time passes

. I've even noticed over the years that Cera's voice sounds like it has aged

. So, why not bring in some new actors who really are ten to twelve years of age and keep the Gang sounding like ten to twelve years of age? That would be the wise thing for Universal to do, rather than havin' folks aged twenty and over try to portray ten to twelve year-olds

. That'd be like those "teen" movies in which actors who are twenty-five and older play high school-aged folks

:

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