What is head splitting / skull splitting? And when does it happen in the Dogue De Bordeaux breed?

We were at group training class and the trainer asked "How old is he now?" then followed with "Oh, his head should be splitting soon." What is head…

ASKED BY Empereur on 4/16/14
TAGGED split, splitting, skull, head, growth, widen, broaden IN Dogue de Bordeaux

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