If brain size and intellectual abilities were correlated, dolphins would be much more intelligent than humans.
Believe me, they are not.
The average bottlenosed dolphin, displaying some of the most brutal social behaviour amongst cetaceans (and yes, its the "flipper" species), will find his match with an average 4 yr old kid. Which is all fine and well, but unless you just WANT to believe, there is not really much about it.

Likewise, some anomaly in skull size - untill otherwise proven - means that it was an anomaly, probably caused by a genetic defect.