is this a dog or a lion ?

Tibetan Mastiff An impressively large dog with noble
bearing, the Tibetan Mastiff is an aloof
and watchful guardian breed. They are
extremely independent and intelligent. The origins of the Tibetan Mastiff are
somewhat murky, but earliest written
accounts place a large dog around 1100
BC in China. The breed remained
isolated in the Himalayan mountains,
where it developed into the Tibetan Mastiff we know today. Primarily a
family and property guardian, the breed
was traditionally kept confined during
the day, then let loose at night. They
were left behind to guard the tents and
families when the flocks were moved to higher pasture.