One afternoon last week, while visiting his father in Seahaven, Sam Hudson came upon a prehistoric-looking creature moving across the road. It resembled a small boulder, except for its beady black eyes, puckered mouth and skin sagging into crepey pleats. Its domed shell was like petrified wood, and each hexagonal scute was a weathered sandy brown. Mr. Hudson wasn’t sure what he was looking at—wild thing or wayward pet? “My first thought was, ‘Has this…