If anyone is interested I found the following information about this Tetragnatha extensa.
Quote: The scientific name 'Tetragnatha' literally means four jaws, and these spiders do have some seriously large food processing utensils attached to their heads. The jaws (known as 'chelicerae') are hinged with the fangs at the tips, and when mating the male has to lock his jaws on the females to prevent her eating him.
When frightened Long-jawed Orb-weaver spiders lie flat out with their legs stretched out in a straight line. This allows them to hide behind thin vegetation.