Recently, Amy Breschini from the Farm Advisor's Office sent over  these photos.  What an amazingly perfect specimen example of this type of mushroom. 

"We had a rancher (from Paso West Side- near the lakes) send us a picture of these crazy mushrooms growing on Live Oaks and I looked it up..."
After a little research, here is what she found:
"I believe it is Hericium erinaceus which has several common names:  "lions mane", "monkey head", "bearded tooth".  One reference said that there are seven different genuses in which have the same “toothed” appearances.  It is also found in the Bay area, and can be found on American Beech trees."

As with most mushrooms, there are species with look-a-likes, so assume it's poisonous, unless you have an experienced mycologist with you for proper identification.

Here's some photos from Berkeley : http://calphotos.berkeley.edu/cgi/img_query?stat=BROWSE&query_src=photos_fungi_sci&where-genre=Fungi&where-taxon=Hericium+erinaceus&title_tag=Hericium+erinaceus

Thanks Amy for supplying all of us with this great Topic!