Abby, you have noble roots
Abby, you are no mere mutt. You are definitely Catahoula leopard dog, not Aussie. The head that is too large for the body is breed standard. I bet you have webbed feet and can outrun and outmanuver any dog you meet, even in mud where other dogs slip and slide.
Catahoulas were bred to work in the swamps of Louisiana. Look up "patchwork Catahoula" in Google and you will see some dogs who look just like you. And they are highly prized as beautiful specimens of the Catahoula breed.
Liz and Gumbo (a red leopard Catahoula mix)
http://images3.fotopic.net/?iid=yya0...ze=1&nostamp=1
(Liz can't figure out how to make the image show up, so click the link to see my picture -Gumbo)