I found this skull on the grass on the side of the property that fronts onto a road. As far as I could see, there were no other bones in the vicinity, suggesting that the rest of it had been carted off for food. Or maybe the head had been carted off to our place by a predator.
Perhaps surprisingly, with all of the bushland and creatures such as dogs, cats and foxes hanging around, I don’t find many bones – this skull is an exception. I don’t know enough about the skeletal structure of various animals, so I have no idea what it is. While I didn’t measure it, my guess is that it was approximately 15cm to 20 cm long, and it seems that a part of the jaw has been broken and is pointing at 90 degrees from the rest.
If anyone can tell me what it is, I’d be grateful.
Fifteen Acres 
I checked in Babara Triggs’ “Mammal Tracks and Signs” and it looks like an Eastern Grey Kangaroo skull. This book does not have a side-on diagram of a Black (Swamp) Wallbaby but the overhead view seems shorter and more tapered.
Thanks John. That’s sad if it is a kangaroo. There have been a few killed by cars recently, at best it is one of those. If it did turn out to be a Swamp Wallaby, it could be the joey that ran into the bush when the female drowned. Thanks so much for going to the trouble of looking it up. I appreciate you doing this. Lisa