Murdalok

I have doubts that hes a purebred, because he wouldn't have been given up like he was if that was the case. My nephew said Dexter's previous owner claimed that Dex's dad was a military working dog, which in almost all cases are Belgian Malinois or GSDs. I told the vet he was probably mixed, and he said if he was he doesn't see it. As far as his ears they may just stay floppy, but I've been told they can pop up later in his life. My sister in law has a Malamute/Husky mix with floppy ears.

This is Dexter James [ATTACH]65745[/ATTACH] We got him via my Inlaws from a friend who couldn't take care of him. I took him to my vet the morning after we took him home, to get his initial vaccinations and a checkup. The vet said he was perfectly healthy. This where my question comes in. My inlaws claimed that dexter is 10 weeks old. At the vet he weighed in at 8 pounds. Is it just me or is he really small for that age? Most info I could find says he should weigh around 20 pounds at 12 weeks. Here is a picture of Dexter playing with one of my Chihuahua Rat terrier mixes. She is 13 pounds. [ATTACH]65746[/ATTACH] Should I be worried? Don't get me wrong, I will love and care for him no matter what. Just curious.