at our store in the pet department we have "mammoth bones" I'm assuming those are marrow bones? Once the dogs get the ends gnawed off theres soft white stuff on the inside. I haven't gotten any lately because the vet said 'no more body parts' for Happy because of his weight and he says they will shred up a dogs tummy, but I'm thinking getting them and letting them have them in the evening for their crates. Might help mister stubborn (Sam-wise) adjust to his crate faster. Can the marrows hurt their tummies? He didn't say Lucky couldn't have one, he put Happy on a no body parts diet because he was throwing up really bad for a couple of days (which was probably because of those rings in his tummy!) and he's 10-15lbs over weight. No canned food, no treats, no nothing cept four cups of dog food a day. Happy is a chewer too, and though he'll chew on the nylabones you can tell he really misses his mammoth bones.