Is there such a thing as a bone cleaver?
Absolutely.

I have this one here: J.A. Henckels International Classic 6-inch Cleaver   ... it is billed as being designed "for chopping through joints and bones". These cleavers tend to have good, solid weight and a short blade bevel to give it endurance and power. You would not slice things with this. This is a momentum tool to crash through the target tissues with a confident swing. The hacksaw that you mention offers better control, in general.

The opposite of this is an Asian style cleaver that is used primarily for vegetables. Lighter, faster blade with a deeper bevel which makes it sharper for slicing but it would wear down faster under the impact of bones/joints.