I'm basing that on research we've been doing on the Asian natricines. Rhabdophis species are well documented to cause extremely severe or potentially lethal bites. Yet, when we got them in we were quite suprised that the venom yield wasn't huge and the teeth weren't particularly massive. This got me concerned that very closely related genera may be hiding potentially lethal species. Macropisthodon is awfully closely related (used to be in the same genus) and the teeth are much more well developed. Thus, I am extremely leary of them. We are hopefully getting in some in a couple weeks to confirm things. I expect that we'll show that it has the same potent disruption of blood clotting as Rhabodphis does.