Hi there
I cant really tell what exactly has gone wrong here... whether the bolt holding the assembely to the underbody has sheared or if the underbody itself was rusty causing the hole lot to come off.
Hopefully this should help you to understand what your looking at:
http://mb.braingears.com/126_DISC2/program/Chassis/35-040.pdf
Maybe someone with a little more experience can advise if this is a common fault.
Regards