The tail end of the keel is embedded deep into the underblock. The four holes are for ezlaser bypasses.
The keel itself functions as a large damper but even so it is still enclosed in a further damper here.
The protrusions on the pelvis act as attachment and bracing points for the power cylinders.
The joint between the underblock and the thigh bone is essentially built for free movement. Hydraulic dampers are built-in, but the joint is unpowered. Movement is accomplished by the power cylinders described in the next section.
The one piece that looks like it could be built as a single block, it is of course partitioned to withstand shock and allow the greatest margin of movement.