Clam/oyster from West Papua

Can any of you guys help me correctly identify this guy?

Taken in the Raja Ampat islands of West Papua Indonesia

Looks like a type of Spondylus, or Thorny oyster. Perhaps Spondylus squamosus. Coral Reef Animals of the Indo-Pacific states it "can be recognized by its grey mantle with black lines", and that "the shell has white spines with black markings on the inner side and basally". Its range includes PNG and Indonesia, so it's a possibility.

I'm not so sure it is. There are none of the lines on the mantle. However it does have the thorny protrusions.

In terms of size it was about 12 inches across.