If by ‘contiguous’ you mean as the original ‘paired shells‘, the answer is yes. However, this is most common for burrowing species. For surface dwelling species it is the exception that the two valves stay together upon death. For burrowing species it is quite common.

Thank you very much for the information. it's now more clear for me.

Best regards.

Contiguous (if you mean articulated shells) this happen when the species lives in the ifaunal mode and this is gives an protection for them from the post mortem process and hence have a better opertunity to be arrticulated.

Dear Dhouha Salmouna,

These oysters (Ostrea olisiponensis, O. delettrei, Lopha sp.) joint valves can be preserved in particular post-mortem environmental conditions : a) absence of current able of separating the valves which are initially joined by ligament tissue, b) a very high sedimentation rate allowing very rapid burial (just after their death) of these benthic organisms.

Best wishes