Secondary patterns of palaeobiogeography are of importance in recognizing provinciality.In Greenland

which is representative of the Boreal Bivalve Province

bivalve endemism increased from the late Middle Jurassic onwards and reached the maximum by the Oxfordian.Morocco belongs to the Mediterranean Bivalve Province with the most distinctive endemism during the Early Jurassic.For temporal changes in diversity

three cycles can be recognized and the Kimmeridgian marks the diversity peak.For spatial changes

the highest diversity occurs in southern England and northern France

and from there the diversity shows a northward and southward reduction.