I think I've got the mileage credit part understood, but I earn my elite staus via segments, not miles, so...

Suppose I fly IAH-MSP R/T and the IAH-MSP is nonstop on CO, I get one credit, assuming I book on CO.com or the eligible fare class. However, if the return is MSP-MEM-IAH on NW (CO codeshare) do I receive two segment credits on CO - again assuming I meet the criteria for getting segment credits on CO? Thanks.