shell is a part of a mussel & a freshwater mussel is a kind of mussel ->  shell  is a part of a freshwater mussel  shell  is a part of a freshwater mussel & fossils of shells of freshwater mussels are found in a mountain range ->  fossils of freshwater mussels are found in the mountain range  fossils of freshwater mussels are found in the mountain range & if fossils of a water animal or plant are found in a place then that animal or plant used to live in that place & a mountain range is a kind of place & a mussel is a kind of water animal ->  the freshwater mussels used to live in the place where the mountain range is located  a freshwater mussel is a mussel lives in freshwater & a mussel is a kind of water animal ->  a freshwater mussel is a kind of water animal that lives in freshwater  the freshwater mussels used to live in the place where the mountain range is located & a freshwater mussel is a kind of water animal that lives in freshwater ->  the mountain range used to be covered by freshwater  the mountain range used to be covered by freshwater & a river usually contains freshwater -> the mountain range was likely to be covered by a river