There is no "CMU Museum of Natural History" in Mount Pleasant, Michigan. The inquiry likely confuses two institutions:
Location: Pittsburgh, Pennsylvania (Oakland neighborhood)
Phone: 412-622-3131
Affiliation: Carnegie Museums of Pittsburgh (founded 1895 by Andrew Carnegie)
CMU's campus in Mount Pleasant houses the Museum of Cultural and Natural History (Brooks Hall), focusing on Great Lakes archaeology, anthropology, and natural history. Contact: 989-774-3829.
The Carnegie Museum is world-renowned for dinosaurs (Diplodocus carnegii), minerals, Egyptology, and wildlife dioramas. CMU's museum is a regional university collection. Different institutions, different states, different collections.
Verify which institution you intend to contact before calling.