Karen Sears Laboratory
Funded by the NSF
This image was produced as part of a project that focuses on a crucial, yet often overlooked, aspect of the evolutionary transition from reptiles to mammals. Over evolutionary time, bones in the reptilian jaw joint have migrated into the middle ear of mammals and become co-opted for hearing. To examine the development of bone structure, the mouse fetus shown here was treated to make the tissue transparent, and dyed to label the cartilage and bone.