Question

What occurred during the transition of the synapsid middle ear to the mammalian middle ear, and what are the evolutionary explainations?

Answer 1

The bones of the mammalian middle ear are like those of no other animals. Mammals have three bones where as reptiles and amphibians have only one and fish has no bone at all.

Over the course of evolution of mammals one bone from the lower and one from the upper jaw the articulate and quadrate bones lost their purpose in the jaw joint and were put to new use in the middle ear, connecting to the existing stapes bone, and forming the chain of three bones the ossicles which transmit sounds