A HYPOTHESIS ON THE EVOLUTIONARY ORIGIN OF THE SQUAMOSAL BONE IN THE THERIAN MAMMALS

In the structure of the sidewall of braincase of mammals, the advanced therians (Metatheria and Eutheria) are characterized by their peculiar property of the squamosal, which is located in the front of the petrosal and takes part in the construction of the side wall of the braincase, but all the rest of the mammals have a squamosal, which is located in the back of the petrosal without taking part in the construction of the sidewall of the braincase.