Homologous structures are anatomical signs ofevolution that derived from a similar lineage. Mammals and their extinctrelatives contain an indentation in the skull behind each eye socket called thesynapsid opening.
Living mammals have inherited the same opening, except it’slarger. As larger openings evolved, jaw muscles and chewing motions came to be.There is a muscle for chewing that extends from the lower jaw to up to theopening evolved.
This might have led to better chewing and digestion. Also,three middle ear bones were an advanced feature. The two additional ear boneshelped form a joint between the upper and lower jaws. As time progressed, theear bones decreased in size and moved towards the lower jaws, forming a newjoint. “Other advanced features of mammals include having hair and producingmilk for their young. Unfortunately, features like these leave no trace in mostfossils. (AmericanMuseum of Natural History, n.
d.).” Analogous structures are opposite of HomologousStructures, they are convergent features of different species that havestructures that preform the same task, but are not alike in structure. Thesespecies did not evolve from a common ancestor, they just evolved in response toa similar environment.