The common ancestors of birds and mammals were very early (stem)reptiles,which almost certainly possessed three-chambered hearts (two atria,one ventricle).Birds and mammals,however,are alike in having four-chambered hearts (two atria,two ventricles).The four-chambered hearts of birds and mammals are best described as

Question

Quizplus · Accepted Answer

The four-chambered hearts of birds and mammals are considered homoplasies, which means they are similar structures that evolved independently in the two lineages, not due to a direct common ancestor with a four-chambered heart. This is an example of convergent evolution, where similar environmental pressures lead to similar adaptations in different lineages.

The Common Ancestors of Birds and Mammals Were Very Early