In order for the four-chambered hearts of birds and mammals to be homologous, which other organisms would have to have had four-chambered hearts?
A) dinosaurs
B) thecodonts
C) plesiosaurs
D) synapsids
E) stem reptiles

Question

Quizplus · Accepted Answer

For the four-chambered hearts of birds and mammals to be homologous, their common ancestor, which is a stem reptile, would need to have had a four-chambered heart. Homologous structures are derived from a common ancestor.

In Order for the Four-Chambered Hearts of Birds and Mammals