thumb|left|upright|Archaeopteryx lithographica (Berlin specimen) Several non-avian dinosaurs had feathers on their limbs that would not have functioned for flight. One theory suggests that feathers originally evolved on dinosaurs due to their insulation properties; then, small dinosaur species which grew longer feathers may have found them helpful in gliding, leading to the evolution of proto-birds like Archaeopteryx and Microraptor zhaoianus. Another theory posits that the original adaptive advantage of early feathers was their pigmentation or iridescence, contributing to sexual preference in mate selection. Dinosaurs that had feathers or protofeathers include Pedopenna daohugouensis and Dilong paradoxus, a tyrannosauroid which is 60 to 70 million years older than Tyrannosaurus rex.
thumb|left|upright|Archaeopteryx lithographica (Berlin specimen) Several non-avian dinosaurs had feathers on their limbs that would not have functioned for flight One theory suggests that feathers originally evolved on dinosaurs due to their insulation properties; then small dinosaur species which grew longer feathers may have found them helpful in gliding leading to the evolution of proto-birds like Archaeopteryx and Microraptor zhaoianus Another theory posits that the original adaptive advantage of early feathers was their pigmentation or iridescence contributing to sexual preference in mate selection Dinosaurs that had feathers or protofeathers include Pedopenna daohugouensis and Dilong paradoxus a tyrannosauroid which is 60 to 70 million years older than Tyrannosaurus rex