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Rotation of the earth around the sun paces daily biologic rhythms (circadian rhythms). Additional rhythms spanning days are mutidien. The energy for biologic rhythms is provided by metabolism. We measured biologic rhythms in dinosaur’s fossilized feather and rachis imprints and in contemporaneous wild turkey tail-feather. Daily growth lines were measured in 9 photographs of dinosaur feather-imprints. They were from an enantiornithine bird (Mesozoic 245-265 million years), from a troodontid theropod (Cretaceous ~160 million years) and from Sinosauropteryx (Early Cretaceous; ~125 million years; rachis only). We measured 27 growth lines and 39 rachis intervals in the turkey feather. We compared our measurements in the dinosaurs to those in the modern feather. We used biometrics to analyze the measurements, we found circadian and multidien rhythms in all feathers. The gliding Microraptor had large feathers. In contrast, the feathered dinosaurs had smaller feathers. Wild turkey feathers were of intermediate size.  We conclude, based on measurements and statistically identified spectral peaks, that circadian and multidien rhythms are present in feather imprints of dinosaurs and in extant birds similar to those described in mammals. Feather growth is related to metabolism, to function and to body mass; this suggests a similar metabolism in feathered dinosaurs and modern birds.

Biological Rhythms, Metabolism and Function in Feathered Dinosaurs; As Determined by Biostatistics