Readers ask about Microraptors, an X-ray map of the sky and more

Birds of a fossil feather

Four-winged Microraptor, perhaps one of the earliest flying dinosaurs, may have molted just a bit at a time — similar to modern songbirds, Carolyn Gramling reported in “This dinosaur may have shed its feathers like modern songbirds” (SN: 8/15/20, p.