At least this clade of theropods had well-developed genuine feathers before the first known bird. Feathering in other groups of theropods is still uncertain. One compsognathid, "Sinosauropteryx", has plumaceous feathers, as does "Shuvuuia", another small theropod. Apparently, many small theropods carried feathers, whose function was thermoregulation (to keep warm).