Species basal to these groups are known to have feathers, so unless they were secondarily lost, they would have had quite the plumage. As you can see above, the Deinonychosauria (Dromaeosaurids and Troodontids) fit within the Aviremigia, all of which had penneceous feathers. These are advanced feathers with a central shaft, vanes and flattened barbs, with barbules connecting the barbs. Essentially, modern feathers (flight feathers are an asymmetrical modification of this design).
It is reasonable to assume that other theropods outside of Aviremigia had feathers also, but of more primitive structure. Looser with no barbules, for example, or radial and downy.
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