are homologous to quill knobs present on some modern birds; the knobs
are related to the insertion area of follicular ligaments that anchor
the roots of the flight feathers (remiges) to the arm. We propose
that *Concavenator* has integumentary follicular structures inserted
on the ulna, as in modern birds. Because scales do not have
follicles, we consider the structures anchored to the *Concavenator*
arms to be non-scale skin appendages homologous to the feathers of
modern birds. If this is true, then the phylogenetic bracket for the
presence of non-scale skin structures homologous to feathers in
theropod dinosaurs would be extended to the Neotetanurae, enlarging
the scope for explaining the origin of feathers in theropods.