Data from: Cretaceous origins of the vibrotactile bill-tip organ in birds

Some probe-foraging birds locate their buried prey by detecting mechanical
vibrations in the substrate using a specialised tactile bill-tip organ
comprising mechanoreceptors embedded in densely clustered pits in the bone
at the tip of their beak. This remarkable sensory modality is known as
“remote-touch”, and the associated bill-tip organ is found in
probe-foraging taxa belonging to both the paleognathous (in kiwi) and
neognathous (in ibises and shorebirds) clades of modern birds.
Intriguingly, a structurally similar bill-tip organ is also present in the
beaks of extant, non-probing paleognathous birds (e.g. emu and ostriches)
that do not use remote-touch. By comparison with our comprehensive sample
representing all orders of extant modern birds (Neornithes), we provide
evidence that the lithornithids (the most basal known paleognathous birds
which evolved in the Cretaceous period) had the ability to use
remote-touch. This finding suggests that the occurrence of the “vestigial”
bony bill-tip organ in all modern non-probing paleognathous birds
represents a plesiomorphic condition. Furthermore, our results show that
remote-touch probe-foraging evolved very early among the Neornithes and it
may even have predated the paleognathous-neognathous divergence. We
postulate that the tactile bony bill-tip organ in Neornithes may have
originated from other snout tactile specializations of their non-avian
theropod ancestors.