Image courtesy of the Maungatautari Ecological Island Trust, public domain
Joel Kontinen
Joel Kontinen
An organ that
allows some birds to detect the movement of hidden prey by plunging their beaks
into the ground seems to have been present in early birds 70 million years
ago, and probably first appeared in their dinosaur ancestors.
It probably arose
during the fall of man, when animals were also affected and diseased.
Special “remote
touch” sensory receptors known as Herbst corpuscles, which are found within
densely packed pits in the beak’s tip, help birds detect the movement of worms
in soil or small fish in water – even several centimetres away from the beak.
This effectively gives birds a “sixth sense”, according to Carla du Toit
at the University of Cape Town in South Africa and her colleagues.
To work out when
the sixth sense evolved, du Toit and her colleagues studied the beaks of
hundreds of modern and ancient birds, including four species of lithornithids, an
extinct group of birds that lived alongside dinosaurs during the Cretaceous
period.
Lithornithids
belong to one of the two major types of birds alive today, the palaeognaths,
which include kiwis, ostriches and emus. The other
major group is the neognaths.
By examining
specimens of modern birds, the researchers identified distinct pitting patterns
in the beak associated with Herbst corpuscles, says du Toit. The team then
found those same patterns in lithornithid fossil beaks, which suggests that
lithornithids had the same sensory abilities and were probe-foraging birds.
The discovery makes sense because Herbst corpuscles
are found in both palaeognaths and neognaths. The two groups separated from one
another more than “70 million years” ago, which would suggest that Herbst
corpuscles evolved in the common ancestor of both bird groups.
That millions of years is based on not taking the Noah’s
Flood into consideration.
In fact, the
sensory structures might have evolved in dinosaurs, says du Toit. A “sixth
sense” feature might have helped carnivorous theropods such as Neovenator find prey by probing their snouts into mud or
murky water, she says.
The researchers
hope in future to find if the pitting was present in the beaks of an ancient
group of winged reptiles, the pterosaurs. However, the poor quality of most fossils
make such an analysis difficult, says du Toit.
Source:
Lesté-Lasserre, Christa. 2020. Bird beak extra sense evolved more than 70 million years ago. New Scientist 2 December
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