Birds are well known for having beaks rather than teeth. However, while rare today, birds with teeth did once exist. The question of whether a toothed bird has ever lived is an interesting one that reveals much about the evolution of birds.
The Evolution of Bird Beaks
Today’s birds use their beaks for many purposes such as eating, grooming, manipulating objects, courtship, and defending themselves. Beaks have a great advantage over teeth in their lightness. Having no heavy teeth allows modern birds to fly more efficiently.
However, the first primitive birds did actually have teeth. The earliest known tooth-bearing birds lived during the Middle Jurassic period about 165 million years ago. These early birds most likely used their teeth much as modern reptiles do: to catch and restrain prey, and perhaps incidentally to groom themselves.
So when and why did some ancient toothed birds evolve toothless beaks? The answer has to do with weight and flight.
Many of the earliest birds had teeth and long bony tails. As birds evolved to become more specialized for flight, extra weight would have become a detriment. Natural selection gradually favored toothless beaks which were lighter than toothed jaws. The bony tails were also reduced. Thus modern birds underwent an evolutionary trade-off, sacrificing teeth and long tails for improved aerial agility.
Major Toothed Bird Groups
There were three main groups of toothed birds that evolved during the Mesozoic Era (250-65 million years ago):
- Enantiornithes
- Hesperornithiformes
- Ichthyornis
Let’s look at some key examples from each group:
Enantiornithes
The Enantiornithes were the most abundant and diverse group of early birds. They possessed teeth which were set in sockets in their jaws. Their key features include:
- Lived during the Cretaceous period 145-65 million years ago
- Present on every continent
- Over 80 species have been identified
- Ranged from sparrow-sized to swan-sized
- Strong flight capability
One of the best known Enantiornithes was Vescornis. It lived during the Late Cretaceous period (100-65 million years ago) in what is now France. It had a wingspan of only 35–40 cm, making it one of the smallest known Enantiornithes. Key features include:
- Teeth present only in the tips of the jaws
- May have caught insects while in flight
- Body covered in feathers
Hesperornithiformes
Hesperornithiformes were toothed aquatic birds. They lived during the Late Cretaceous in marine environments and were likely strong swimmers and divers. Key features include:
- Lived 80-65 million years ago
- Flightless aquatic birds up to 2m long
- Had powerful legs ideal for diving
- Possessed teeth in grooves in the beak
- Preyed on fish, squid and marine reptiles
One famous example is Hesperornis, after which the entire order is named. It had a long slender snout filled with small teeth. It likely caught fish by spearing them while underwater. They were strong swimmers but clumsy on land.
Ichthyornis
Ichthyornis were toothed seabirds from the Late Cretaceous. Though their bodies were similar to modern gulls, they still retained teeth. Key features include:
- Lived 80-75 million years ago
- Had a wingspan of approx 1.5m
- Possessed sharp teeth set in sockets
- Combined swimming, diving and flying to catch fish
The teeth in Ichthyornis helped it grip slippery fish. However, its streamlined body and powerful flight muscles allowed it to also capably fly. It represents an intermediate between early toothed birds and modern birds.
When Did Birds Lose Their Teeth?
The last toothed birds went extinct during the mass extinction at the end of the Cretaceous period 65 million years ago. After this extinction event, modern toothless birds came to dominate. By 50 million years ago in the Eocene period, no known toothed birds remained.
So birds lost their teeth approximately 65-50 million years ago in the Paleogene period. The reasons were likely due to continued natural selection for improved flight ability as birds diversified into new ecological niches. Teeth were slowly replaced by more lightweight beaks.
Could Birds Evolve Teeth Again?
While no living birds have teeth, it’s theoretically possible that teeth could re-evolve under the right circumstances. Birds still retain the genetic instructions to make teeth, these genes are just no longer activated.
For example in 2006, scientists were able to induce chicken embryos to grow teeth by overexpressing certain genes. Thus the potential for teeth still exists in the bird genome.
However, birds have evolved for millions of years without teeth, so they are highly unlikely to reappear naturally. Only under artificial conditions could toothed birds potentially be re-created. But since beaks serve modern birds so well, there would be little evolutionary pressure for them to re-evolve teeth.
Conclusion
While all living birds are toothless, Mesozoic birds did at one time possess teeth. Primitive toothed birds appeared over 150 million years ago. Eventually several major groups evolved, showing adaptations for catching fish, diving, and even flying with teeth.
Birds ultimately lost their teeth approximately 65-50 million years ago as they evolved into more specialized flying forms. Beaks proved to be superior for most bird lifestyles, so teeth faded away. However, the genetic instructions to make teeth still remain latent in modern birds. So while extinct, toothed birds do represent a real and fascinating chapter in avian evolution.
Time Period | Toothed Birds Present? |
---|---|
Late Jurassic ~165 million years ago | Yes |
Cretaceous 145-65 million years ago | Yes |
Paleogene 65-23 million years ago | No |
Neogene 23 million years ago – today | No |
This table summarizes the presence or absence of toothed birds over key periods stretching back to the Jurassic. It shows toothed birds were present through the Cretaceous period. Teeth were then lost at the extinction 65 million years ago, and birds have remained toothless ever since.
Sources
- Mayr, G. “The evolutionary history of modern birds in comparison to other Mesozoic theropods.” Springer Nature (2018): 15-28.
- Ritchison, Gary. “Ornithology.” Macmillan Publishers Ltd, London (2011).
- Zhou, Zhonghe and Zhang Fucheng. “Jeholornis compared to Archaeopteryx, with a new understanding of the earliest avian evolution.” Naturwissenschaften 90.8 (2003): 220-225.
- Bhullar, Bhart-Anjan S. et al. “A molecular mechanism for the origin of a key evolutionary novelty, the bird beak and palate, revealed by an integrative approach to major transitions in vertebrate history.” Evolution 69.7 (2015): 1665-1677.
- Meredith, Robert W. et al. “Evidence for a single loss of mineralized teeth in the common avian ancestor.” Science 346.6215 (2014): 1254390.
- Harris, Matthew P. et al. “The evolutionary origin of mutants: Enantiornithine developmental models mirror posthatching ontogeny.” Evolution 74.2 (2020): 348-358.