Birds are one of the most widespread and diverse classes of vertebrates, with over 10,000 recognized living species. Most birds are toothless, but some ancient birds and their modern relatives have true teeth. So how many types of birds actually have teeth?
Do All Birds Have Teeth?
The simple answer is no – most living birds do not have teeth. Over 99% of modern bird species lack any form of teeth as adults. Most birds instead have beaks made of keratin that they use for eating, preening, manipulating objects, courting, and defending themselves.
Early in their development, many baby birds have an egg tooth or caruncle on their beaks which they use to break out of their shells at hatching. But these egg teeth do not persist into adulthood. True teeth anchored in the jaw bone have been completely lost in most modern birds.
When Did Birds Lose Their Teeth?
While the vast majority of living bird species lack teeth, the earliest birds from the Jurassic and Cretaceous Periods still had teeth. The fossil record indicates that ancestral birds evolved from toothed, reptilian dinosaurs in the Jurassic Period over 150 million years ago. These early birds retained their ancestors’ teeth.
Birds then started gradually losing their teeth approximately 116-99 million years ago during the Cretaceous Period. By about 99 million years ago, toothless birds had become common. So birds maintained ancestral teeth for at least 50 million years before most species lost them as adults.
Why Did Birds Lose Their Teeth?
There are a few proposed explanations for why most birds lost their teeth and evolved beaks:
- Beaks are more lightweight, which helped enable flight.
- Beaks do not have tooth roots that require a bony socket in the jaw, so they can evolve faster and more flexibly in shape.
- Beaks and a toothless jaw may have been easier to maintain through the process of molting and regrowing feathers and bills.
- Beaks augmented with a muscular gizzard allow birds to efficiently process food through grinding and crushing.
The gains in precision, reduction of mass, and flexibility of beaks may have provided selective advantages that led to the loss of teeth through natural selection in most bird lineages.
Which Birds Still Have Teeth Today?
While the vast majority of birds today do not have teeth, there are a few living groups of birds that have retained their toothed ancestry:
Paleognaths
There are 10 living species of paleognaths or “ancient jaws” that have retained their ancestral teeth:
- Cassowaries – 3 species from Australasia
- Emus – 2 species from Australia
- Kiwis – 5 species from New Zealand
- Tinamous – 47 species from Central and South America
These birds are characterized by a distinctive palate structure in their upper jaw bone. They are thought to be the most ancient group of living birds, which helps explain why they have retained teeth when other lineages lost them.
Neotropical Seriemas
The two living species of seriemas from South America also have simple cone-shaped teeth lodged in grooves of their upper and lower beaks:
- Red-legged seriema
- Black-legged seriema
Seriemas are related to falcons and form another early-diverging lineage of living birds.
Ancient Bird Relatives
There are also some ancient bird relatives outside of the traditional bird classification that have teeth:
- Mesozoic Hesperornithids – Extinct toothed diving birds
- Ichthyornis – Extinct toothed seabird
These examples showcase that teeth have been retained in a few of the most ancient bird lineages, but lost in most modern bird groups over evolutionary time.
How Many Teeth Do Toothed Birds Have?
The number of teeth in birds with teeth depends on the species. Here are some examples:
Species | Number of Teeth |
---|---|
Cassowaries | 24 |
Emus | 34-50 |
Red-legged seriemas | 5-6 upper teeth, 7-9 lower teeth |
Birds with teeth tend to have a relatively small number compared to their reptilian ancestors. For example, the dental formula of a common cassowary is:
Upper jaw: 0 incisors, 5 premolars, 3 molars
Lower jaw: 0 incisors, 5 premolars, 4 molars
Their teeth are usually cone-shaped and lack other cusps and elaborate crowns seen in complex reptile teeth. The simpler cone teeth are enough for these birds to grasp and swallow their food, while their muscular gizzards further grind and digest it.
Do Pet Birds Have Teeth?
No, common pet birds such as parrots, cockatoos, budgies, and finches lack any true teeth as adults. Chicks may have a temporary egg tooth that drops off.
Many pet birds use their sharp beaks for cracking hard nuts and seeds. But they do not have anchoring teeth in their jaw bones. Some birds like cockatoos have evolved a built-in “pseudotooth” on their upper beak to help crack into nuts.
Most pet birds swallow food whole or use their muscular gizzard to grind food down. Pet birds carefully fed a balanced diet do not need functional teeth for healthy digestion.
Conclusion
Only a small fraction of birds still living today have true teeth. Most living birds lack any teeth as adults. Based on the fossil record, it appears ancestral birds evolved from toothed dinosaur ancestors but then lost their teeth approximately 99 million years ago in the Cretaceous Period.
The major groups of living toothed birds include paleognaths like cassowaries and emus, seriemas, and a few ancient lineages like hesperornithids. These birds retained simple cone-shaped teeth, while other bird groups evolved toothless beaks.
While teeth were essential for the first toothed bird species, most groups have adapted well without them for tens of millions of years. Beaks augmented by muscular gizzards have allowed most birds to bite, grind, and swallow food just fine without teeth.