The first hard evidence for the ‘outside-in’ theory of the origin of teeth

Date:

Share post:

Researchers studying a 400 million year old bony fish from Estonia believe that they have found evidence for the origins of teeth. Using advanced synchrotron microtomography on numerous specimens representing different ages has allowed scientists a rare glimpse into the evolution and formation of teeth.

The first hard evidence for the 'outside-in' theory of the origin of teeth
Synchrotron scans of Lophosteus jaws [Credit: Donglei Chen]

As lead author Donglei Chen explains, “We can watch how fishes initiated and replaced teeth one by one, and how the blood vessels of these teeth were formed, 400 million years ago. It is as if we have traveled through a space-time portal to a living, microscopic world inside the fossil bones.”

Teeth consist of a soft pulp surrounded by dentine and covered by a mineralized substance such as enamel. Some researchers believe that teeth evolved from dermal scales around the mouth region in primitive fishes called odontodes.

The first hard evidence for the 'outside-in' theory of the origin of teeth
Synchrotron scans of Lophosteus jaws [Credit: Donglei Chen]

But as Donglei Chen states, “To understand the origin of teeth, people have tended to search for dermal odontodes that look like teeth. However, even if the extra-oral ‘teeth’ have all the features thought to be unique to true teeth, this may only represent convergent evolution based on a flexible developmental tool kit shared by all dermal teeth.”

Based on their work of one of the earliest known bony fishes, Lophosteus superbus, from the Late Silurian of Estonia, Uppsala University researchers looked for clues into the origins of teeth. This fish had many skull ornamentations that were similar to earlier groups of fishes called arthrodires.

The first hard evidence for the 'outside-in' theory of the origin of teeth
Synchrotron scans of Lophosteus jaws [Credit: Donglei Chen]

Some of these ornamentations on and around the mouth had a dome-shaped appeared that the researchers referred to as ‘tooth cushions’. These tooth cushions appear to represent the most primitive form of a tooth battery within the mouth.

By using synchrotron microtomography, Chen and his colleagues were able to reconstruct 3D images of specimens of different ages in order to compare the growth history and development of the teeth. Chen adds, “By modelling the successive resorption surfaces in three dimensions it allows us to visualize the entire developmental trajectory of the dentition”. As a result, the dental development of Lophosteus may cast light on the possible origin of teeth from dermal odontodes, and on the evolutionary relationship between dentitions of all jawed animals.

This research will be presented at the 77th Annual Society of Vertebrate Paleontology meeting in Calgary, Canada.

Source: Society of Vertebrate Paleontology [August 24, 2017]

ADVERTISEMENT

spot_img

Related articles

Underwater ancient cypress forest offers clues to the past

When saber-toothed tigers, woolly mammoths and giant sloths roamed North America during the last Ice Age about 18,000...

Dinosaur footprints discovered on Scottish island

Dozens of giant footprints discovered on a Scottish island are helping shed light on an important period in...

Two tiny beetle fossils offer evolution and biogeography clues

It is well-known that living fossils exhibit stasis over geologically long time scales. Examples are the panda and...

Modern snakes evolved from a few survivors of dino-killing asteroid

A new study suggests that all living snakes evolved from a handful of species that survived the giant...

Researchers recover ancient mammoth tusk during deep-sea expedition off California coast

The ocean’s dark depths hold many secrets. During an expedition aboard the R/V Western Flyer in 2019, ROV...

‘Steak-knife’ teeth reveal ecology of oldest land predators

The first top predators to walk on land were not afraid to bite off more than they could...

New birdlike dinosaur had modern feathers

In its time, about 125 million years ago, it must not have seemed remarkable. Jianianhualong tengi was just...

Sediments from lake in Japan reveal stable climate led to origin of agriculture

The development of agriculture was a landmark feat for modern humans. It marked the beginning of a sedentary...