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A small dinosaur that scampered across north-western China 160m years ago boasted a trait not seen in any other dinosaur or other prehistoric creature: it was born with teeth but became toothless by adulthood.

Scientists said fossils of 19 individuals of a dinosaur called Limusaurus, ranging in age from under a year to 10 years, showed that juveniles had small, sharp teeth but adults developed a toothless beak.

Only rarely have scientists found fossils of a dinosaur species ranging from babies to adults, a sequence revealing anatomical changes that unfold as an animal matures.



Limusaurus was a lightly built two-legged dinosaur with short arms and long, slender legs. It may have had down-like feathers covering at least part of its body. The largest ones were just under two metres long. This cluster of dinosaurs, found in Xinjiang province, apparently became trapped in a mud pit and died.

Dinosaur tail trapped in amber offers insights into feather evolution Read more

“It probably looked something like an emu with a long tail,” said Joey Stiegler, a paleontologist at George Washington University and one of the researchers behind the study published in the journal Current Biology.

Such tooth loss is called ontogenetic edentulism. Some animals alive today have it, including the egg-laying Australian mammal the platypus.

The adult Limusaurus were found with stones called gastroliths that some plant-eating dinosaurs swallowed to grind up plant material in the stomach. The babies lacked these.

The tooth loss and gastroliths indicate Limusaurus underwent a dramatic dietary change from birth to adulthood, starting life perhaps eating insects and small vertebrates before later turning to plants.

Limusaurus is a member of the theropod dinosaur group within which birds evolved.

James Clark, a paleontologist at George Washington University, said the findings suggested species close to the origin of birds might have gone through a similar development, and tooth loss might have been gradual during the evolutionary origin of birds.

“This is important in showing that growth and development in dinosaurs was more complex than previously suspected, and it provides a model for a stage that birds may have gone through in evolving their beak,” Clark added.

Birds, first appearing about 150m years ago, evolved from small feathered dinosaurs. The earliest ones had teeth. Over tens of millions of years, many evolved toothless beaks like those in today’s birds. The last birds with teeth died with the dinosaurs, about 66m years ago.</s>A modest little dinosaur that scampered across northwestern China 160 million years ago boasted a unique trait not seen in any other dinosaur or other prehistoric creature yet unearthed: it was born with teeth but became toothless by adulthood.

Scientists on Thursday said fossils of 19 individuals of a dinosaur called Limusaurus, ranging in age from under a year to 10 years, showed that juveniles had small, sharp teeth but adults developed a toothless beak.

This cluster of dinosaurs, found in Xinjiang Province, apparently became hopelessly trapped in a mud pit and died.

Only rarely have scientists found fossils of a dinosaur species ranging from babies to adults, a sequence revealing various anatomical changes that unfold as an animal matures.

Limusaurus was a lightly built two-legged dinosaur with short arms and long, slender legs. It may have had down-like feathers covering at least part of its body. The largest ones were about 6 feet long (under 2m).</s>Bite the dust: meek dinosaur lost its teeth as it hit adulthood

WASHINGTON, Dec 22 (Reuters) - A modest little dinosaur that scampered across northwestern China 160 million years ago boasted a unique trait not seen in any other dinosaur or other prehistoric creature yet unearthed: it was born with teeth but became toothless by adulthood.

Scientists on Thursday said fossils of 19 individuals of a dinosaur called Limusaurus, ranging in age from under a year to 10 years, showed that juveniles had small, sharp teeth but adults developed a toothless beak.

This cluster of dinosaurs, found in Xinjiang Province, apparently became hopelessly trapped in a mud pit and died.

Only rarely have scientists found fossils of a dinosaur species ranging from babies to adults, a sequence revealing various anatomical changes that unfold as an animal matures.

Limusaurus was a lightly built two-legged dinosaur with short arms and long, slender legs. It may have had down-like feathers covering at least part of its body. The largest ones were about 6 feet long (under 2 meters).

"It probably looked something like an emu with a long tail," said George Washington University paleontologist Joey Stiegler, one of the researchers in the study published in the journal Current Biology.

Such tooth loss is called ontogenetic edentulism. Some animals alive today have it, including the egg-laying Australian mammal the platypus.

The adult Limusaurus individuals also were found with stones called gastroliths that some plant-eating dinosaurs swallowed to grind up plant material in the stomach. The babies lacked these.

The tooth loss and gastroliths indicate Limusaurus underwent a dramatic dietary change from birth to adulthood, starting life perhaps eating insects and small vertebrates before later turning to plants.

Limusaurus is a member of the theropod dinosaur group within which birds evolved.

George Washington University paleontologist James Clark said the findings suggest "species close to the origin of birds may have gone through a similar development, and tooth loss may have been gradual during the evolutionary origin of birds."

"This is important in showing that growth and development in dinosaurs was more complex than previously suspected, and it provides a model for a stage that birds may have gone through in evolving their beak," Clark added.

Birds, first appearing about 150 million years ago, evolved from small feathered dinosaurs. The earliest ones had teeth. Over tens of millions of years, many evolved toothless beaks like those in today's birds. The last birds with teeth died with the dinosaurs about 66 million years ago. (Reporting by Will Dunham; Editing by Sandra Maler)</s>Scientists have discovered a species of dinosaur that changed from a sharp-toothed carnivorous baby to a herbivorous adult with few very teeth.

The scientists found that in a group of 13 fossilised skeletons of the dinosaur Limusaurus inextricabilis, the younger animals had a head full of sharp teeth but, the older the animals, got the fewer they had left. The oldest and least toothy individual was 10 years old, according to the study published in the journal Current Biology.

Limusaurus inextricabilis was first discovered caught in a death trap of inescapable mud in Xinjiang Province, China. That's how it got its name: 'Limasaurus' means mired lizard, and 'inextricabilis' is fairly self-explanatory.

This species could grow to about 2 metres in length from tip to tail, and showed several developmental changes as it aged that support the theory that it became vegetarian in later life.

"The adult has a beak, very weak hands with no big claws, and it had rocks in its stomach like you see in birds that eat grains and plants," study co-author James Clark, a biologist at the George Washington University's Columbian College of Arts and Sciences in the US, told IBTimes UK.

It was hard to tell initially whether the dinosaurs were indeed undergoing a dramatic developmental change as they aged, or whether the small and large skeletons were actually from different species, says study co-author Shuo Wang of Capital Normal University in Beijing, China, in a statement.

"Initially, we believed that we found two different ceratosaurian dinosaurs from the Wucaiwan Area, one toothed and the other toothless, and we even started to describe them separately," Wang says.

Closer analysis confirmed that the dinosaurs were indeed of the same species, but just lost their teeth in later life.

The scientists analysed the fossil bones of the dinosaurs to see what it had been eating. They used stable-isotope analysis, which can show tell-tale traces of the animals' diets, as carnivores and herbivores tend to have different ratios of certain isotopes in their bones.

They compared the young and old dinosaurs with a carnivorous species of dinosaur found at the site – a member of the Tyrannosaur family – and a herbivorous dinosaur at the site – a sauropod. The younger Limusaurus inextricabilis had bone composition more like the tyrannosaur, while the older ones were more similar to the sauropod.

Such a transformation is rare among animals, although some still alive today, such as the platypus, also lose their teeth as they mature.

"A change in diet is not that unusual. Babies often are not able to eat the same things adults eat, and change their diet as they grow up," says Clark. "But it's very unusual to change the feeding apparatus going from baby to adult. You see that in some ways in tadpoles turning into frogs, as they have very different feeding apparatus.

"But in reptiles you just never almost see this."</s>Birds' beaks may have an evolutionary history that started with an adolescent dinosaur losing its teeth, scientists believe.

Limusaurus, which lived 160 million years ago, hatched from its egg equipped with rows of small, sharp teeth.

But as the creature matured into an adult all its teeth fell out, leaving only a beak-like set of jaws, a study has found.

Limusaurus belonged to the theropod family of two-legged dinosaurs that included the evolutionary ancestors of modern birds. Fossils found in the Xinjiang province show that the species was scampering around China around 160 million years ago. It had short arms and long, slender legs and may have had down-like feathers covering at least part of its body. The largest ones were about 6 feet long (under 2 metres).

Experts made the discovery after studying the fossilised skeletons of 19 dinosaurs that had died mired in mud in Xinjiang province, China.

The animals ranged in age from baby to adult, showing the pattern of tooth loss over time.

The find suggests Limusaurus began life as a carnivore or omnivore before turning vegetarian.

Its 'baby teeth' would have been needed for chewing meat.

Professor James Clark from George Washington University said: 'This discovery is important for two reasons.

'First, it's very rare to find a growth series from baby to adult dinosaurs.

'Second, this unusually dramatic change in anatomy suggests there was a big shift in Limusaurus's diet from adolescence to adulthood.'

Limusaurus belonged to the theropod family of two-legged dinosaurs that included the evolutionary ancestors of modern birds.

It had short arms and long, slender legs and may have had down-like feathers covering at least part of its body.

The largest ones were about 6 feet long (under 2 metres).

'It probably looked something like an emu with a long tail,' said George Washington University paleontologist Joey Stiegler, one of the researchers in the study published in the journal Current Biology.

The unusual loss of its teeth with age may help explain how the beak came into being, the study suggests.

Some animals alive today have it, including the egg-laying Australian mammal the platypus.

The adult Limusaurus individuals also were found with stones called gastroliths that some plant-eating dinosaurs swallowed to grind up plant material in the stomach.

The tooth loss and gastroliths indicate Limusaurus underwent a dramatic dietary change from birth to adulthood, starting life perhaps eating insects and small vertebrates before later turning to plants.

Another clue pointing to a link with birds was seen in the dinosaur's hands.

Its first finger was reduced in size, marking a likely transition towards the loss of the first and fifth fingers seen in later theropods.

Similarly, bird hands consist of the equivalent of a human's second, third and fourth fingers, and lack a first and fifth finger.

Birds, first appearing about 150 million years ago, evolved from small feathered dinosaurs, with the earliest ones having teeth.

Over tens of millions of years, many evolved toothless beaks like those in today's birds.

The last birds with teeth died with the dinosaurs about 66 million years ago.</s>The incredible discovery which is sure to be one of the most important paleontological finds ever, is a world first and now scientists have a once in a lifetime opportunity to study a piece of dinosaur which has travelled millions of years through time intact.

It is believed the tail belonged to a flightless dinosaur that lived approximately 99 million years ago in the mid-Cretaceous period.

The specimen was found in north eastern Myanmar, in an amber mine. It is believed the tail belongs to a juvenile coelurosaur, which is a type of therapod.

“This is the first time we’ve found dinosaur material preserved in amber,” said study co-author Ryan McKellar of the Royal Saskatchewan Museum in Canada. “We can be sure of the source because the vertebrae are not fused into a rod or pygostyle as in modern birds and their closest relatives.”

8 vertebrae are perfectly preserved in the amber, with many small delicate feathers, coloured brown on top and white underneath.

“It’s amazing to see all the details of a dinosaur tail – the bones, flesh, skin, and feathers – and to imagine how this little fellow got his tail caught in the resin, and then presumably died because he could not wrestle free,” said study co-author Prof Mike Benton from the University of Bristol.</s>Scientists in China have identified the first known dinosaur species that grew teeth as juveniles then lost them as adults, a finding that may explain why birds have beaks, a study said Thursday.

The research is based on fossils of a small and slender dinosaur known as Limusaurus inextricabilis, part of the theropod group of dinosaurs which were the ancestors of modern birds.

It likely ate meat as a youngster but transformed into a beaked adult that probably subsisted on plants, said the study in Current Biology.

“We found a very rare, very interesting phenomenon,” said lead author Shuo Wang of Capital Normal University in Beijing. “Toothed jaws in juvenile individuals transition to a completely toothless beaked jaw in more mature individuals during development.”

The results are based on an analysis of the fossilized remains of 13 ceratosaurian theropod dinosaurs, collected from the Upper Jurassic Shishugou Formation of northwestern China.

These remains allowed researchers to reconstruct the dinosaur’s growth from a hatchling to age 10.

The first scientific paper on Limusaurus was published in 2001, when researchers had just one fossilized juvenile. More specimens were unearthed in the following years.

“Initially, we believed that we found two different ceratosaurian dinosaurs from the Wucaiwan Area, one toothed and the other toothless, and we even started to describe them separately,” Wang said.

But then researchers realized the fossils looked quite similar, except for the teeth. Eventually they concluded that the specimens were the same species, some were just younger and had teeth.

“This discovery is important for two reasons,” said co-author James Clark, a professor of biology at George Washington University.

“First, it’s very rare to find a growth series from baby to adult dinosaurs. Second, this unusually dramatic change in anatomy suggests there was a big shift in Limusaurus’ diet from adolescence to adulthood.”

The theory of a change in diet is supported by the chemical makeup of the fossilized bones, the study said.

This process could help explain “how theropods such as birds lost their teeth, initially through changes during their development from babies to adults,” it added.

Among contemporary fish and amphibians, such tooth loss is commonly seen. The platypus, a beaked mammal, loses its teeth, too.

Researchers said the discovery of tooth loss in the Limusaurus marks the first in the fossil record and the first among reptiles.</s>As Limusaurus grew from adolescent to adult, it lost its teeth and did not grow a new set. Credit: George Washington University By comparing the fossilized remains of 13 ceratosaurian theropod dinosaurs known as Limusaurus inextricabilis collected from the Upper Jurassic Shishugou Formation of northwestern China, researchers have been able to reconstruct the dinosaur's growth and development from a young hatchling of less than a year to the age of 10. The findings, reported in Current Biology on December 22, uncovered something unexpected: the dinosaurs had teeth as young juveniles that were gradually lost as they grew up.

"We found a very rare, very interesting phenomenon in a ceratosaurian dinosaur whereby toothed jaws in juvenile individuals transition to a completely toothless beaked jaw in more mature individuals during development," says Shuo Wang of Capital Normal University in Beijing, China.

The findings make Limusaurus the first known reptile with the characteristic known as ontogenetic edentulism (meaning tooth reduction or loss in development). Together with other evidence, they led the researchers to conclude that the toothed juveniles were probably omnivorous meat-eaters. The beaked adults most likely transitioned to a plant-based diet.

Wang and colleagues first reported on this ceratosaurian back in 2001. At that point, they had collected just one fossilized juvenile, and they didn't yet know what it was. Over the course of the next several years, more specimens were found. But it wasn't clear that they all belonged to the same species.

"Initially, we believed that we found two different ceratosaurian dinosaurs from the Wucaiwan Area, one toothed and the other toothless, and we even started to describe them separately," Wang says.

As they started to code the dinosaurs' characteristics for phylogenetic analysis, they began to realize that they looked remarkably similar—all except for the teeth. With more careful study, the researchers concluded that in fact the specimens did represent the same dinosaur. It's just that those dinosaurs lost their teeth over time.

The researchers identified 78 developmental changes in Limusaurus in all, with tooth loss being the most surprising. They say that the discovery has significant implications for understanding the evolution of the beak, an important feeding structure in many dinosaurs of the past, as well as modern birds.

Wang says that tooth loss isn't so unusual in animals alive today. There are fish and an amphibian that lose teeth as they grow. Platypuses lose their teeth too. But the discovery is still a first for the fossil record and for reptiles.

The findings suggest that the dietary habits and needs of some dinosaurs changed over the course of their development, most likely along with shifts in their digestive systems. Wang and colleagues will continue studying changes to the digestive system and skeleton in greater detail.

Explore further: Dinosaurs' rise was 'more gradual,' new fossil evidence suggests

More information: Current Biology, Wang et al.: "Extreme Ontogenetic Changes in a Ceratosaurian Theropod" http://www.cell.com/current-biology/fulltext/S0960-9822(16)31269-6 , DOI: 10.1016/j.cub.2016.10.043</s>(Casper, Wyo.) - Bring the kids and enjoy mini summer vacation celebrating the Good Dinosaur! The Ramkota Hotel & Conference Center in Casper is now offering a Good Dinosaur, Great Hotel family package, valid through the end of September.
• 4 passes to Casper museums, including Tate Geological Museum (home of Dee the Mammoth and the Pleistocene Exhibit)

To book a room for the Good Dinosaur, Great Hotel package, click here</s>After a comparison of the fossilized remains of 13 ceratosaurian theropod dinosaurs found in China, it was found that their maturation from being babies to the age of 10 was a source of valuable information.

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The finding was reported in the journal Current Biology.

The really surprising fact was that they had teeth in their juvenile days but lost them as they grew up. This makes this dinosaur a rarity since it shows ontogenetic edentulism.

The toothed juveniles most probably ate all things including flesh. However, the beaked adults turned to more vegetarian stuff as a source of sustenance. The research began in 2001.

At that point in time only one sample had been collected and the scientists did not know what it was or what function it fulfilled in the scheme of things. As time progressed, more samples were found.

However, what remained a mystery was whether they all belonged to one species or to different species. At first it was thought that two distinct species had been chanced upon.

The toothed and the toothless varieties baffled scientists who thought that they were up against two different variants. However, as they looked deeper into the stuff the dinosaurs were made up of, they noticed that for all purposes they were the same with very little difference.

The only exception was the teeth. Finally the conclusion was reached that they were the same dinosaurs but with the difference that the juveniles had teeth while the mature species didn’t have any teeth but beaks instead. A total of 78 transformations were noted down. Yet tooth loss was the most prominent of them all.

This research points the way to the evolution of the beak which figures prominently in many species including some dinosaurs. Tooth loss is a process that takes place even today.

Even certain fish and an amphibian lose their teeth with time. Platypuses also let go of their teeth with the passage of time. Yet this discovery holds extra special meaning for the evolution of dinosaurs.

Apparently the diet strategies of various dinosaurs changed over time. Even their digestive systems underwent transformations in their structural-functional features. This special case of toothless dinosaurs is being looked into with great interest by scientists.
It is discovered that the Limusaurus dinosaur shed its teeth as it matured.