Crocodiles are known as terrifying predators, but some of their old relatives who roamed the planet 200 million years ago were vegetarian, research shows.
Fossils have been revealed between three and six members of the crocodile and alligator family with specialized teeth for chewing on plants.
Researchers reconstructed their vegetarian diets by analyzing the fossils of 146 teeth from 16 crocodyliforms.
Many of their & # 39; complex & # 39; teeth were formed unlike any modern herbivore until the herbivores were eradicated together with the dinosaurs 66 million years ago.
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Modern crocodiles had age-old, vegetarian cousins who roamed the planet 200 million years ago, research shows. Pictured: Crocodyliform life reconstructions of two extinct herbivorous varieties
HOW DO CROCODILES AND CABLES DIFFERENT?
Muzzle: Alligators have wider, U-shaped muzzles, while the crocodile is more pointed and V-shaped.
Smile: crocodiles look like they flicker a broad grin when their muzzles are closed.
Alligators teeth are hidden if their upper jaw is wider than their lower jaw.
At home: crocodiles live in saltwater habitats, while alligators look for freshwater marshes and lakes.
Study author Keegan Melstrom, a PhD student at the University of Utah, USA, said: & The most interesting thing we discovered was how often it seems extinct crocodyliforms ate plants.
& # 39; The carnivores have simple teeth, while herbivores have much more complex teeth.
& # 39; Omnivores, organisms that eat both plant and animal material, fall somewhere in between.
& # 39; Our study indicates that complex-shaped teeth, which we deduce to indicate herbivory, occur at least three times in the extinct family of crocodiles and perhaps even six.
& # 39; Part of my previous research has shown that this pattern applies to living reptiles with teeth, such as crocodiles and lizards.
& # 39; These results told us that the basic pattern between food and teeth is found in both mammals and reptiles, despite very different tooth shapes, and applies to extinct reptiles. & # 39;
Dental fossils revealed between three and six members of the crocodile and alligator family had specialized teeth for chewing on plants. Shown: 3D prints of extinct crocodyliform teeth (blue), a skull of an extinct crocodyliform and skulls of living representatives of this group
This image is a collection of 3D images with fake colors that represent the range in the form of crocodyliform teeth. Carnivores (left), such as the living Caiman, have simple teeth, while herbivores (right) have much more complex teeth
WHAT DO WE KNOW ABOUT THE EVOLUTION OF CROCODLES?
Of all the reptiles that live today, crocodiles are perhaps the least changed from their prehistoric ancestors from the late Cretaceous period, more than 65 million years ago
The even earlier crocodiles from the Triassic and Jurassic periods, however, had a number of clearly non-crocodile-like characteristics, such as bipedal postures and vegetarian diets.
Together with pterosaurs – the family of flying reptiles – and their relatives on land dinosaurs, crocodiles were a spur of the archosaurs, the & # 39; rulers of the ruling lizards & # 39; from the early to the middle of the Triassic era.
The earliest dinosaurs and the earliest crocodiles looked much more alike than the first pterosaurs, which also evolved from archosaurs.
What distinguished the first crocodiles from the first dinosaurs was the shape and muscular system of their jaws, which were usually much more deadly, as well as their relatively expanded limbs – as opposed to the straight, & # 39; locked up & # 39; legs of theropode dinosaurs.
It was only in the Mesozoic that crocodiles developed the three most important traits with which they are associated today: blunt legs; slim, armored bodies and marine lifestyles.
All crocodylians who live today have a similar body shape with relatively simple, conical teeth, ideal for their semi-aquatic generalistic carnivorous lifestyle.
But the dental fossils in the study were clearly non-carnivorous and seemed to have specialized forms that cannot be seen in modern animals.
Mr. Melstrom and Dr. Randall Irmis, chief paleontology curator at the Natural History Museum of Utah, USA, compared the tooth complexity of extinct crocodyliforms with that of living animals to work out what they ate.
They used a method originally developed for use in live mammals – measuring the size and morphological characteristics of the teeth at a resolution of 25 rows of data per tooth.
Researchers reconstructed their vegetarian diets by analyzing the fossils of 146 teeth from 16 crocodyliforms. Pictured: a living descendant of crocodiles, the South American crocodile of the Caiman – a carnivore
Many of their & # 39; complex & # 39; teeth were formed unlike any modern herbivore until the herbivores were eradicated together with the dinosaurs 66 million years ago. Pictured: Reconstructions of extinct carnivorous and mixed meat and herbivorous varieties
WHAT IS THE TIME OF CROCODILE EVOLUTION?
250,000,000 BC -Xilousuchus
Three feet long. 5-10lbs. Lived in the swamps of East Asia. Ate small animals. Ridge of fan-like & # 39; sailing & # 39; on their backs. Split into prehistoric crocodiles and early dinosaurs.
228,000,000 BC. – Phytosaur
Alive during the early Jurassic period. Most related to crocodile species. Herbivores. Looks a lot like modern crocodiles – except that their nostrils were on the top of their heads instead of the top of their snouts.
200,000,000 BC. – Erpetosuchus
Biped. Did not look like modern crocodiles in terms of behavior or body shape, except the shape of their head.
110,000,000 BC. – Sarcosuchus
Middle Cretaceous period. 40ft long. 10-15 tons. Ate dinosaurs and fish. Lived in the rivers of Africa. Strange protrusion on its muzzle. Looked and behaved as if they were modern decedents, but it was twice as long and about ten times as heavy.
100,000 BC. – Stomatosuchus
36 ft long. ten tons. Ate plankton and krill with its high pelican-like jaw.
80,000,000 BC. – Beinosuchus
Greek for terrible crocodile. Lived in the rivers of North America. About 33 ft long and 10 tons. They had a 6ft. long skull. Fed by fish, crustaceans and land animals. Evidence in fossils suggests that they have attacked large North American tyrannosaurs.
70,000,000 BC. – Champsosaurus
Five feet tall, 25-50 pounds, ate fish and lived in the rivers of North America and Western Europe. Long narrow profile and a snout strewn with teeth. Survived the extinction of the Cretaceous-Paleogene extinction event that killed three-quarters of the plant and animal species on earth – including the dinosaurs.
65,000,000 BC. – Chalk paleo extinction event
Non-avian dinosaurs were swept away and more than half the species in the world were destroyed. This massive extinction paved the way for the emergence of mammals and the appearance of humans.
55,000,000 BC. – Crocodylidae (modern crocodile)
The modern crocodile – including the saltwater, Nile and American variants – spread throughout the world. Although it looks prehistoric, it is a highly developed and complex organism that is a successful predator.
23,000.00 BC. – Quinkana
Nine feet long, 500 pounds. Consumed red meat in forests. Long curved teeth and long legs, in contrast to the short legs of modern croc. These crocodiles are constantly becoming smaller due to changes in the environment.
4,200,000 BC. – Crocodylus thorbjarnarsoni
This is a very close relative of today's crocodile. Large skull and small raised edge for the eyes. Probably prayed for early people. Lived in the Turkana basin in Kenya. Perhaps the biggest known real crocodile.
Mr Melstrom said the unexpected variety in teeth of crocodyliforms showed they could thrive in a larger range of ecological environments than previously thought.
He also discovered that the herbivores appeared in the evolutionary history of the family shortly after the end of the Triassic extinction some 200 million years ago.
They existed until the Cretaceous mass extinction that butchered all dinosaurs except birds.
The fossil analysis suggested that between three and six species of herbivorous feed developed during the Mesozoic.
Mr. Melstrom said: & # 39; Our work shows that extinct crocodyliforms had an incredibly varied diet.
& # 39; Some were similar to live crocodiles and were predominantly carnivorous, others were omnivores and others probably specialized in plants.
& # 39; The herbivores lived on different continents at different times, some alongside mammals and mammalian relatives, and others not.
& # 39; This suggests that a herbivorous crocodyliform was successful in various environments. & # 39;
He planned to continue to reconstruct the diet of extinct crocodyliforms, including fossil species that lack teeth.
The researcher also wanted to understand why the extinct relatives of crocodiles were so radically diversified after one massive extinction, but not the one who killed the dinosaurs – and whether food ecology had played a role.
The study by the University of Utah and the National History Museum of Utah in the US was published in the journal Current biology.
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