Wednesday 10 February 2016


Dinosaurs replaced teeth like sharks

Giant plant-eating dinosaurs had rows of teeth stacked up behind each other like a shark and they replaced them once a month, scientists have found.

Dinosaurs replaced teeth like sharks
Image 1 of 2
Tooth replacement in the sauropod dinosaurs Camarasaurus and Diplodocus. Reconstructed skulls (A, D) and premaxillary teeth (B, C) of Camarasaurus (A, B) and Diplodocus (C, D). B and C include CT-generated sagittal and transverse sections of premaxillary alveoli and photographs of thin sections of Camarasaurus and Diplodocus Photo:
Dinosaurs replaced teeth like sharks
Image 1 of 2
Palaeontologists found that the herbivorous dinosaurs like Diplodocus had up to five replacement teeth lined up in each tooth socket Photo: PA

Palaeontologists found that the herbivorous dinosaurs like Diplodocus, which were some of the largest land animals to have ever lived, had up to five replacement teeth lined up in each tooth socket.

As the teeth wore down through chewing, they were shed and replaced by the next tooth in line.

Unlike large predatory dinosaurs like Tyrannosaurus rex, which replaced their teeth around once every two to three years, the large herbivorous sauropods replaced their teeth up to once a month.


Modern sharks also have rows of teeth that grow one behind the other to allow them to be continually replaced. Great White sharks replace their teeth around once every 230 days.

The speed of tooth growth and replacement in the giant plant-eating dinosaurs, however, has surprised scientists and has provided new insight into the volumes of food the animals consumed.

Growing up to 100 feet long, they would have needed to eat almost continuously to ensure they got enough energy from the nutritionally poor leaves and plants they consumed.

Dr Micheal D'Emic, from Stony Brook University in New York, said that this would have created huge amounts of wear on the teeth and they would have quickly worn away.

The findings also suggest that species such as the Diplodocus browsed plants close to the ground and so may have ended up with grit in their mouths that would also have caused wear.

Dr D'Emic said: "A nearly 100 foot long sauropod would have had a fresh tooth in each position about every one to two months, sometimes less.

"Effectively, sauropods took a 'quantity over quality' approach to making teeth, opposite the approach taken by large animals — mammals — today."

Many mammal, including humans, have teeth that are firmly fixed in the jaw for life after losing their milk teeth.

Reptiles and many fish, however, grow replacement teeth to continually replace them through their lives.

Dr D'Emic and his colleagues, whose work is published in the journal PLOS One, examined fossilised tooth sockets of a number of sauropod dinosaurs.

Dental histology of the sauropod dinosaurs Camarasaurus and Diplodocus. Thin sections of Camarasaurus (A, C) and Diplodocus (B, D) premaxillary teeth showing incremental lines of von Ebner (white arrowheads) in dentin

Using CT scanning technology, they found that Diplodocus had up to five replacement teeth behind the functional tooth in each socket.

The distantly related Camarasaurus had three replacement teeth in each socket.

By counting the layers of dentine that built up in the teeth they were able to estimate the rate at which the teeth grew and so how often they were replaced.

Diplodocus replaced a tooth once every 35 days while Camarasaurus replaced them once every 62 days.

Another herbivorous dinosaur, the 29 foot long Nigersaurus, is thought to have replaced its teeth once every 15 days or so.

The differences between the teeth replacement rates suggests different feeding strategies and food, the scientists said.

Dr D'Emic said: "Tooth replacement rate, size, and shape data indicate that despite their somewhat stereotyped body plan and large body size, sauropod dinosaurs exhibited varied approaches to feeding.

"The coexisting but morphologically disparate and distantly related Late Jurassic sauropods Camarasaurus and Diplodocus differed greatly in their anatomy related to food acquisition."

He added that growing lots of small teeth and replacing them regularly probably required a lot less energy than growing large, hard wearing teeth.


"Replacing a tooth every month reduces the number of excessively worn crowns in the functional dentition, which prolongs contact with opposing teeth and with food."

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