Nov
04
2011

Sauropod teeth show evidence of migration

Teeth tell tales of travel: Ratio of oxygen isotopes in Camarasaurus teeth reveals that the sauropod migrated long distances to find food and water. Geological Museum, University of Wyoming, Laramie, WY
Teeth tell tales of travel: Ratio of oxygen isotopes in Camarasaurus teeth reveals that the sauropod migrated long distances to find food and water. Geological Museum, University of Wyoming, Laramie, WYCourtesy Mark Ryan
Ever wonder how something as big as a sauropod dinosaur was able to grow so large? Sauropods were those huge, long-necked quadrupeds estimated to have weighed anywhere from 50 to 120 tons, and with lengths of up to 200 feet. Just seeing the skeleton of any one of them – the Apatosaurus, Diplodocus, Brachiosaurus, Ultrasaurus or any their kind – you just know those Jurassic giants had to be on a constant eating binge to maintain their massive size. But just how much food could a single area supply? Doesn’t it make sense that these critters would have eaten up any food source within the reach of their extensive necks? Then what would they do?

A new study of sauropod teeth has produced some strong evidence that the giant herbivores migrated during times of drought or other environmental stresses, searching for new untapped food and water sources. Geochemist Henry Fricke of Colorado College in Colorado Springs along with student colleagues Justin Hencecroth and Marie E. Hoerner studied the teeth of various Camarasaurus specimens comparing the ratio of oxygen isotopes found in the enamel with the ratio found in the sedimentary rock deposits where the teeth were found. By sauropod standards, Camarasaurus was one of the smaller ones, but it's the most common sauropod found in the Morrison Formation deposits.

Camarasaurus skeleton
Camarasaurus skeletonCourtesy Public domain
During its lifetime 145 million years or so in the past, a Camarasaurus's teeth would absorb the isotopes ratio of its environment, that is the ratio of the oxygen isotopes found in the local water supply. So Fricke’s team sampled 32 camarasaur teeth, taking measurements of the younger enamel found near the base of each tooth with the older enamel near the crown. In some cases, the isotopes ratios in the enamel matched those of the sedimentary rocks from where the teeth were found. But some enamel didn’t match. This meant the dinosaur must have migrated at some time to higher ground, more than likely in search of a better food source.

"In a theoretical sense, it's not hugely surprising,” Fricke said. “They are huge — they would probably have eaten themselves out of house and home if they stayed in one place.”

So the camarasaurs did what any hungry animal would do: they headed out in search of more food, even if it meant a migration of 200 miles into the higher regions and back. Seasonal droughts were probably another factor. The highlands would have had more rainfall and therefore more vegetation and water. When the wet season returned to the basin so would the camarasaur herds. Fricke estimates the seasonal herbivore hikes took around five months to complete. He also thinks if one kind of sauropod migrated, other genera probably did the same, and an analysis of their teeth would probably show similar results.

SOURCES and LINKS
Abstract in Nature
Nature News
Paleoclimatology: the Oxygen Balance
Camarasaurus facts

Your Comments, Thoughts, Questions, Ideas

Sharron's picture
Sharron says:

Described as 'feats of engineering', the largest sauropod dinosaurs weighed close to 100 tonnes - ten times the record weight of a modern elephant. Sauropods therefore include the largest land animals ever to have lived. They were a very successful herbivorous group, arising in the early Jurassic and surviving for around 100 million years. Fossil footprints show that sauropod dinosaurs travelled in herds. Notable sauropods include Diplodocus, Apatosaurus (formerly Brontosaurus) and the record-breaking heavyweight Argentinosaurus.

posted on Thu, 07/11/2013 - 7:05am
Kit's picture
Kit says:

5 months of hiking for food and water - no wonder they disappeared

posted on Thu, 07/11/2013 - 9:03am
Smiler's picture
Smiler says:

How can anything weighing 120 tons actually walk?!

posted on Wed, 08/14/2013 - 2:44am
Marie is awesome's picture
Marie is awesome says:

Well, a lot of that one hundred twenty tons is muscle, it will be able to hold up all of the extra weight.

posted on Thu, 08/15/2013 - 10:58am

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