• Sara Thompson

Dinosaurs Keep Getting Bigger

By Sara Thompson

Special to the Enterprise

Argentinosaurus in Fernbanks Museum of Natural History; Photo by Jeremy Thompson from Wikimedia Commons.

The long-necked sauropods are some of the most recognized dinosaurs of all time. These behemoths begin appearing in the fossil record around the late Triassic and early Jurassic periods. By the mid and late Jurassic sauropods would have diversified into dozens of species and spread onto every continent, even Antarctica! Sauropod diversity peaked in the Jurassic, but these enormous animals would continue to live and thrive until the end of the Cretaceous, going extinct at the same time as the rest of the dinosaurs.

Sauropods are easily the largest animals to ever walk the earth. One of the smallest sauropods was the Ohmdenosaurus which was only about 13 feet long and 6 feet tall. Current thinking is that Argentinosaurus was the longest sauropod at around 115 feet long, and also the heaviest at an estimated 65-80 metric tons. The tallest, however, is currently Barosaurus which stood about 72 feet tall. Several factors went into their enormous size including the hollowing of their bones, inclusion of air sacks into their skeletons, and the ability to eat large quantities of food at once.

The hind feet of sauropods were both wide and long and the fore feet of sauropods were smaller and had a horseshoe shape. Even though the fore feet were smaller, the rest of the limbs were built for incredible weight bearing. Unlike modern animals, sauropods did not have a fleshy pad on their feet to help, as evidence from trackways found all over the earth.

One thing that helped the sauropods to support their own weight is having hollow bones. Much like birds, these animals shed excess weight by lightening their bones. There is also evidence in almost all species of sauropods of air sacks in their skeletons, indicated by indentations and hollowed spaces throughout the skeletal body.

How sauropods held their heads and neck is still up for debate and may not have been standard across all the species. Many species of sauropods had forelimbs shorter or equal to the length of their hindlimbs and is currently accepted that they held their heads and necks horizontally. This would reduce the energy needed to get blood to the head. Brachiosaurids might have held their heads and necks upright since their forelimbs were longer than their hindlimbs. The difference in head and neck posture, as well as varying teeth shapes indicates that different species of sauropods ate at different vegetation levels or different plants all together. This made it possible for multiple species to live in the same ecosystem and not compete for resources.

Sauropod teeth were not built for chewing and evidence of stones being swallowed to aid in digestion suggests that sauropods might not have chewed their food much, but rather swallowed it whole. By reducing the energy needed to chew and digestion, sauropods could instead use that energy to reach their massive sizes.

Like all dinosaurs, there is still much to discover about sauropods. Paleontologists are constantly finding new specimens to study or using better technology and techniques in interpreting the fossil record. We will never truly know how these animals lived or how they got to be so super-sized, but they will continue to inspire and fascinate scientists of all ages.

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