# Size

Sauropods came in different sizes--most of them big. An adult female Mamenchisaurus would have weighed about 13 tons (12,000 kilograms). That may sound big, but it's actually below average for sauropods.

One of the very largest, the huge Argentinosaurus, may have grown to 90 tons (82,000 kilograms)! Argentinosaurus was almost 10 times bigger than the largest known land mammals. But surprisingly, some dwarf sauropod species weighed less than one ton, or about as much as a modern rhino.

##### Island Living

Animals that live on islands are sometimes much smaller than their close relatives living elsewhere--a phenomenon called island dwarfism. Species of dwarf sauropods like Europasaurus holgeri lived on islands in what is now Europe.

##### Biggest of the Big

The sauropod group included the largest land animals ever, and many of the biggest sauropods belonged to the group known as titanosaurs (tie-TAN-uh-SAWR). Some of the very biggest titanosaurs have been found in South America--including Argentinosaurus, which could reach 90 tons (82,000 kilograms). Titanosaur fossils have been found on every continent except Antarctica.

Paleontologists can measure the length of a fossilized thigh bone from a sauropod to determine what the dinosaur weighed when it was alive. What if a sauropod had a thigh bone as long as yours? How heavy do you think that dinosaur would have been? Remember, sauropods and humans are built very differently. Try it yourself!

Step 1: Measure

Measure the distance in centimeters between your knee and your hip joint--that's roughly the length of your thigh bone.

Step 2: Enter the length

Enter the length in centimeters.

Step 3: Calculate

Here's how much a sauropod with a thigh bone the length of yours would have weighed: __________

##### How big?

Check out the weights of the modern-day animals below to get a sense of just how heavy a sauropod with a femur as long as yours would have been.

Sheep 110 lbs (50 kg)
Grizzly Bear 770 lbs (350 kg)
African Elephant 12,000 lbs (5,500 kg)