Sauropod Armor is Not Something Frequently Referenced
The sauropods, known for their huge size and extremely long necks and tails on a stout body, aren’t instantly associated with having armor like the Ankylosaurs. It has always been thought that the huge size of the sauropods kept these herbivores safe from predators, but how much do we really know about these supposedly gentle giants?
Sauropod Armor is Not Unheard Of
Many Sauropods have been discovered to have rather odd looking bony ornamentation on their backs and many had the weapon of their long and heavy whip-tail. Shunosaurus had a club on the end of its tail, Amargasaurus had mysterious double rows of neck spines, Agustinia, the most ornately decorated sauropod, had a double-row of spiky knobs whilst Saltasaurus had a mosaic of scutes (a thick bony plate on the back similar to that of a modern-day crocodile).
Sauropod Armor Leaves Unanswered Questions
Sauropods within the subgroup titanosaur had osteoderms – bones embedded within their skin. These it is thought would have strengthened their hides against attack but they still pose unanswered questions. Why were they needed? Was is truly armor or just decoration used in mating rituals?
Was Sauropod Armor for Juvenile Defense?
We often overlook something when discussing these giant dinosaurs – Juvenile Sauropods. We automatically think of the sauropods as being huge and able to protect themselves due to their size, but they had to grow and develop from considerably smaller eggs. These juveniles would have needed to be able to protect themselves from predators somehow, especially as female sauropods were not known to look after their young. It is quite possible that the over-looked and obsolete bony ornamentation and armor in adults was of vital importance in protecting young sauropods.
Sauropod Armor Scutes Had Little Defensive Function
Palaeontologist know that the scutes in adults would have had little function in defense as they were set too far apart to offer any protection, but in the young titanosaur these bony scutes along the back would have been closer together only growing further apart as the dinosaur grew. It’s not known exactly how the scutes in young would have been used, their neck and undersides still being vulnerable to attack, though one theory is that they were used to discourage insects and parasites from attacking and attaching themselves to the back area.
New Theories on Sauropod Armor
A new theory has recently come to light in a report by palaeontologist Kristina Curry Rogers that shows how the use of osteoderms may have changed as the dinosaur grew. Osteoderms seen in other animals are known to have a dense outer layer of bone surrounded by spongy bone inside and this corresponds with the osteoderm found near a juvenile Rapetosaurus which would have used these special bones against attack. But when palaeontologists used CT-scanning to look inside a large osteoderm measuring 22 inches long which was found near an adult Rapetosaurus they found something unusual. They discovered that the inside of this osteoderm was mostly hollow and that the thickness of the outer later of bone varied around the internal cavity. The microscopic bone structure inside the osteoderm showed signs that bone was being absorbed into the body.
This discovery has lead Kristina Curry Rogers and her colleagues to think that osteoderms in adult dinosaurs were not used as armor, since a hollow bone would be rather useless in protection plus it was not needed due to their size. So instead the sauropod armor became a sort of a mineral reservoir, drawn upon in times when extra calcium or phosphorous minerals were needed such as when females laid eggs (calcium being needed to form the hard outer shell) or for when individuals were living in arid conditions.