Nodosaurus

Name: Nodosaurus ‭(‬Knobbled lizard‭)‬.
Phonetic: No-doe-sore-us.
Named By: Othniel Charles Marsh‭ ‬-‭ ‬1889.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Dinosauria,‭ ‬Ornithischia,‭ ‬Thyreophoroidea,‭ ‬Ankylosauria,‭ ‬Nodosauridae.
Species: N.‭ ‬textilis‭ (‬type‭)‬.
Diet: Herbivore.
Size: Estimated between‭ ‬4‭ ‬and‭ ‬6‭ ‬meters long.
Known locations: USA,‭ ‬Wyoming‭ & ‬Kansas.‭
Time period: Late Cretaceous.
Fossil representation: 2‭ ‬individuals represented by partial remains.‭ ‬Additional armour scutes.

       Just like with Ankylosaurus,‭ ‬Nodosaurus is the type genus of a whole group of armoured dinosaurs,‭ ‬yet it is also one of the most poorly represented by fossil material.‭ ‬The nodosaurids are thought to be the ancestors of the ankylosaurids,‭ ‬although to have continued to thrive even in the presence of their more heavily armoured relations.‭ ‬The obvious similarity between nodosaurids and ankylosaurids is the small pieces of bony armour‭ (‬referred to as osteoderms,‭ ‬but also called scutes‭) ‬that ran across the back and upper flanks of the body.‭ ‬Key differences include however a lack of a clubbed tail,‭ ‬a narrower mouth,‭ ‬and the lack of a more advanced nasal system that appears to be characteristic of the more advanced ankylosaurids.
       Although an exact size for Nodosaurus currently remains hard to establish,‭ ‬the fossil material at least indicates that Nodosaurus was a medium to large sized nodosaurid.‭ ‬The osteoderms than ran across its back were rectangular in individual appearance and arranged in bands that ran down towards the sides.‭ ‬These osteoderms did not extend to the belly however,‭ ‬and if a large predatory theropod like a tyrannosaur managed to flip a Nodosaurus over it would be completely defenceless.‭ ‬The additional armour along its back meant that the legs of Nodosaurus had to become strong enough to accommodate the extra weight,‭ ‬and to facilitate this they became short and squat with attachments for stronger muscles.‭ ‬As such the additional weight and shorter stride of Nodosaurus meant that it could not rely upon speed and agility to escape predators,‭ ‬which has led to the idea that Nodosaurus,‭ ‬as well as other nodosaurids,‭ ‬may have collapsed to the ground to try an prevent a large theropod the chance to work its foot under the body and flip it over into its back.‭
       This meant that only the armoured back was presented to attackers,‭ ‬although it is debateable how effective a defence this would have actually been.‭ ‬In the west tyrannosaurids like Daspletosaurus seem to have been well suited to crunching through tough prey,‭ ‬while in the east Appalachiosaurus seems to have been more gracile,‭ ‬but possibly could have approached other large tyrannosaurids in size.‭ ‬You also have to consider that if this defence actually worked,‭ ‬there would have been no need for the later ankylosaurids to evolve special spikes around the back of their heads,‭ ‬an area that is surprisingly under protected in many nodosaurids.‭ ‬It is possible that while attack from a large tyrannosaur could have easily meant the end for Nodosaurus,‭ ‬such predators were not as numerous as smaller theropods such as Dromaeosaurus,‭ ‬that would have more easily been defeated by the armour while being physically incapable of flipping a Nodosaurus onto its back.

Further reading
Notice of gigantic horned Dinosauria from the Cretaceous. American Journal of Science 38:173-175. - Othniel Charles Marsh - 1889.



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