Kentrosaurus: Prehistoric Animal of the Week

Kentrosaurus aethiopicus was a plant eating dinosaur that lived in what is now Tanzania, Africa during the Late Jurassic Period, 150 to 155 million years ago.  It wasn't terribly large for a dinosaur, only measuring about sixteen feet long from head to tail.  Like its close relative, Stegosaurus, it was adorned with spikes on its tail for defense.  Unlike Stegosaurus, however, the spikes on Kentrosaurus didn't stop there!

Kentrosaurus aethiopicus life restoration by Christopher DiPiazza

 The name Kentrosaurus literally translates to "Prickly lizard/reptile" and boy, was it prickly!  The neck probably had small plates, as in its relative, Stegosaurus, but on the body the shapes of the plates quickly change to broad spikes.  From the hip on towards the tail were rows of narrower, sharp spikes.  The plates and spikes of Kentrosaurus were what is called "handed", i.e., there are left and right versions of them so it is likely they were arranged in two rows down the animal's back.  Additionally there is another kind of spike found with Kentrosaurus that doesn't fit on the back or tail anywhere.  Scientists either think these spikes were on the shoulders or the hips (depending on which scientist you ask).  As in all stegosaurids, the head of Kentrosaurus was tiny in proportion to the rest of the body and possessed a beak at the front of the snout.  Inside the mouth were teeth adapted for crushing plant material but could not finely grind.

Kentrosaurus skeletal mount at the Museum fur Naturkunde in Berlin, Germany.

 Kentrosaurus, like other stegosaurids, is interesting in that its center of gravity was at the hips, farther back towards the tail end than what is normally observed with quadropeds (animals that walk on all fours).  In fact, no other kind of dinosaur has its center of gravity as far back as the stegosaurids.  This allows the animal's front half where the head and arms are to be much lighter.  There would be a number of possible advantages to this.  Firstly, stegosaurids like Kentrosaurus may have had the ability to rear up on their hind legs in order to gain access to more food.  Secondly, being lighter in the front meant the animal could rotate its body sideways more easily.  Since Kentrosaurus'  weapon was its tail, this would allow it to make fast turns to ensure its dangerous end was always facing an attacker.  A study by paleontologist Heinrich Mallison concluded that Kentrosaurus had a pretty wide range of motions when it came to its neck, legs and tail.  It was found that the tail in particular could swing in a 180 degree arc with deadly accuracy if it needed to, delivering deadly blows with the tail spikes.  

Diagram showing range of motion for Kentrosaurus's tail from Heinrich Mallison's study.

Special thanks to Dr. Heinrich Mallison for allowing me to use one of his images and for coaching me on my illustration and information for this week's post!  As always if you would like a particular creature to be reviewed and illustrated simply comment below or on our facebook page! 

References

Hennig, E. (1936). "Ein Dentale von Kentrurosaurus aethiopicus HENNIG" ("A dentary of Kentrurosaurus aethiopcius HENNIG"). Palaeontographica Supplement 7 Part II':311-312 German

Mallison, H. (2010). "CAD assessment of the posture and range of motion of Kentrosaurus aethiopicus HENNIG 1915" Swiss Journal of Geosciences online first

Mallison, H. (subm.). "Defense capabilities of Kentrosaurus aethiopicus HENNIG 1915. Palaeontologia Electronica