Does fumaric acid form maleic anhydride upon heating?
Fumaric acid does form maleic anhydride due to partial combustion. From wikipedia article of fumaric acid:


  Fumaric acid converts to the irritant maleic anhydride, upon partial
  combustion.


Also, dehydrating fumaric acid with a  dehydrating agent also forms maleic anhydride. This paper describe how to convert $\ce{C^{14}}$ labelled fumaric acid to maleic anhydride.


  Maleic anhydride-2-$\ce{C^{14}}$ is readily obtained from fumaric
  acid-2-$\ce{C^{14}}$ through dehydration using phosphorus pentoxide
  getting 96% yield under controlled condition.