While reading the SVP 2010 abstract book, I came upon an abstract by Ridgwell and Sereno (2010) discussing a non-stegosaurian, non-ankylosaurian, thyreophoran from the Jurassic Tiouaren Formation of Niger. As described by Ridgwell and Sereno, the Tiouaren thyreophoran possesses armor of various forms, including spikes, ankylosaur scutes and stegosaurian plates. Since the Tiouaren thyreophoran is more primitive than Eurypoda, how does this species shed light on the origins of stegosaur and ankylosaur armor?
Ridgwell, N., and Sereno, P., 2010, A basal thyreophoran (Dinosauria, Ornithischia) from the Tiouraren Formation of Niger: In: 70th anniversary meeting of the Society of Vertebrate Paleontology, Program and Abstracts, p. 150a-151a.