GEOL 104 Dinosaurs: A Natural History

Fall Semester 2006
Thyreophora: Defense! Defense! Defense!

Thyreophora ("shield bearer"):

  • Armored dinosaurs: diagnosed by presence of rows of dermal ossifications
  • Early thyreophorans small (1 m long) bipedal animals; later forms much larger and quadrupedal, with heavier armor

    Best known early of these is small bipedal Scutellosaurus (Early Jurassic, North America).

    Scelidosaurus (Early Jurassic, Europe (maybe North America, China). Larger than Scutellosaurus, about 4 m long. Armor was proportionately much larger. Heavy armor required it to be an obligate quadruped. May actually be the basalmost ankylosaur.

    Thyreophorans more derived than Scelidosaurus are divided into two major branches:

    Both appear in the Middle Jurassic, just as more sophisticated predators are appearing.



    Ankylosaurs include the Nodosauridae (characterized by an expanded process on the scapula) and the highly derived Ankylosauridae. Definite nodosaurids are known from the Cretaceous of North America and Europe. Various Late Jurassic and Early Cretaceous ankylosaurs have been placed at the base of either Nodosauridae and Ankylosauridae, although some have proposed a third clade: the "polacanthids".

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    Last modified: 14 July 2006