Thyreophora


Ankylosaurus magniventris by Todd Marshall (2004)
CHARACTERS

  • Best known for their dermal armour, spines, shields, and clubs found all over their body in various distributions
  • Early forms were bipedal, but later, more derived animals were completely quadrupedal
  • Broad elephantine feet that had toes that would spread to compensate for the heavy weight of the animal and its dermal armour
  • Small interlocking plates in some forms
  • Broad, flattened skull
  • Tibia (shin bone) is shorter than the femur (thigh bone)


Cladogram provided courtesy of T. Holtz Jr 2004 (http://www.geol.umd.edu/~tholtz/G104/10418thyr.htm)

THYREOPHORA "shield bearer" (2)

(1) STEGOSAURIA (2)

Stegosaurs first appeared during the Middle Jurassic and died out during the Early Cretaceous, although Cretaceous forms are rare. Scute size varied in the different forms, and some became huge and very specialized. Stegosaurus, the most famous stegosaur, has rows of huge plates running down its back that have been the focus of debate for years. Some palaeontologists believe they were for sexual display, others for thermoregulation, or even protection.

(1) STEGOSAURIDAE

  • The armour on the back was in large flattened plates (example: Stegosaurus stenops)

(2) KENTROSAURIDAE

  • The armour on the back was in plates hear the head, but progessively turned into spines going backwards (Examples: Kentrosaurus, Huayangosaurus)

Stegosaurus stenops by Todd Marshall (2004)

(2) ANKYLOSAURS (3)

Like the stegosaurs, ankylosaurs became common during the Jurassic, and they increased in number and thrived right to the end of the Cretaceous. These animals are defined as being more heavily armoured than Scelidosaurus.

CHARACTERISTICS

  1. (1) NODOSAURIDAE - Example: Edmontonia

  2. (2) POLACANTHIDAE - These Ankylosaurs had head with a downward pointing snout. Example : Hylaeosaurus, Pawpawsaurus, Panoplosaurus

  3. (3) ANKYLOSAURIDAE - This group the most derived of all the Ankylosaurs, and contained the largest species Ankylosaurus. They lived from the Middle to Late Cretaceous of North American and Asia

    • Small triagular skulls covered in scutes and tiny horns
    • Nasal passages were extremely well developed
    • Presence of a large defensice club at the end of the tail made of bone

Ankylosaurus without armour, by P. Olsen (2004)

NEXT : ORNITHOPODA



Author: Emma Schachner
Last updated: 13 November 2004
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Websites produced by students on the MSc Palaeobiology programme in the Department of Earth Sciences at the University of Bristol for academic year 2003-4