1. GEOL 240 The Dinosaurs: Thyreophora

2. What is a Thyrephora

3. Thyreophora z“shield bearer” zArmored dinosaurs diagnosed by the presence of rows of dermal ossification yPrimitive Thyreophora yStegosauria yAnkylosauridae

4. Thyreophoran Cladistics

5. Lateral Side Dorsal SideVentral Side Lateral Side 1 cm Thyreophoran Armor Plates

6. Stegosaurus Restoration Thyreophoran Dinosaurs

7. “Primitive” Thyreophora z First fossil thyreophorans small (1 m long) bipedal animals; later forms much larger and quadrupedal, with heavier armor z Best known of these is small bipedal Scutellosaurus (Early Jurassic, North America).

8. Relatively small (1.2 meters long) “generalized” ornithischian however, Scutellosaurus, had an extensive body covering of bony plates set in the skin. “Primitive” Thyreophora

9. Primitive Thyreophora Skeletal disposition of Scutellosaurus (Lower Jurassic, Arizona).

10. “Primitive” Thyreophora z Scelidosaurus (Lower Jurassic, England (maybe North America, China). Larger than Scutellosaurus, about 4 m long. Armor was proportionately much larger. Heavy armor probably required it to be an obligate quadruped.

11. small head with leaf-shaped teeth which run to the snout, massive limbs of nearly equal length, no armor on skull but its back was covered with numerous bony plates broad sacrum Scelidosaurus

12. “Primitive” Thyreophora z Skeletal disposition of Scelidosaurus (Lower Jurassic, England (maybe North America, China).

13. Huayangosaurus zmost primitive stegosaur zfrom middle Jurassic of China z4.3 meter-long zspike-shaped armor along the midline of the body and additional rows of small armor plates along each side of the row of spikes

14. Thyreophoran Cladistics

15. Huayangosaurus

16. 50 cm Huayangosaurus

17. Stegosauridae zAll stegosaurus other than Huayangosaurus zlow skulls (distance between eyes greater than depth of skull) zlong snout zposterially located eye sockets zlarger size zmassive zrelatively long hind limbs

18. Stegosauria z“Plated-lizards” zmedium sized (up to 9 meters long) zquadruped zherbivorous zsmall heads zshort massive forelimbs zlong, columnar hind limbs zshort stout feet with hooves

19. Stegosauria zUnique features yvertical bony plates and pines arranged in single or double rows along the neck, back and tail zStegosauria - May be defined as all thyreophoran ornithischians more similar to Stegosaurus than to Ankylosaurus.

20. Stegosauria zHowever, some scutes become much larger and highly specialized: oPlates (flat sided) and Spines (round cross- section) in pairs down the the back (derived stegosaurs such as Late Jurassic North American Stegosaurus had alternating plates rather than pairs) oShoulder spines in the more primitive forms oThagomizers (pairs of laterally facing spines) on the end of the tail, used as an active defense, swung from side to side

21. Stegosauria zFirst appear as fossils in Middle Jurassic, common in Middle and Upper Jurassic, rare in Lower Cretaceous, last appearance at or before Lower-Upper Cretaceous boundary zReduce the size of most of the scutes on the body relative to Scelidosaurus scute - A horny, chitinous, or bony external plate or scale

22. Stegosauria

24. 50 cm Stegosaurus Stegosauridae

25. 50 cm Tuojiangosaurus Kentrosaurus Stegosauridae

26. Stegosaurus zhad only a midline row of armor plates zvery small head ztip of snout formed narrow toothless beak zcheek teeth leaf-shaped zno dental battery zlong neck and tail zbig shoulder blades

27. Stegosaurus zpossible semi-sprawling posture with front limbs zforelimb had five short broad toes with hoof-like tips zhind limb extremely long and pillar-like zhind limb had three toes with hooves

28. Stegosaurus znumerous small knob-like plates distributed over skin of most of the body zprominent plates along backbone ztwo pairs of spikes located on tail

29. Stegosauridae

30. Stegosaurus

32. 20 cm Stegosaurus Plates Stegosauridae

33. Stegosaurus

34. Ankylosauria

35. 1 m Euplocephalus - Ankylosaurid Nodosaurus - Nodosaurid Ankylosauria

36. 50 cm Polacanthus - Nodosauridae Nodosauridae

37. Ankylosauria z“fused lizards” zrod of fused vertebrae in their backs zmedium-sized (up to 9 meters) zquadruped zplant-eating

38. zsmall heads zleaf-shaped teeth znon-interlocking teeth (not occluding) zbroadly arched ribs - very wide body zbody covered in small round or square armor plates zsome had spikes or spines zsome had a tail club zforelimbs about 2/3 to 3/4 the length of the hind limbs Ankylosauria

39. zAlso first appear in Middle Jurassic, are present but rare in Late Jurassic, but become extremely common in Cretaceous Ankylosauria

40. zLow skulls zhoofed toes zlow skull zAre more heavily armored than Scelidosaurus including: oScutes fused directly to skull roof oRings of fused scutes on neck and front of shoulders oFused scutes over hip region oLaterally-facing spines in all but the most advanced forms oclosure of fenestra in front of orbit and on top of skull Ankylosauria

41. zAre more heavily armored than Scelidosaurus including: oSmall triangular hornlets sticking out from the rear of the dorsal surface of the skull oLarge shoulder spines in some forms oScutes down arms, and even over eyelids and cheeks of some species! oWere most likely passive defenders: hunker down and absorb attacks (although probably pushed back with their spine as well) yAnkylosaur hips are very wide, and the ilia flare out to form shelf Ankylosauria

44. z Ankylosaurs have been divided into two clades: Nodosauridae and Ankylosauridae. However, "nodosaurids" as traditionally imagined are a paraphyletic grade. Ankylosauria

45. "nodosaurid" zHylaeosaurus is an Early Cretaceous European "nodosaurid"; Edmontonia is a Late Cretaceous North American one zDistinguished by narrow skulls which lacked armor and horns, presence of spines in their armor and the lack of ossified tail tendons or a tail club

46. Ankylosauridae

47. oCharacterized by shorter, deeper, triangular skulls with small triangular hornlets sticking out of the ventral surface of the back and by complex nasal passageways oGastonia is an Early Cretaceous North American primitive ankylosaurid

48. Ankylosauridae oThe most sophisticated ankylosaurids were the Ankylosaurinae of the mid-Cretaceous of Asia and the Upper Cretaceous of Asia and western North America oDeveloped a bony tail club for active defense against predators (tyrannosaurids) oAnkylosaurus is an ankylosaurine, and the largest ankylosaurine, ankylosaurid, ankylosaur, and one of the largest thyreophorans (are some very large stegosaurs, too)

49. 10 cm Tail Club of Ankylosaurids Ankylosaurid Weapons?

50. Ankylosauridae