Chapter 7 Outline

INTRODUCTION TO ANKYLOSAURIA (FUSED LIZARD)

• CHARACTERISTICS
  • BONY PLATES AND SPINES EMBEDDED IN THE SKIN AND INTERLOCKED WITH ADJACENT PLATES FORMING A CONTINUOUS SHIELD ACROSS THE NECK, THROAT, BACK AND TAIL, AND ALSO COVERING THE TOP OF THE HEAD AND OFTEN THE CHEEKS
  • QUADRAPEDAL LIMB POSTURE
  • LOW, BROAD HEADS WITH SIMPLE, LEAF-SHAPED TEETH THAT SUGGEST ANKYLOSAURS WERE HERBIVORES
  • BODY WAS ROUND AND BROAD AND PROBABLY HOUSED A LARGE GUT
  • SHORT LIMBS WITH HINDLIMB LENGTHS EXCEEDING FORELIMB LENGTHS BY 50%
    • Toes ended in broad hooves
  • RARELY LONGER THAN FIVE METERS, ALTHOUGH SOME REACHED NINE METERS IN LENGTH
  • WEIGHTS WERE UP TO 3500 KILOGRAMS
• GEOLOGICAL RANGE & DIVERSITY
  • MIDDLE JURASSIC TO LATE CRETACEOUS (~175 - 65 MILLION YEARS)
  • MAXIMUM DIVERSITY - AT LEAST 9 GENERA DURING THE LATE CRETACEOUS
    • At least 20 genera (25 species) throughout their time on earth
    • But 6 or 7 genera are known only fragmentary skeletal remains
  • FOUND IN NORTH AMERICA, EUROPE, MONGOLIA, CHINA AND AUSTRALIA

HISTORY OF ANKYLOSAUR DISCOVERIES

• 19TH CENTURY
  • EUROPE
    • 5 genera from middle Jurassic, and early & late Cretaceous beds
    • Hylaeosaurus - one of the three original members of Owen's Dinosauria
  • NORTH AMERICA
    • 1 genus from early Cretaceous beds
• 20TH CENTURY
  • NORTH AMERICA
    • 7 genera from early & late Cretaceous beds (1902-1928, 1960's, 1970's)
    • Ankylosaurus & Euoplocephalus
  • MONGOLIA & CHINA
    • 6 or 7 genera from early & late Cretaceous beds (1920's, 1960's, 1970's)
  • EUROPE
    • 1 genus from late Jurassic beds (1980)
  • AUSTRALIA
    • 1 genus from early Cretaceous beds (1980)

ANKYLOSAUR DIVERSITY

• TWO CLADES OF ANKYLOSAURS - ANKYLOSAURIDAE AND NODOSAURIDAE
  • DIFFERENTIATED BASED ON PRESENCE (ANKYLOSAURIDAE) OR ABSENCE (NODOSAURIDAE) OF A TAIL CLUB

ANKYLOSAUR PALEOBIOLOGY AND PALEOECOLOGY

• SKELETAL CONDITIONS
  • ANKYLOSAUR SKELETONS FROM ASIA ARE NEARLY COMPLETE & ARTICULATED, SOMETIMES PRESERVED IN UPRIGHT POSES OR ON THEIR SIDES
  • THOSE FROM NORTH AMERICA ARE ONLY PARTIAL SKELETONS & OFTEN FOUND UPSIDE DOWN, SOMETIMES IN TRANSITIONAL OR MARINE SEDIMENTARY BEDS
    • Suggests bloated carcasses floating upside down from weight of armour
• BEHAVIOUR
  • ANKYLOSAUR SOCIAL BEHAVIOUR MOSTLY UNKNOWN
    • Generally only individual skeletons or isolated remains are found
    • Pinacosaurus may have lived in herds
      • TWELVE SPECIMENS IN AN ACCUMULATION IN CHINA
• EATING
  • ANKYLOSAURS WERE LOW-BROWSERS (less than 1 meter)
  • ANKYLOSAURS, LIKE STEGOSAURS, HAVE A MIX OF CHARACTERISTICS, SOME OF WHICH SUGGEST SOPHISTICATED ORAL FOOD PROCESSING AND OTHERS OF WHICH SUGGEST SIMPLE ORAL FOOD PROCESSING COMBINED WITH INTERNAL FOOD BREAKUP
    • Sophisticated oral food processing
      • SCOOP-SHAPED BEAKS
        • Narrower in nodosaurids; wider in ankylosaurids
        • Nodosaurids may have been more selective in foliage or fruit choice
      • WELL-DEVELOPED, DEEP CHEEK POUCHES
      • LONG, FLEXIBLE TONGUES
        • Large hyoid bones
      • JAW BONES THAT WERE LARGE AND STRONG
        • Jaw muscles seem to be weak, however
      • HAD SECONDARY PALATES THAT APPARENTLY ALLOWED THEM TO BREATH & CHEW AT THE SAME TIME
    • Simple oral food processing combined with internal food breakup
      • TEETH ARE RELATIVELY SMALL, SIMPLE, AND TRIANGULAR AND APPARENTLY DID LITTLE GRINDING (LACK WELL-DEVELOPED WEAR SURFACES ON CROWNS) AND
      • ANKYLOSAURS HAD A HUGE ABDOMINAL CAVITY
        • May have housed differentiated fermentation chamber
  • NOTE - ANKYLOSAURIDS HAD CURVED THIN BONES WITHIN THEIR NASAL PASSAGES SIMILAR TO THOSE OF BIRDS & MAMMALS (lined with membranes to filter, warm & moisten incoming air and retain moisture & warm from outgoing air)
• BRAINS
  • ANKYLOSAURS HAD SMALL BRAINS (even smaller than Stegosaurs)
    • Relatively large olfactory bulbs suggest Ankylosaurs had a good sense of smell
• DEFENSIVE MOVES
  • CALCULATIONS BASED ON LIMB SIZE AND BODY MASS SUGGESTS THAT ANKYLOSAURS WERE SLOW
    • Running - <10 km/hr; walking - ~3 km/hr
    • They were probably quite agile when attacked by predators, however
  • HUNKERING DOWN AND/OR TAIL-CLUBBING
    • Ankylosaurs were covered with bony armor
      • WITH LEGS FOLDED UNDER BODY, AN ANKYLOSAUR WOULD HAVE BEEN DIFFICULT TO FLIP OVER
    • Nodosaurids had shoulder spines and massive shoulder muscles
      • PLANTED REAR LEGS AND ROTATED THEIR FOREQUARTERS TO PRESENT SPINES TOWARD PREDATOR
    • Ankylosaurids had a massive tail club
      • FRONT HALF OF TAIL WAS FLEXIBLE, BUT THE REAR HALF WAS STIFFENED BY MODIFIED VERTEBRAE AND LONGITUDINALLY RUNNING TENDONS
      • POTENT THREAT TO THE LEGS OF A T. REX
        

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