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
- 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