Dinosaurs: Tyrannosaurus Rex and Ankylosaurus

Tyrannosaurus Rex

• Lived during the end of the Cretaceous period
• Largest theropod and biggest known land carnivore
• Preyed on various contemporaries such as Triceratops and Hadrosaurus
• Known for causing damage to many coexisting animals

Ankylosaurus

Discovery and Classification

• Discovered in the early 1900s in Hell Creek formation, Montana, USA
• Mix of bones, teeth, and osteoderms found
• Named Ankylosaurus (fused lizard)
• Holotype named Magniventris (great belly)
• Creation of new group: Ankylosauria
• Defined by herbivorous, armored dinosaurs with fused bony shields

Physical Characteristics

• Largest known ankylosaur: length 5.4-10m, height 1.7m at hips
• Weight: 5-8 tons
• Robust body, short broad bones, and extensive bony armor
• Armor composed of osteoderms, which were thinner and hollow underneath
• Collagen fibers under armor for force distribution and shock absorption

Defense Mechanisms

• Tail club made of osteoderms: width 57 cm, weight 50 lbs
• Significant striking force: up to 20,000 Newtons
• Debate about tail club usage: defense or social dominance?
• Juveniles: poorly formed armor and tail clubs, grouped together for protection
• Adults: solitary, heavily defended

Diet and Digestion

• Herbivorous: ate ferns, shrubs, possibly fruit and invertebrates
• Teeth: cusp-like, for cutting vegetation
• Narrow beak for stripping leaves
• Digestive system with hindgut fermentation (similar to rhinos)
• Daily food intake: about 60 kg
• Broad midsection for fermentation vat
• Excellent sense of smell for detecting food and predators

Habitat and Coexisting Species

• Lived in northwestern America and Alberta, Canada
• Preferred forested flood plains with subtropical climates
• Coexisted with multiple species: Triceratops, Edmontosaurus, Dakotaraptor, etc.
• Lived in a diverse ecosystem with large river systems and varied flora and fauna

Extinction

• Lived from 68 to 66 million years ago
• Low population density (only 1% of Hell Creek finds)
• KT Extinction event: asteroid impact likely caused rapid-moving fires leading to demise