BIO2242 Lecture Notes - Lecture 22: Hadrosaurid, Ornithischia, Saurischia
Lecture 22 – Dinosaur Form and Function
What were Dinosaurs?
• Archosaurian diapsid reptiles
o Ancient lizards
o Subgroup of reptiles
• All had upright posture
o Legs directly under body – don’t sprawl out to side
• Limbs moved parallel to long axis
• Dominated terrestrial environment from late
o Triassic 150 million years ago to end of Cretaceous 65 mya
• Divided into Ornithischia (bird-hipped) and Saurischia (lizard-hipped) on
basis of pelvis morphology
• Ornithischia: herbivorous dinosaurs, hadrosaurs, ceratopsians, armoured
dinosaurs
• Saurischia: giant sauropods (2 legs) and therapods
• If pelvic bone forward – all legs can be underneath it
Fossils
• Key to reconstruction
• Preserve hard structures
• Covered by sediment over periods of time → rock solidifies and becomes
crystals → crystals formed from bone
• Body and trace fossils
o Evidence of presence of animal (trace)
▪ Skin impression
• Scales – tells us function
▪ Presence of eggs
▪ Footprint: width and number of toes/presence of claws
• Stride – length of step → stride
o Body – actual skeleton itself
Locomotion
• Obligate bipeds (e.g. raptors)
o Arrangement of legs directly under body to maintain balance
o Long flexible tail to counterbalance
o Small front limbs/forelegs so head can be larger
• Facultative bipeds (e.g. hadrosaurs)
o Move around on 4 limbs – get up on 2
o A lot of ossified tendons
o Grazers
• Obligate quadrupeds (e.g. sauropods)
o Move around on 4 limbs all the time
o Always 3 limbs on ground at the same time – life elephant. Very heavy
o Largest dinosaurs
o Bones of legs doing support, not muscle
Feeding
• Diet inferred from teeth, skull and size
find more resources at oneclass.com
find more resources at oneclass.com
