Lesson 4: Moving Around Flashcards
What are the two main types of stances in vertebrates?
Sprawling stance – Limbs extend outward (e.g., lizards, crocodiles).
Erect stance – Limbs positioned under the body (e.g., birds, mammals, dinosaurs).
What are the advantages of an erect stance?
Supports weight efficiently.
Increases stride length for faster movement.
Requires less muscular effort to stand.
Did dinosaurs have a sprawling or erect stance?
Dinosaurs had an erect stance, similar to birds and mammals.
What was previously thought about Diplodocus’s stance?
It was originally depicted as sprawling, but later evidence confirmed an erect stance.
What are the three types of foot posture in animals?
Plantigrade – Walks on the full foot (e.g., humans, bears).
Digitigrade – Walks on toes (e.g., birds, theropods).
Unguligrade – Walks on hooves (e.g., horses).
What kind of foot posture did theropods have?
Digitigrade – They walked on their toes, increasing speed and agility.
Why do lizards spend most of their time resting?
A sprawling stance requires more muscle effort, making it energy-intensive to stay active.
How do mammals and birds support their weight compared to reptiles?
Their limbs are positioned directly under the body, making it easier to support weight.
What stance did early dinosaurs have?
All early dinosaurs were bipedal with an erect stance.
What types of dinosaurs became quadrupedal?
Sauropods, ceratopsians, ankylosaurs, and large ornithopods evolved quadrupedal locomotion.
What are cursorial limbs adapted for?
Fast running – they are long and lightweight.
What are graviportal limbs adapted for?
Supporting heavy body weight – they are short, thick, and sturdy.
What is a facultative biped?
An animal that normally walks on four legs but can run on two (e.g., hadrosaurs, Iguanodon).
What is an obligate biped?
An animal that always walks on two legs (e.g., theropods, small ornithopods).
How do we know Iguanodon walked on all fours?
Fossil trackways show handprints alongside footprints.
What role did the caudofemoralis muscle play in dinosaurs?
It pulled the hind leg backward, helping with powerful strides.
How did theropods’ caudofemoralis differ from hadrosaurs’?
Theropods had a high attachment, allowing for quick leg swings (useful for sprinting).
Hadrosaurs had a lower attachment, increasing endurance for long-distance movement.
What kind of locomotion did sauropods have?
They were obligate quadrupeds with graviportal limbs for weight support.
How did dinosaur tails affect their movement?
Tails acted as a counterbalance, preventing forward falls.
What do trackways suggest about dinosaur tails?
Most dinosaurs did not drag their tails, as tail-drag marks are rare.
What are ichnofossils?
Fossilized footprints, bite marks, burrows, and other activity traces.
What can dinosaur trackways tell us?
Stride length = Speed estimation.
Footprint shape = Bipedal vs. quadrupedal stance.
Depth of prints = Weight distribution.
How do scientists estimate dinosaur speed from trackways?
By measuring stride length and foot size, then using modern animal comparisons.
What does a lack of tail drag marks indicate?
That most dinosaurs held their tails off the ground.
