Paleontologist: The giant pterosaur Quetzalcoatlus had an eleven-meter wingspan and was too heavy to take off merely by flapping its wings, even with a running start. One biomechanics researcher found that Quetzalcoatlus had wings that were far sturdier than it would have needed during flight, and concluded that it took off by using the wings as forelimbs, beginning its flight by leaping with all four “legs.” However, this hypothesis is implausible, since Quetzalcoatlus had to attain a speed of at least forty-eight kilometers per hour to take off, which would have been impossible from a standing jump.
Of the following, which, if true, would be the most effective rebuttal the biomechanics researcher could make to the paleontologist’s argument?
- A. Quetzalcoatlus could plausibly have taken off by diving off a cliff from its hind limbs, then using the fall to accelerate.
- B. Most other pterosaur species are known to have taken off by flapping their wings after a running start.
- C. The sturdy forelimbs of Quetzalcoatlus could have helped it to subdue its prey when not in flight.
- D. Quetzalcoatlus could plausibly have run fast enough to take off by leaping into the air after a running start.
- E. Researchers know of no plausible way in which any giant pterosaur species could have attained a speed of 48 kilometers per hour before taking off.
Solution:
Passage Analysis:
| Text from Passage | Analysis |
| The giant pterosaur Quetzalcoatlus had an eleven-meter wingspan and was too heavy to take off merely by flapping its wings, even with a running start. | What it says: This huge prehistoric flying creature couldn’t get airborne just by flapping – it was too heavy even with a running start What it does: Sets up the basic problem that needs solving – how did this thing actually fly? What it is: Paleontologist’s background information Visualization: Wingspan = 11 meters (about 36 feet, roughly 2.5 car lengths), Weight = too heavy for normal takeoff |
| One biomechanics researcher found that Quetzalcoatlus had wings that were far sturdier than it would have needed during flight, and concluded that it took off by using the wings as forelimbs, beginning its flight by leaping with all four “legs.” | What it says: A researcher noticed the wings were way stronger than needed for flying and thinks it used them like front legs to jump into flight What it does: Introduces a proposed solution to the takeoff problem from the first statement What it is: Research finding and hypothesis Visualization: Normal wing strength needed = 100%, Actual wing strength = 150-200%, Method = 4-legged jump takeoff |
| However, this hypothesis is implausible, since Quetzalcoatlus had to attain a speed of at least forty-eight kilometers per hour to take off, which would have been impossible from a standing jump. | What it says: The paleontologist thinks this jumping idea won’t work because the creature needed to reach 48 km/h to take off, which is impossible from a standing jump What it does: Directly attacks the researcher’s hypothesis by showing a fatal flaw in the speed requirements What it is: Paleontologist’s counterargument Visualization: Required takeoff speed = 48 km/h (about 30 mph), Standing jump speed = much less than 48 km/h |
Argument Flow:
The paleontologist starts by establishing that Quetzalcoatlus had a takeoff problem, then presents a researcher’s proposed solution (four-legged jumping), and finally attacks that solution by showing it couldn’t generate enough speed.
Main Conclusion:
The biomechanics researcher’s hypothesis that Quetzalcoatlus took off by jumping with all four limbs is implausible.
Logical Structure:
The paleontologist uses a speed requirement (48 km/h needed for takeoff) to show that the proposed jumping method is physically impossible, thereby rejecting the researcher’s solution to the original flight problem.
Prethinking:
Question type:
Weaken – We need to find information that would reduce belief in the paleontologist’s argument that the four-legged jumping hypothesis is implausible
Precision of Claims
The paleontologist’s argument hinges on a specific speed requirement (48 km/h minimum takeoff speed) and claims this speed is impossible to achieve from a standing jump using four limbs
Strategy
To weaken the paleontologist’s argument, we need to attack either: (1) the assumption that a four-legged jump would be from a standing position, (2) the assumption that 48 km/h is impossible to achieve with the proposed method, or (3) show that the speed requirement calculation might be flawed for this specific takeoff method
Answer Choices Explained
A. Quetzalcoatlus could plausibly have taken off by diving off a cliff from its hind limbs, then using the fall to accelerate.
This suggests an entirely different takeoff method (cliff diving) rather than defending the original four-legged jumping hypothesis. While this might solve the speed problem, it doesn’t actually rebut the paleontologist’s criticism of the researcher’s specific theory about using wings as forelimbs for jumping takeoff.
B. Most other pterosaur species are known to have taken off by flapping their wings after a running start.
This talks about what most other pterosaur species did, but we’re specifically discussing Quetzalcoatlus, which the passage already established was too heavy to take off by normal wing-flapping methods. Information about other species doesn’t address the speed criticism of the four-legged jumping hypothesis.
C. The sturdy forelimbs of Quetzalcoatlus could have helped it to subdue its prey when not in flight.
This provides an alternative explanation for why Quetzalcoatlus had sturdy wings (prey subduing), but it doesn’t defend the takeoff hypothesis at all. It actually undermines the researcher’s theory by suggesting the sturdy wings served a different purpose entirely, rather than rebutting the speed objection.
D. Quetzalcoatlus could plausibly have run fast enough to take off by leaping into the air after a running start.
This directly counters the paleontologist’s speed objection. The paleontologist claimed 48 km/h was ‘impossible from a standing jump,’ but this choice clarifies that the four-legged jumping could happen after a running start, not from a standing position. This removes the speed limitation that formed the basis of the paleontologist’s criticism, effectively defending the researcher’s hypothesis.
E. Researchers know of no plausible way in which any giant pterosaur species could have attained a speed of 48 kilometers per hour before taking off.
This actually strengthens the paleontologist’s argument rather than providing a rebuttal. If no giant pterosaur could reach 48 km/h before takeoff, this supports the claim that the four-legged jumping method wouldn’t work, making the researcher’s hypothesis even less plausible.
