Directions: Have students read the article “Robot re-creates a tetrapod’s moves” and answer the following questions.

1. What is Orobates pabsti and how is the creature related to humans?

O. pabsti is a four-legged species that lived between 280 million and 290 million years ago. O. pabsti is an early amniote, a member of the group that includes all reptiles and mammals (including humans) living today.

2. Why are scientists interested in how O. pabsti walked?

Understanding how early amniotes walked on land can shed light on the evolution and diversification of amniotes more generally. It also provides clues to how different styles of walking evolved over time.

3. Why is the amniotic membrane considered a “key evolutionary innovation”?

This protective membrane surrounds an embryo and allows animals to bypass the tadpole stage of life. That means these animals can survive entirely on land. The ability to survive entirely on land opened new habitats for organisms to colonize and led to new evolutionary opportunities, and pressures.

4. What techniques did scientists combine to try to understand how O. pabsti moved?

The study of O. pabsti relied on a combination of several tactics — re-creating the skeleton, creating digital and robotic simulations and studying modern species.

5. Why were the conclusions about O. pabsti’s gait surprising?

O. pabsti appears to have held its belly off the ground and didn’t have too much side-to-side movements. Scientists were surprised because they expected this walking style to be found only in more modern four-legged creatures.

6. Based on clues from the article, what does it mean for a gait to be efficient?

Having an efficient gait means the animal spent minimal energy to get from place to place. The animal would be balanced without a lot of slipping or sliding, so as not to waste energy on side to side movements or unnecessary steps.

7. What other research questions related to ancient locomotion might benefit from the approach these researchers used?

Other puzzles of ancient locomotion include how the first birds flew and how human ancestors began walking upright.

8. Identify one word in the article that is unfamiliar and define it from context.

Gait: The sequence of movements that get something from one place to another.

Trackways: Prints left in the ground by a creature as it moves from one place to another.

9. Watch the video provided in the online version of the article, “A four-legged robot hints at how ancient tetrapods walked.” What is one piece of information that appears in both the article and video? What information is in the video but not in the article?

In the video, we see OroBOT moving as it was described in the article. The video gives a sense of how fast OroBOT walks, which isn’t explicitly described in the article.