Directions: After reading “Robot re-creates a tetrapod’s moves,” students can apply their knowledge of experimental design to answer the discussion questions provided. The questions encourage students to put themselves in the shoes of scientists studying ancient locomotion. Scientific investigations of ancient locomotion cover concepts in biology, physics, robotics and computer science.

Suggestion for structuring discussion: Divide the class into four groups and review the four research approaches used to study Orobates pabsti listed below. Assign each group one of the research techniques and provide the groups the discussion prompts one at a time. Allow about three minutes for each group to discuss each prompt. Students should summarize their answers for other groups before moving on to the next prompt.

Research approaches:

A. Re-created an Orobates pabsti skeleton from well-preserved fossils found in Germany.

B. Developed a computer simulation that explored hypothetical motion based on the Orobates pabsti skeleton.

C. Studied how modern-day tetrapods including salamanders, skinks, caimans and iguanas walk.

D. Created a robot to act out potential gaits and match those gaits to fossil trackways.

Research approaches:

1. What background knowledge would you need to complete the specified research approach? What type of prior research experience and/or fieldwork would have been helpful?

A. Skeleton re-creation: Knowledge of anatomy, paleontology and biomechanics would be needed to complete the approach. Prior research experience handling and preserving fossils would be helpful.

B. Computer simulation: Knowledge of computer science, modeling, physics and biomechanics would be needed to complete the approach. Prior experience coding and modeling biological systems would be helpful.

C. Studying modern-day tetrapods: Knowledge of anatomy and evolutionary biology, including phylogeny and adaptation, would be needed to complete the approach. Knowledge of the animals’ environment, ecology, life history and behaviors would also be useful. Prior experience handling such animals or observing them in the wild would be helpful.

D. Robot: Knowledge of engineering, robotics, computer science, physics and experimental design would be needed to complete the approach. Prior experience building animal-inspired robots would be helpful.

2. What type of data would you get from this research approach and what insight might that data offer?

A. Skeleton re-creation: Scanning fossils would yield data about the animal’s size and shape and how bones connect at joints. Analyzing how bones fit into joints and the size and number of joints can offer clues to range of motion, which would constrain possible gaits.

B. Computer simulation: Computer simulations could yield data on power expenditure, balance, stability and the force exerted on the ground with each step (ground reaction force) for different gaits. Simulations allow you to analyze a lot of factors in tandem to see what combinations of characteristics make physical sense.

C. Studying modern-day tetrapods: Observing modern-day tetrapods walking could yield data on the animals’ limb sprawl, body height, balance and the ground reaction force with each step. Observing animals in their natural environment could also reveal how they move in different scenarios: when running away from predators or chasing prey, or when climbing or moving through water. In analyzing this data, you could look for patterns between body size or body mass and movement. With phylogenetic information, you could try to understand how tetrapod gaits evolved over time.

D. Robot: The robot would produce different gaits depending on inputs for balance, energy consumption, frequency, limb placement, spine bending and body height, among other factors. Having the robot act out different gaits might allow you to rule out gaits that don’t match the trackways or might lead to toppling on different types of surfaces.

3. Come up with a possible hypothesis about a tetrapod’s gait that could be tested via the approach. State specifically whether your hypothesis applies to modern or ancient tetrapods. What is a possible result relating to the hypothesis?

A. Skeleton re-creation: A student might hypothesize that the ancient tetrapod’s joints didn’t allow for much rotation of the legs. If that hypothesis is true, the animal’s spine might have had to move from side to side as it walked.   

B. Computer simulation: Students might hypothesize that the most energy-efficient gaits of ancient tetrapods come from a tetrapod that stays close to the ground, or that animals that stay close to the ground can move faster. The simulation might reveal these hypotheses to be true or false, or might show that the validity of the hypothesis depends on other factors such as animal size and force applied to the ground with each step.

C. Studying modern-day tetrapods: Students might hypothesize that the speed of modern-day tetrapods correlates with their style of walking (diagonal walk versus pacing versus trot). By looking for patterns in how modern-day tetrapods walk depending on their body size and form, students might gain clues to how ancient tetrapods walked.

D. Robot: Students might hypothesize that a gait that best matches the ancient O. pabsti trackway wouldn’t include much side-to-side movement. Based on data collected during the investigation, students might find that the gaits lacking side-to-side movement would also help the tetrapod conserve energy.

4. What gaps in knowledge would you still have following the investigation? What additional approach could help you fill in the gaps?

A. Skeleton re-creation: Studying a reconstructed skeleton might give scientists an idea of the range of possible tetrapod movement, but it couldn’t pin down a specific movement among the options. Encourage students to think about other characteristics that aren’t preserved and how those characteristics might affect movement. For example, the amount of muscle, fat or other tissue might influence balance and thus gait. An approach that could help fill that knowledge gap would be to study how the gaits of modern-day tetrapods differ based on body composition.

B. Computer simulation: Simulations can give scientists a better idea of how the ancient tetrapod would have walked, but simulations often rely on scientists’ assumptions. For instance, many locomotor simulations assume that the most likely gaits have the lowest energetic cost over a given distance. But that singular goal can lead to extremely unrealistic gaits. Gaps that might improve a simulation include data about the animal’s physiology, including metabolism and energy requirements.

C. Studying modern-day tetrapods: Modern-day tetrapods helped scientists figure out the possible range of motion for O. pabsti, but scientists would need to know how O. pabsti’s body differed from modern-day tetrapods’ bodies. Differences between the life histories and environments of O. pabsti and modern tetrapods might also affect movement. With computer simulations, scientists could see how different factors may impact gait.

D. Robot: Even if scientists zero in on O. pabsti’s walking style, there are still unanswered questions: How did the walking style evolve? Was it a novel innovation for O. pabsti’s lineage? Conducting a similar investigation with older fossils in O. pabsti’s lineage, if they exist, might provide clues to the evolution of this walking style.

5. Scientists used this research approach to study the locomotion of an extinct species. What other types of research questions in other fields currently benefit or could benefit from the approach your group studied? Look up information, if needed, to give an example.

A. Skeleton re-creation: Scientists can learn much more about an animal than its locomotion from studying re-created skeletons. Researchers can gain clues to size of individuals, variation among individuals and how the body might have developed over time. Reconstructed skeletons might also provide clues to how an animal lived. Fossils themselves also offer info: Where the fossil was found and the rock it is encased in can be useful for pinpointing the fossil’s age. Biologists can use their knowledge about living things to learn more about how fossils are related to each other. And in areas where fossils are relatively abundant, such as the Burgess Shale in Canada, counts of individuals and species offer clues to population sizes and how these creatures were dispersed across the ancient world.

B. Computer simulation: Many other fields of science build computer simulations in an attempt to answer research questions. Some of those fields include physics, biology, astronomy and meteorology. Meteorologists, for example, build computer simulations from climate data and past weather patterns in an attempt to predict future weather.

C. Studying modern-day tetrapods: Studying modern-day animals can be useful for engineers. For instance, studying birds’ high-speed turns may help scientists design drones that can pull tight maneuvers in crowded places. And bioengineers have mimicked mantis shrimp vision to build advanced cameras. Encourage students to think about other examples of bioinspired technology, as well as all the questions biologists can answer by studying animals.

D. Robot: Scientists that study modern-day marine organisms also find animal-inspired robots useful. For instance, deep-sea physiologists have used robots to understand how a snailfish can withstand intense pressure and extremely cold temperatures. Animal-inspired robots can also be put to use accomplishing dangerous tasks. For instance, an inchwormlike robot equipped with octopus-inspired suction cups can scale walls. The bot might someday help conduct surveillance or inspect buildings and bridges. And a tiny insect-inspired bot can fly, swim and launch itself from water. Such a bot could one day be used to perform search-and-rescue operations or sample water quality.