Why Did T. Rex Have Tiny Arms? | Tumble Episode
Why did T. Rex have such tiny arms? In this episode you'll meet paleontologist Elizabeth Steell, who's stepped into a decades-old dinosaur debate with a stunning new theory involving giant heads, evolutionary trade-offs, and some serious math. Will it convince you? Listen and find out!
🎧 Listen to the Episode
🦖What Kids Will Learn
Why T. Rex had such tiny arms — and how evolution can trade off one body part to build up another.
How scientists use math to test theories about how extinct animals lived, by comparing measurements like skull strength, arm length, and body size across species.
How scientists use evidence to decide the merits of different theories.
🔎About The Featured Expert
Elizabeth Steell, Ph.D. is the Sarah Woodhead Research Fellow in Earth Sciences at Girton College, University of Cambridge, whose research focuses on the skeletal evolution and fossil record of birds — work that helps scientists understand the deeper story of how dinosaurs evolved into the birds we know today. She earned an MSci from University College London and a Ph.D. from the University of Cambridge, later returning to UCL as a teaching lecturer in palaeobiology before joining Girton as a fellow. Outside the lab, Elizabeth is an avid birdwatcher — she served as President of the Cambridge University Ornithology Society and started a weekly bird walk that's still running today.
🧑‍🏫 Classroom & Home Resources
đź”— NGSS Alignment:Â 3-LS4-1, 3-LS4-2
đź“śScience and Engineering Practices: Analyzing and Interpreting Data, Engaging in Argument from Evidence
đź“š Learn More:
Read the full Cambridge University press release on the study, including quotes from Elizabeth and her co-authors
Learn about other dinosaurs with unusual arms on list from the Field Museum.
đź’¬ Discussion Questions
Were you convinced by the "big head" theory presented in this episode? Why or why not?
Can you think of any other reasons why a dinosaur might have short arms that weren't mentioned in the episode?
What do you think Lizzy's story of investigating a theory about dinosaurs tells you about science?
🎧 More Episodes About Dinosaurs: The Dino Butt Fossil, How Were Dinosaur Tracks Made?, Was T. Rex Smart?
📚 For Teachers: Explore our Audio Courses for NGSS-aligned science learning.
✉️ Don’t miss new episodes! Subscribe wherever you get your podcasts!
🫶Support Tumble!
Click here to become a Patron! Ad-free early access to episodes is just $1/month, and for just $5/month, get a birthday shout out on our feed!
Click here to visit the Tumble Merch Store! T-shirts and other merch (including merch specific to this episode) are available for purchase.
