Episode 32 – The Changing Face of Crocodiles

Past Time
Past Time
Episode 32 - The Changing Face of Crocodiles

Episode 32 – The Changing Face of Crocodiles


Every living thing grows up, and this episode of “Past Time” explores the evolution of the growing process. Specifically, we explore the evolution of growth in crocodiles, and how changes to the growing process at the earliest stages of crocodile development help produce the wide array of crocodile snout shapes we see today and in the fossil record. Increase the rate of snout growth in an embryonic croc, and you can produce an adult with a narrow, tubular snout like an Indian gharial or an African slender-snouted crocodile. Slow that process down, and you can produce an adult with a short, rounded snout like a broad-snouted caiman or an African dwarf crocodile.


Paleontologist/Developmental biologist Zachary Morris spritzes water over an incubator filled with Alligator eggs.

Our guest this week is Zachary Morris, a Ph.D. student at Harvard University who studies growth in crocodylians. He wields both the fossil record and the skeletons of modern crocodylians—from tiny embryos to giant adults—to study that very topic. To examine the shape changes in the skull of crocodylians through the growth process, Zach has traveled the world to collect eggs, embryos, juveniles, and adults to build 3D models of skull anatomy. He delved into the collections of museums around the world to find nests and eggs of rare crocodiles that were collected by explorers hundreds of years ago. Zoos were also a critical resource for eggs of breeding species.


Further reading and links –

  • The original paper by Zach and his research team was published in the journal Proceedings of the Royal Society B in Spring 2019.
  • To learn more about Zach and his research, visit his research site.
  • To see all the snout shapes that exist in modern crocodylians and their fossil cousins, check out this amazing review by crocodylian expert Dr. Christopher Brochu.
  • If you’re interested in visiting ALL the crocodylian species in the world, travel to Florida for a visit to the St. Augustine Alligator Farm. It’s not so much a farm as a glorious reptile zoo with a deep dedication to the research and conservation of endangered reptile species.
  • For more information on reproduction in modern crocodylians—from mating rituals to nesting to parenting strategies—the IUCN Crocodylian Specialist Group produced this amazing summary.

Media Credits –


Filed under: Biology, Paleontology, alligator, biologist, bird, caiman, chicken, crocodile, crocodylia, development, dinosaur, embryo, fossil, paleontologist, skeleton, skull

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