Sharks wouldn’t be known for their fierce teeth today if it weren’t for their ancient scales. LEARN MORE ************** To learn more about this topic, start your googling with these keywords: Dermal denticles: also called placoid scales, they’re the most primitive form of fish scales that are structurally similar to teeth and are today found only in sharks, rays, and chimaeras. Outside-in theory: The strongest theory for the evolution of teeth, which are thought to have evolved from dermal denticle scales. Ostracoderms: Extinct armored jawless fish that lived in the Paleozoic Era Thelodonts: Extinct jawless fish that had individual scales as opposed to plates of armor Placoderms: Now extinct, they were some of the first jawed fish and lived from the Silurian through the Devonian era. SUPPORT MINUTEEARTH ************************** If you like what we do, you can help us!: - Become our patron: https://patreon.com/MinuteEarth - Share this video with your friends and family - Leave us a comment (we read them!) CREDITS ********* Julián Gustavo Gómez (@thejuliangomez) | Script Writer, Narrator and Director Kate Yoshida | Co-Director Arcadi Garcia i Rius (@garirius) | Illustration, Video Editing and Animation Nathaniel Schroeder | Music MinuteEarth is produced by Neptune Studios LLC https://neptunestudios.info/ OUR STAFF ************ Sarah Berman • Arcadi Garcia i Rius David Goldenberg • Julián Gustavo Gómez Melissa Hayes • Alex Reich • Henry Reich • Peter Reich Ever Salazar • Leonardo Souza • Kate Yoshida OUR LINKS ************ Youtube | null TikTok | https://tiktok.com/@minuteearth Twitter | https://twitter.com/MinuteEarth Instagram | https://instagram.com/minute_earth Facebook | https://facebook.com/Minuteearth Website | https://minuteearth.com/ Apple Podcasts| https://podcasts.apple.com/us/podcast/minuteearth/id649211176 REFERENCES ************** Donoghue, Philip CJ, and Martin Rücklin. "The ins and outs of the evolutionary origin of teeth." Evolution & development 18.1 (2016): 19-30. https://onlinelibrary.wiley.com/doi/pdf/10.1111/ede.12099 Fraser, Gareth J., et al. "The odontode explosion: the origin of tooth‐like structures in vertebrates." Bioessays 32.9 (2010): 808-817. https://authors.library.caltech.edu/20188/3/nihms266189.pdf Huysseune, Ann, Jean‐Yves Sire, and P. Eckhard Witten. "Evolutionary and developmental origins of the vertebrate dentition." Journal of Anatomy 214.4 (2009): 465-476. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2736119/ Pennisi, Elizabeth. "Eating Was Tough For Early Tetrapods." (2013): 390-391. https://science.sciencemag.org/content/339/6118/390.full