Helicoprion: 114 Years of Getting the Buzzsaw Shark Wrong

In 1899 a Russian geologist described a fossil he could not explain: a flat spiral of more than a hundred serrated teeth, each larger than the last. He was certain it came from an animal. He could not work out where on the animal it went. That question stayed open for 114 years — not for lack of effort, but because Helicoprion was a cartilaginous fish, and cartilage does not fossilise. For over a century, everything anyone had was the spiral itself. One organ, and nothing to hang it on. In 2013 a team at Idaho State University put one particular slab into a CT scanner and got the answer. The spiral was not a saw carried in the open. It filled the entire lower jaw, braced in cartilage, with only the working blades exposed at the back of the mouth. And the same scan showed something else: this animal was not a shark. It was an early relative of the chimaeras — the quiet deep-water ratfish that still, today, grow tooth plates they will never shed. This film is built on the peer-reviewed record: Tapanila et al. (Biology Letters, Royal Society, 2013), Ramsay et al. (Journal of Morphology, 2015), Tapanila & Pruitt (Journal of Paleontology, 2013), and Tapanila et al. (The Anatomical Record, 2020). Where the popular figures and the published figures disagree — particularly on body size — the film says so and uses the published ones. It also corrects one of the most widely repeated claims about this animal: Helicoprion did not survive the end-Permian extinction. There are no valid Triassic records. All archive imagery is used under free licences. Attributions below. Chapters 0:00 A spiral nobody could place 1:14 Krasnoufimsk, 1899 2:55 The man who mapped a continent 5:51 Why cartilage leaves nothing 7:19 A gallery of wrong animals 10:24 Why the spirals come out of Idaho 12:48 Idaho 4, in a drawer since 1950 14:28 The scanner 16:18 The spiral was the jaw 18:26 The upper jaw was empty 19:20 One blade, one anvil 21:07 Soft bodies, and the wear that isn't there 22:44 Every tooth it ever grew 24:39 It was not a shark 26:34 What a ratfish is 28:43 The saw-jawed family 30:31 How big, honestly 32:30 One coastline, one ocean 34:13 It vanished without an event 36:00 Idaho No. 5 comes home 37:57 A record kept in order Credits Archive images (69) are public domain or CC0, via Wikimedia Commons. Images used under Creative Commons Attribution (69), via Wikimedia Commons: · James St. John (47 images) — CC BY 2.0 · unknown author (5 images) — CC BY 4.0 · Dmitry Bogdanov (2 images) — CC BY 3.0 · Viktor V. Grøtan (2 images) — CC BY 4.0 · Gasmasque — CC BY 4.0 · L. Manuelli, G. Clément, M. Herbin, B. Fritzch, P. E. Ahlberg, K. Dollman & L. Cavin — CC BY 4.0 · Leif Tapanila ,Jesse Pruitt — CC BY 4.0 · Mark J. MacDougall, Aaron R. H. LeBlanc, Robert R. Reisz — CC BY 2.5 · Massimo Bernardi, MUSE, Trento, Italy. Published by Michael J. Benton. — CC BY 4.0 · MostlyDross from Springfield, VA, USA — CC BY 2.0 · Some-media — CC BY 4.0 · Stephan N.F. Spiekman​, James M. Neenan, Nicholas C. Fraser, Vincent Fernandez, Olivier Rieppel, Stefania Nosotti, Torst — CC BY 4.0 · Steve Jurvetson — CC BY 4.0 · User:Captmondo — CC BY 2.5 · prilfish — CC BY 2.0 · wild_wind — CC BY 4.0 · Иван Берестов — CC BY 3.0