Xiphactinus: The Fish That Was Killed By Its Own Dinner

In 1952 George F. Sternberg split a block of Kansas chalk and found a four-metre predatory fish with another fish inside it — a Gillicus nearly two metres long, swallowed head-first and almost complete. Both animals died. One inside the other. They stayed that way for about eighty-five million years. That specimen, FHSM VP-333, is the most famous fossil this animal has, and it is not a freak. A Xiphactinus from Nebraska has the same thing inside it. So does one collected near Denver in 1946 — and in that one the swallowed fish is still partly sticking out behind the gills, which means death came within hours. The pattern repeats because of how the animal was built: those fangs grabbed and held, they could not cut, so everything it ate went down whole, and on at least three recorded occasions that is what killed it. The size usually quoted — five to six metres — needs trimming. The largest fully articulated specimen, from Gove County in 1996, is five point two metres. The 1901 American Museum skeleton is four point eight. The fish-in-a-fish is about four. George Sternberg reported individuals up to five point one metres but noted they were incomplete, and the composite his father assembled in 1922 comes in just under five. Five metres is the honest ceiling. A typical adult was three and a half to four and a half. This year the animal got a new line in its record. Stephanie Drumheller and colleagues described a Xiphactinus tooth embedded in the neck vertebra of a young Polycotylus — a plesiosaur — from the Mooreville Chalk of Alabama, a specimen that had been sitting in the Field Museum collections until Christopher Brochu noticed it. Bite marks on bone are common; a tooth left in the bone names the attacker. What the press reports left out is the authors' own caveat, which this film quotes in full: a bite to the neck would certainly have been fatal, if the Polycotylus was not already dead. They cannot separate attack from scavenging, and they say so. It was also prey. A Cretoxyrhina found by George Sternberg in 1908 has Xiphactinus bones inside it, and a Xiphactinus skull at Emporia has a piece of shark tooth lodged in the third vertebra behind the head. And it has no living relatives — not loosely, but as a tested and rejected idea. It looks like a bonytongue, and for decades it was filed near them; Patterson and Rosen showed in 1977 that the resemblance is superficial. Ichthyodectiformes are a stem group of the true teleosts. The whole order is gone. What survives is everything else: this fish is a cousin of nearly every bony fish alive today. Built on the published record: Drumheller et al., Journal of Vertebrate Paleontology (2026); Bardack (1965); Patterson & Rosen (1977); Hay (1898) and Stewart (1898) on the priority of Leidy's name over Cope's Portheus; Mantell's 1822 description of the English material, which he later re-filed as an indeterminate reptile; Everhart on the Kansas chalk. Charles Sternberg's 1917 account of a shark fighting a Xiphactinus is a dramatisation built on a real specimen — we use the specimen, not the story. About the pictures: about four fifths of this film is archive imagery under free licences, and a fifth is motion — stock underwater footage and animated reconstructions of an animal that cannot be filmed. One is a diagram. Thumbnail: fossil photograph by James St. John (CC BY 2.0), via Wikimedia Commons. Full credits below. 0:00 A fish inside a fish 1:32 What the animal actually was 3:09 England had it forty-eight years earlier 4:35 A fragment of fin, and a name 5:57 Cope had the whole fish and still lost 7:46 Five metres is the honest ceiling 9:32 It could not bite pieces off 11:03 FHSM VP-333 12:46 One family, eighty-two years 14:14 A tooth in a plesiosaur's neck 16:05 What the paper does not claim 17:59 It was prey as well 19:27 Cousin to nearly every fish alive 21:41 Why Kansas keeps them whole 23:23 The order that ended Additional footage from Pexels (8 clips). Archive images (43) are public domain or CC0, via Wikimedia Commons. Images used under Creative Commons Attribution (54), via Wikimedia Commons: · James St. John (30 images) — CC BY 2.0 · David Wipf (3 images) — CC BY 2.0 · Dmitry Bogdanov (3 images) — CC BY 3.0 · Neil Pezzoni (3 images) — CC BY 4.0 · A Cynical Idealist (2 images) — CC BY 4.0 · Jonathan Chen (2 images) — CC BY 4.0 · Mark P. Witton (2 images) — CC BY 4.0 · Alexander Grebenkov — CC BY 4.0 · Corbin Rainbolt — CC BY 4.0 · and 7 further authors (7 images) — named in full in the pinned comment Full per-image attribution is in the pinned comment. Narration and score were created for this channel. 10 animated sequences are computer-generated reconstructions, not documentary footage; 1 diagram was drawn for this film.