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As Jedi Master Qui-Gon Jinn said, “There is always a bigger fish.” Or in the case of the Triassic Period, there is always a larger aquatic reptile, as this incredible fossil demonstrates.
New research published in iScience offers the oldest direct evidence of “mega-predation” in the fossil record, in which a top predator feeds on preys of formidable size.
The fossil, found in a quarry in southwest China’s Guizhou Province, appears to show a 15-foot-long (5-meter) ichthyosaur (pronounced “ick-thee-oh-sore”) shortly after feasting on a 12 foot long thalattosaurus (4 meters). Unfortunately, the ichthyosaur probably died soon after its meal, having bit more than it could handle.
Ichthyosaurs were dolphin-like aquatic reptiles that emerged during the Triassic. This particular specimen belonged to a species of ichthyosaur known as the Guizhouichthyosaurus tangae, which reached a length of 10 meters. Its presumed prey, a species of thalattosaurus called Xinpusaurus xingyiensis, looked more like a lizard, with four limbs that he used to paddle in water. The new fossil is the first direct evidence to suggest that at least some species of ichthyosaurs were top predators, similar to orcas today.
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The nearly complete fossil, dated 240 million years ago, suggests the ichthyosaur swallowed an animal not much smaller than itself, which turned out to be a fatal decision. Prior to this discovery, scientists had “never found articulated remains of a large reptile in the stomachs of gigantic predators from the dinosaur age, such as marine reptiles and dinosaurs,” said Ryosuke Motani, co -author of the study and paleontologist. from the University of California, Davis, in a UCD press release. Before this discovery, scientists believed ichthyosaurs to feed exclusively on fish and cephalopods.
“Finding an animal other than fish or squid in the contents of an ichthyosaur’s stomach is incredibly rare – and in fact, finding fish or squid in an ichthyosaur’s stomach is also quite rare,” Dean Lomax, paleontologist at the University of Manchester who was not. involved in the new research, said in an e-mail. “Only a handful of other different types of animals have been found in the stomach of an ichthyosaur for food, so the finding of a fairly large ichthyosaur with a relatively large thalattosaurus dinner is very unusual.
Lomax knows a thing or two about the fossils embedded within the fossils. In 2018, he co-wrote a research article describing a pregnant ichthyosaur fossil with several unborn young still crammed into its ribs.
“One of the most important things about specimens like this is that they provide absolutely unique and straightforward information about the behavior of long-extinct species,” Lomax said. “It’s easy to assume that X fed off Y, but when you have evidence like this, there is no more guesswork.”
It is not known whether the new fossil is an example of predation or recovery, the authors admit. Cleanup does not seem likely, however, given the evidence; limbs tend to fall off decaying bodies before the tail falls. In this specimen, we see the opposite: the members of the thalattosaurus are still attached to its body, but the tail is missing. Surprisingly, paleontologists found the fossilized dismembered tail of this creature a few feet away, which could have been lost during its fateful encounter with the ichthyosaur, according to the authors. Regardless, new evidence suggests that this species of ichthyosaur, whether hunter or scavenger, consumed large meals, which was not previously known.
The fact that the tail was found nearby seemed almost too good to be true, so we asked Lomax what he thought about it.
“Your remark on the tail also sparked my curiosity, although it seems genuine,” he says. “It caught my interest, however, as the authors point out that the ‘predator probably died soon after ingesting the prey.’ They are alluding to this by assuming that an isolated tail of a thalattosaurus was from the same individual consumed by the ichthyosaur. If correct, it could suggest that the predator bit more than it could chew, in that it was a much larger meal than he had expected and which could have led at its fall.
It’s unclear exactly why the ichthyosaur died, but assuming this interpretation is correct – that the isolated tail belongs to the same thalattosaurus – then the ichthyosaur’s death could be linked to its heavy meal, Lomax explained.
Another possibility is that the two sea creatures died on top of each other and the fossils are simply juxtaposed. And indeed, the thalattosaurus fossil shows no sign of being degraded by stomach acid, but, to be honest, this observation also makes sense when you consider the preferred hypothesis: that the ichthyosaur is died shortly after swallowing the thalattosaurus.
The discovery sheds new light on the eating habits of ichthyosaurs, which were believed to feast entirely on cephalopods due to their tiny, ankle-shaped teeth. New evidence suggests the opposite – that these teeth were used to grab prey, smash thorns, and tear flesh.
“Now we can seriously consider that they ate large animals, even when they had clenched teeth,” Motani explained in a Cell Press press release. “It’s been suggested before that maybe a tip wasn’t crucial, and our discovery really supports it. It’s pretty clear that this animal could process this big food using dull teeth.
Modern predators such as orcas and leopard seals apply similar predatory tactics, in what is a possible example of convergent evolution. And indeed, the ichthyosaur itself is the poster child for a convergent evolution, where unrelated species develop similar physical characteristics. Ichthyosaurs are generally compared to dolphins, but as new research shows, a more accurate comparison might be with killer whales.
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