A couple of last (or near-to-last) meals from the dim past have lately demonstrated the remarkable stories we can turn up when poking around inside prehistoric bellies.

A study published on August 20 in iScience delved into the petrified innards of a roughly 5-metre-long (16-foot) ichthyosaur fossil from the Triassic discovered in southwestern China. Within this Guizhouichthyosaurus specimen, the researchers say they found what likely represents the earliest yet-discovered evidence of "megapredation": when a large predator preys on another large – human-sized or bigger, roughly speaking – animal.

This graphic shows the fossil and compares the size of the two marine reptiles. Image © Da-Yong Jiang, et al.

In shallow seas some 240 million years ago, Guizhouichthyosaurus appears to have dismembered and consumed the trunk of another marine reptile, the thalattosaur Xinpusaurus xingyiensis, estimated at a highly respectable 4 metres (13 feet). This, according to the study’s authors, "sets the record for the largest prey size of Mesozoic marine reptiles" yet documented.

Some 23 metres (75 feet) away from the well-fed ichthyosaur, an intact segment of thalattosaur tail was found – quite possibly, the researchers point out, part of the same unfortunate prey animal.

Sporting big but blunt teeth, Guizhouichthyosaurus – which roughly straddled the size spectrum of modern-day great white sharks and orcas – has often been conceived of as a hunter of fairly small, soft-bodied quarry. "Its teeth look like they are good for grasping squids," lead author Da-Yong Jiang, a paleontologist at Peking University, told Reuters. "So it was a surprise to find such large prey."

A closeup of the the ichthyosaur's teeth. Image © Da-Yong Jiang, et al.

With evidence suggesting predation and not a scavenging event, the researchers proposed the ichthyosaur may have killed the thalattosaur in a "grip-and-tear" style of attack similar to that employed by such large aquatic predators as orcas, leopard seals, and crocodilians.

Speaking to Reuters, another of the study’s authors, University of California-Davis paleobiologist Ryosuke Motani, sketched out what the undersea drama might have looked like. "The prey is lighter than the predator but its resistance must have been fierce," he said. "The predator probably damaged its neck to some extent while subduing the prey. Then it took the head and tail of the prey off through jerking and twisting, and swallowed the trunk using inertia and gravity."

The minimal digestive breakdown seen on the thalattosaur segment inside the ichthyosaur indicates the predator itself kicked the bucket shortly after its feed – perhaps, as Motani suggested, having suffered serious injury taking out the Xinpusaurus.

Ichthyosaurs – big-eyed, streamlined beasts that kind of looked like a shark/dolphin/swordfish mashup – emerged in the Early Triassic and continued plying those reptile-ridden Mesozoic seas into the Late Cretaceous. The lizard-esque thalattosaurs, by contrast, had a shorter career confined (so far as we know) to the Triassic.

Fast-forward in time to another, still-ancient G.I. tract: that of a 14,000-year-old puppy, to be specific. Its mummified carcass – recovered in 2011 from the Siberian permafrost around Tumat, Yakutia – contained in its stomach a hairy mass originally speculated to derive from a cave lion. However, results of testing by the Swedish Museum of Natural History, announced this month, pegged the swallowed material as woolly rhinoceros:

The revelation comes with the release of an August 13 paper in Current Biology that used genetic analysis to investigate the extinction of the woolly rhino. The rhino tissue recovered from the Pleistocene puppy – among the samples tapped in the study for DNA sequencing – was dated to approximately 14,400 years old, about the time when this horned and hirsute "megaherbivore" shuffled off the tree of life. (The paper suggests that a fast-warming climate, and not human hunting, was likely the main factor in the woolly rhino’s ultimate doom.)

"As far as we know, it is very unusual to find tissue from another animal preserved in the stomach, although some studies have been done on plant remains from stomach contents," Edana Lord, one of the study’s authors and a Ph.D. student at Stockholm’s Centre for Palaeogenetics, told Inverse.

Another of the authors, Love Dalén, echoed the point to CNN. "It’s completely unheard of," he said. "I’m not aware of any frozen Ice Age carnivore where they have found pieces of tissue inside."

It’s not clear by what means the Tumat puppy came to gnaw on a hulking rhino: perhaps sharing in the spoils of its pack’s kill, or scavenging one made by another carnivore or humans. (Whether the puppy is a dog or a wolf also isn’t settled: "I think it falls around that critical point for the dog/wolf domestication," Lord told Live Science.) Either way – as with the thalattosaur-gulping ichthyosaur – the young canid didn’t appear to live long after its meal, as the rhino tissue isn’t much digested.