I don’t know how I missed this yesterday. National Geographic has an article on an interesting fossil, dating to about 290 MYA (basically, the beginning of the Permian) , that provides some interesting information on food chains.
The fossilized amphibian is also in exactly the right position to suggest it had been eaten–it was lying tail-first along the shark’s digestive tract, according to Kriwet.
“Also, the fish remains are fully enclosed within the amphibian’s outer covering of scales,” he added. That confirms that it was indeed eaten by the amphibian and not the shark.
Before the shark ate it, the amphibian had caught a young fish known as an acanthodian, which was covered in bony spines.
“The fish was swallowed side on, otherwise the spines could have got stuck in the amphibian’s mouth or throat,” Kriwet said.
“The fish is situated in quite the correct area of digestive tract of the amphibian,” said said study co-author Ulriche Heidtke, a paleontologist from the National History Museum of the Palatinate in Bad Dürkheim, Germany.
“It clearly shows the hallmarks of digestion, [such as] disintegration,” he added.
If the shark had eaten the fish first and then the amphibian, they would be placed one after the other in the shark’s stomach, he explained.
National Geographic has the only picture I have been able to find. The find is being published in Proceedings of the Royal Society B and the abstract to the paper can be found here (P.S. if some with access can send me a copy I would appreciate it).