Although they perhaps were not allowed to say it plainly in their published study, three scientists have identified a clear case of exchanging shit for brains. Details (with some euphemisms) are in the study:
“Coprolites From Calvert Cliffs: Miocene Fecal Pellets and Burrowed Crocodilian Droppings from the Chesapeake Group of Maryland, U.S.A.“, Stephen J. Godfrey, Alberto Collareta, and John R. Nance, Rivista Italiana di Paleontologia e Stratigrafia [Research in Paleontology and Stratigraphy], vol. 128, no. 1, March 2022, pp. 69-79. The authors, at the Smithsonian Institution, the Università di Pisa, and the Calvert Marine Museum, report:
New finds of remarkable coprolites (fossilized feces) are here reported from the famous Miocene marine sediments of the Chesapeake Group exposed along Calvert Cliffs (Maryland, U.S.A.)….
[H]ere we provide the first description of tiny invertebrate fecal pellets. Thus far, these fecal pellets have only been found in the upper Miocene (Tortonian) St. Marys Formation. The micro-coprolites represent the coprulid ichnospecies Coprulus oblongus. The fecal pellets are found in small clusters or strings of dozens to masses of many hundreds….
[Specimen] CMM-V-2022 (Fig. 3B-D, the fecal pellet-infilled neurocranium of [the specimen] Astroscopus countermani ) is the first fossilized vertebrate braincase known to be infilled with feces…
In the News, Ever So Slightly Clad
News editors also, so far, have used slightly twisty language to tell the tale. The New York Times, for example, gives this headline and subheadline to an account written by Jeanne Timmons: “Why Did a Fish Have Fossilized Feces Where Its Brain Once Was? It’s the first time a vertebrate’s braincase has ever been found full of coprolites, scientists say.”