The common name is “gizzard stone” and they are definitely a real “thing”. Birds (today’s descendants of dinosaurs) still have them. In brief, a gastrolith is a rock held inside a gastrointestinal tract.
Just like today’s birds, scientists believe that dinosaurs swallowed their food whole and let the gizzard stones break down the plant fibers. For example, Tempskya Ferns (now extinct along with the dinosaurs) were able to grow to heights of fifty feet because the “stem” of the fern was encased in tough fibers to hold it upright. Try digesting a piece of rope. Taint easy, McGee.
In spite of all the reasons supporting the real existence of gastroliths as a kind of dinosaur “fossil”, they’re surrounded by controversy. Why? Because a “gut-polished” dinosaur gastrolith is almost completely indistinguishable from a stream or ocean polished beach agate. When confronted with a rock that a rockhound claims is a real gastrolith, paleontologists, aware of the long history of fakes and mis-identification of fossils, will say, “Show me the evidence.”
This is especially true because there’s very little to be gained. From the point of view of the paleontologist, you're highly unlikely to get published in a prestigious scientific journal – and nail down tenure for your professorship at a university – with an article about gastroliths. But if you lend credibility to a rockhound claim, you probably will endure the ”the slings and arrows” of rival paleontologists who will point out that there is really no proof.
Gastroliths from Jurassic strata near Starr Springs, Utah. – Wikipedia
Wikipedia has an excellent article about gastroliths. This article has recently been revised at Wikipedia. The tone of the article used to be that it was almost impossible to determine whether a rock is a gastrolith or a common beach rock. The previous version included three conditions that a common homespun rockhound must satisfy before a reputable paleontologist will cease being supercilious concerning the claim.
It should be rounded on all edges (and some are polished) because inside a dinosaur's gizzard any genuine gastrolith would have been acted upon by other stones and fibrous materials in a process similar to the action of a rock tumbler.
The stone must be unlike the rock found in its geological vicinity, i.e., its geologic context.
The stone must be found with the fossils of the dinosaur which ingested it.
Wikipedia notes that the last condition is the one that crushes rockhound claims. Few rockhounds keep authenticated field notes when they pick up a rock. I know my dad never did.
Wikipedia cites Oliver Wings, Director at the Natural History Museum in Bamberg, Bavaria, as a paleontologist whose eyebrows are permanently raised concerning gastroliths. But all that has changed in Wikipedia now. Today, Wikipedia makes this statement:
"Gastroliths can be distinguished from stream- or beach-rounded rocks by several criteria: gastroliths are highly polished on the higher surfaces, with little or no polish in depressions or crevices, often strongly resembling the surface of worn animal teeth. Stream- or beach-worn rocks, particularly in a high-impact environment, show less polishing on higher surfaces, often with many small pits or cracks on these higher surfaces. Finally, highly polished gastroliths often show long microscopic rilles, presumably caused by contact with stomach acid."
William Stokes, a paleontologist at Brigham Young University in Utah, was a rare authority who was willing to stick his neck out and back up a few claims … if there were authenticated field notes by a certified paleontologist.
Nonetheless, my dad picked up a lotta dino bone as a rockhound. Some of it is still on display at prehistoric museums. One of his favorite rockhound haunts was Starr Springs (On the flanks of the Henry Mountains!) The gastroliths my dad brought back were definitely found with the fossils of dinosaur bones. … But you only have my word for it. With my testimony, and five bucks, you can still buy a cup of coffee.
My Dad's Gastroliths
Even though my dad’s gastroliths will only get you arguments as a dinosaur fossil, a lot of them are really beautiful rocks. It would be a shame to cut them, although you could make great cabs from some of them. Another great thing about them is that these were agate well before most dino bone and petrified wood was even buried to start the process of becoming a fossil. Otherwise, they wouldn’t have been around for the dinosaur to swallow. The geological formations that these agates were born in have probably been washed down the Colorado River for many millions of years before the dinosaurs.
If you’re interested in scoring a genuine dinosaur gizzard stone, send me a message at KinesavaROCKS.com. It can be arranged!
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