Monday, September 7, 2015

Dinosaur gastroliths

Gastroliths are literally “stomach stones.” It has long been postulated that they were swallowed voluntarily by giant sauropods (herbivorous dinosaurs) for the purpose of aiding digestion by grinding food material. 

Gastroliths look just like highly polished river gravel, and this fact has helped convince some paleontologists that gastroliths are nothing more than sedimentary gravel and never used by dinosaurs to aid their digestion process. It would follow, therefore, that if you believe you have found "stomach stones," it would strengthen your hypothesis if you could show that they came from inside of a dinosaur skeleton in the stomach area.

Many years ago, a reputable vertebrate paleontologist gave me a stomach stone (see the red stone shown below), which he said that he had collected from the stomach area of a large sauropod of Late Jurassic age in the San Rafael Swell area of Utah.

A gastrolith 9 cm long (= a small cobble) from Utah. The rock, which is heavy, is an iron-bearing (reddish) quartzite.

The other picture (shown below) is of two other gastroliths, also from Utah. These specimens were part of a private collection that was sold.

Two gastroliths (small one is 1.8 cm long = large pebble; large one is 3.8 cm long = very large pebble) from Utah. The rock type, which is lightweight, is a hard but highly polished detrital sedimentary rock (probably coarse-grained sandstone).

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