Short Crystal: Quartz and the Fossilized Bird

March 12, 2021 by MichaelG

A recent study in Frontiers in Earth Science reveals that researchers discovered quartz crystals in the stomach of a bird that lived alongside the dinosaurs. The bird, a member of the Enantiornithes clade of fossil birds, appeared to be a sensational discovery, as previously there had never been a find which preserved any traces of food in the fossils stomach which would clue researchers in to the diet of the animal. Many modern birds have what’s called a gizzard, a thick and muscular portion of the stomach used to help digest food. Often birds swallow small stones know as gizzard stones, which make their way to the gizzard itself where it helps to crush tough or difficult to digest food. These stones are know as gastroliths and have been found in some dino and bird fossils providing hints as to the diet of those animals. The presense of stones in the stomach, though isn’t defiinitive as to the purpose of the stones. There are some modern birtds of prey that swallow rocks to help move material through their digestive tract, cleaning it out, and it’s hard to differentiate between a gastrolith and a gastrolith that is a gizzard stone without knowing anything about the diet and habits of the animal using the stone. In the end, the reesearchers determined that the quart material found where the birds stomach would have been probably was a gastrolight at all. After exposing the supposed gastroliths to X-rays and a scanning electron microscope it was determined that the rocks were actually chalcedony crystals, quartz that grew in sedimentary rocks. There is evidence of chalcedony crystals forming with a clamshell, or replacing minerals in fossil bones. Furthermore, the crystals in this case were all connected in a thin sheet rather than separate rocks. The rocks were also much larger than would be expected of rocks swallowed by a bird that size. In the end there just wasn’t enough evidence, and some negative evidence against the idea that the rocks were in the birds stomach. Just goes to show, never count your gastroliths before they’s been swallowed.

We don’t have any examples of Enantiornithes, but you can check our our collection of fossils for sale here.

_{Top image is a photograph of the holotype of Zhouornis hani, a type of Enantiornithes,
By Yuguang Zhang, Jingmai O’Connor, Liu Di, Meng Qingjin, Trond Sigurdsen, Luis M. Chiappe – https://peerj.com/articles/407/, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=33060650}