Crystals in the fossil bird’s stomach complicate the mystery of its diet

Rebuilding bohaiornithid Sulcavis, a close relative of Bohaiornisguoi, hunting insects. Credit: © S. Abramowicz, Dinosaur Institute, Natural History Museum of Los Angeles County.

It is difficult to know what prehistoric animal life was like. Even answering seemingly simple questions, like what they ate, can be a challenge. From time to time, paleontologists are fortunate, and pristine fossils preserve the contents of the animal’s stomach and provide other clues.In a new study of Earth science frontierResearchers investigating fossils of birds that lived with dinosaurs were asked more questions than they answered when they found a crystal in the bird’s stomach.

“I think this is a strange form of soft tissue conservation that I’ve never seen before,” said Jinmai O’Connor, deputy curator of fossil reptiles at the Field Museum in Chicago. “Understanding what is in this bird’s stomach helps to understand what it ate and what role it played in its ecosystem.”

“This paper shows that enantiornithes, one of the important fossil bird clades, do not yet have direct gastric traces or evidence,” said the Chinese Academy of Sciences for vertebrate paleontology. Shumin Liu, a student at the Institute of Science and Paleoanthropology and the first dissertation in the dissertation, said. Author. “I was excited, it’s a breakthrough about them.”

The fossil birds that researchers paid attention to Bohaiornis guoi.. “They are part of an early Cretaceous bird lineage about 120 million years ago,” says O’Connor, who worked on a treatise at IVPP, where Liu was a master’s student. “They still have teeth and claws in their hands, but they’re small, about the size of a pigeon, so they’re not particularly scary.” Bohai Ornis was once the most common bird in the world, Enantiornis. It was part of a group called Kind. Thousands of Enantiornis specimens have been found in the Jehol Biota deposits in northeastern China.

Despite the vast number of finely preserved enantiornithes, none of the stomachs contain trace amounts of food that can tell researchers what these birds ate. “Despite having more enantiornithes than any other group, identify the diet and digestive system of all these other bird groups found in the sediments that record the Jehol Biota. It can be rebuilt, “says O’Connor. “For these people, we don’t have preserved evidence of specimens or diets. That’s really strange.” But in the specimens examined in this new treatise, O’Connor and her colleagues have clues. I did. Previous studies have pointed out the presence of small rocks in the stomach.

Crystals in the fossil bird's stomach complicate the mystery of its diet

X-ray image of crystals in the stomach of Bohaiornisguoi. Credits: © Liu et al, IVPP.

Many living birds have an organ called the gizzard — a thick, muscular part of the stomach that helps them digest food. They swallow small rocks called gizzard stones, which go to the gizzards where they help grind tough food. These gizzard stones, called bezoars, have been found in some dinosaur and bird fossils and provide clues as to what those animals ate. These are associated with a diet of tough plant materials and seeds.

However, the rocks in the animal’s stomach are not necessarily a sign that it is using them to grind food. Some modern birds of prey swallow rocks called rangle to help remove substances from the digestive tract and clean them. You may also find rocks accidentally swallowed by a creature near the dinosaur fossil’s stomach cavity, or you may accidentally find a stone near the fossil. “We need to distinguish between bezoars and bezoars used as gizzard stones,” says O’Connor.

There is no clear evidence of bezoars in Enantiornithes birds, but in a 2015 paper, Bohaiornis guoi The stomach contained rocks that were used as rangles (gastroliths ingested by birds of prey to clean the stomach, but not to digest food). O’Connor was skeptical. The picture of the rock did not look correct. Gastroliths are usually made of different types of rock, with slightly different colors and shapes. All of these rocks were similar in composition to each other and to the fossilized bone itself. Also, they did not seem to be perfectly shaped or grouped. It was too round and scattered. “I didn’t know what they were, but I didn’t seem to have them gastroliths,” she says. So she and her colleagues understood what these rocks were and set out to compare them with the bezoars from other fossil birds and dinosaurs.

Researchers extracted a sample of rock in the stomach of Bohai Ornis and examined it with a scanning electron microscope. Next, the rock was exposed to X-rays to determine the wavelength that the rock absorbed. This helped researchers narrow down what these rocks are made of, as each mineral absorbs different wavelengths.

“We found that the rock fragments, called bezoars, were chalcedony crystals,” says O’Connor. “Chalcedony is basically a crystal that grows in sedimentary rocks. There is no evidence of this in Jehor, but fossil records show evidence that chalcedony crystals are formed within the clamshell or that chalcedony replaces them. There are many. The minerals that make up fossil bones. ”In addition, chalcedony was all interconnected to a single thin crystalline sheet rather than the separate rocks swallowed by the bird.

Crystals in the fossil bird's stomach complicate the mystery of its diet

A fossil specimen of Bohai Ornis with crystals in the stomach. Credits: © Liu et al, IVPP.

When chalcedony was used to aid digestion, the amount of chalcedony present was also incorrect. According to scientific literature, rocks consumed by birds as rangle make up about 3% of their body weight. Bohaiornis probably weighed about 300 grams, so the team was looking for a rangle worth up to 9 grams. “I couldn’t extract the entire sample to figure out how much it weighed, but Schmin was really smart and took a chalcedony that weighed 3 grams. It was huge,” says O’Connor. Than the total size of chalcedony pieces in the stomach of Bohai Ornis.

Combined evidence suggests that Bohaiornis did not have gastroliths to help grind food to help clean its stomach after all. Or, at least, this specimen of Bohaiornis does not contain those bezoars.

“We only have this lack of evidence, and paleontologists always say that lack of evidence is not evidence of lack, but whoever comes up with the maxim is what is complete and clear. There were thousands of specimens, and I never imagined they would preserve soft tissue, “says O’Connor. When the early Cretaceous enantiornis used bezoars, it is very strange that none of the thousands of fossils show them.

O’Connor states that none of the Enantiornithes birds from the Rehe Formation show evidence of stomach contents, but some from Spain have freshwater mussels in their stomachs. I am. However, the mystery remains as to what Bohai Ornis ate and why none of the Enantiornithes had anything in his stomach.

“This study is important because this fossil is the only fossil record of the Enantiornithes, including the possibility of bezoars, and even the actual traces of Jehor’s stomach. In addition, this fossil bird Only clades have no traces of the stomach, but most other clades have these traces, “says Liu.

“We’re always trying to find some evidence, but the specimens proposed to fill this gap unfortunately don’t do that,” says O’Connor. “This is part of an old-fashioned game, part of science, and constantly being fixed. I’m happy when we don’t understand things. That means there’s research to do. It’s exciting. ”

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Crystals in the fossil bird’s stomach complicate the mystery of its diet

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