 Trilobites had a stomach, new fossils show Washington (UPI) Sep 21, 2017 - Trilobites, the first ubiquitous animal in the fossil record, evolved a stomach more than 500 million years ago. The simple organism's digestive tract was revealed in a new survey of fossil specimens recovered from China. The findings -- detailed this week in the journal PLOS ONE -- suggest the first animal stomachs evolved 20 million years earlier than previously thought. Researchers identified stomachs among two early trilobite species. Trilobite exoskeletons were rich in minerals, which is one of the reason why they preserved so well. But even among the most well-preserved fossils, it's rare for soft tissue to survive 500 million years. "It's very rare to see the preservation of soft tissues like organs or appendages in trilobites, and because of this, our knowledge of the trilobite digestive system comes from a small number of specimens," Melanie Hopkins, an assistant curator in the paleontology division at the American Museum of Natural History, said in a news release. "The new material in this study really expands our understanding." Trilobites first emerged in the Early Cambrian period and stuck around for some 300 million years, thriving throughout the lower Paleozoic era. The horseshoe crab-like creatures were wiped out by a mass extinction event at the end of the Permian. During their reign, the marine arthropods evolved 20,000 species. Scientists previously identified an expanded stomach, called a "crop," among later trilobite species. Until now, researchers though early trilobites had only a simple digestive tube -- no crop. But among the 270 specimens recovered from a quarry in China's southern Yunnan Province, researchers found evidence of an expanded stomach -- proof the earliest stomach emerged roughly 514 million years ago. "This is a very rigorous study based on multiple specimens, and it shows that we should start thinking about this aspect of trilobite biology and evolution in a different way," Hopkins said.
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Paleontologists have found evidence that some large plant-eating dinosaurs also liked to snack on crustaceans. The revelation was made possible by 75-million-year-old dino coprolites -- fossilized feces -- discovered in Utah.
"From what we know about dinosaurs, this was a totally unexpected behavior," Karen Chin, curator of paleontology at the University of Colorado's Museum of Natural History, said in a news release. "It was such a surprising discovery we wondered what the motivation could have been."
Researchers found decaying, coniferous wood inside the fossilized dino dung. And a closer look revealed fragments of fossilized shells. Paleontologists found crustacean remains in 10 coprolite samples spread across 13 miles -- proof, they say, that the dinosaurs were targeting crustaceans on purpose.
The fragments were also large enough to suggest the shells were at least two inches long, some more than half as long as the beak of a common hadrosaur -- suggesting the dinosaurs didn't accidentally swallow a shell.
Hadrosuars' beak-like bills and thousands of grinding teeth evolved to clip and break down sinuous plant fibers, but they could have easily doubled as shell crushers.
"While it is difficult to prove intent regarding feeding strategies, I suspect these dinosaurs targeted rotting wood because it was a great source of protein in the form of insects, crustaceans and other invertebrates," said Chin. "If we take into account the size of the crustaceans and that they were probably wriggling when they were scooped up, the dinosaurs would have likely been aware of them and made a choice to ingest them."
Chin and her colleagues detailed their logic in a new paper, published this week in the journal Scientific Reports.
Chin suggests the feeding behavior may have be seasonal, or even tied to breeding or egg-laying. Contemporary bird species, distant relatives of dinosaurs, often up their protein and calcium consumption during breeding season. Additional analysis of the coprolites revealed significant amounts of the calcium.
Most hadrosaurs grew to roughly 30 feet in length and were marked by crests on the top of their heads. Paleontologists believe the bipedal dinosaurs traveled in herds of a few dozen, and nurtured their young in a communal environment.
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Dinosaur evolution: Lumbering giants had agile ancestors
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