Fossilised faeces reveal that vegetarian dinosaurs had a taste for crabs.
NYT Syndicate Plant-eating dinosaurs usually found plenty to eat,
but occasionally they went looking for a nutritional boost. Fossilised
dinosaur droppings from Utah now reveal that 75 million years ago, some
of the animals were snacking on prehistoric crayfish or crabs. The work
suggests that big herbivorous dinosaurs sometimes munched on
crustaceans, likely to get extra protein and calcium into their bodies
before laying eggs, says Karen Chin, a paleontologist at the University
of Colorado Boulder. She and her colleagues reported the discovery in
Scientific Reports. "It's a very unusual case of an
herbivorous dinosaur supplementing its diet with something else,"
says Paul Barrett, a paleontologist at the Natural History Museum in
London. Direct evidence of dinosaur diets is hard to come by. Some
fossil animals have been found with their gut contents intact, but
fossilised dinosaur dung " the most convincing remains of what a
dinosaur actually ate " is rare."Think of a cow pat "
these things get broken down in the environment very easily," says
Barrett. Most of the fossilised faeces, called coprolites, that
researchers uncover come from meat-eating dinosaurs; these are better
preserved than those of plant-eating dinosaurs thanks to minerals in the
bones of the creatures that carnivores consumed. Chin has long hunted
for coprolites from herbivorous dinosaurs. In 2007, she reported finding
fossilised chunks of rotting wood inside coprolites, between about 80
million and 74 million years old, from the Two Medicine rock formation
in Montana. Plant-eating dinosaurs may have chewed the wood in search of
insects and other organisms scurrying inside rotting logs, she proposed.
Then, in 2013, she found many similar coprolites in the Kaiparowits
Formation of Grand Staircase Escalante National Monument in southern
Utah. Along with rotting wood, they contained puzzling fragments of
thin, convex structures. When Chin examined slices of the structures
under a microscope, they looked very much like the outer covering of a
crustacean's leg or claw. She consulted Rodney Feldmann, a
paleontologist at Kent State University in Ohio, who confirmed that they
probably came from a crayfish or crab. DIETARY SUPPLEMENT At the time
the Kaiparowits rocks formed, about 75 million years ago, the landscape
was a wet, subtropical environment much like today's Texas coast.
Chin thinks that local dinosaurs " probably the duck-billed group
called hadrosaurs " went in search of dietary supplements near the
shoreline."You get so many invertebrates hanging out in rotting
logs," she says."There's bugs to eat, and rotting
detritus " it's a really rich place." The fungi that
helped to break down the logs would also have provided extra protein.
Some modern birds with mostly plant-based diets add insects and other
sources of protein before they lay eggs, she notes."You can't
imagine a 20-foot hadrosaur going after a butterfly," Chin
says."They would go for some place that had a predictable,
concentrated source of food " some place like rotting logs."
The rotting wood probably wasn't a main source of dinosaur food
year-round, says Jordan Mallon, a palaeontologist at the Canadian Museum
of Nature in Ottawa."Hadrosaurs were some of the biggest animals in
their ecosystems, so they probably couldn't have afforded to be too
selective about what they were eating anyway, lest they starve to
death." Mallon thinks the dinosaurs might have accidentally
devoured a crayfish or two while feeding, as opposed to seeking the
crustaceans out on purpose. Either way, he says, the latest
findings"provide an excellent glimpse in the lives of these
animals, 75 million years ago."
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