Parasites wormed their way into dino’s gut
Inside the fossilized guts of a 77-million-year-old dinosaur, scientists have spotted a surprise. The dino’s stomach is crisscrossed with thin tunnels. These may be the once-slimy trails of parasitic worms.
Like ticks and fleas, these worms would have been parasites — biological hitchhikers that steal a meal from their host.
These fossil worm tunnels are the first good evidence that gut parasites infected dinosaurs, the scientists say. Paleontologist Justin Tweet and his colleagues described their finding online June 16 in the Journal of Paleontology.
“Maybe they’re right, maybe they’re not,” cautions Anthony Fiorillo. He’s a paleontologist at the Perot Museum of Nature and Science in Dallas, Texas. What looks like worm tracks could be something else entirely, he points out. “But they’re seeing something no one else has seen before, and that’s pretty awesome.”
Animals living today carry parasites and other microscopic life forms in their bodies. Scientists had guessed that dinosaurs did too. “But that doesn’t mean that anybody ever expected to see them,” says Tweet. A former researcher at the University of Colorado Boulder, he now consults for the National Park Service.
Eight years ago, Tweet and his colleagues studied the stomach of a hadrosaur (Brachylophosaurus canadensis) nicknamed Leonardo. Hadrosaurs were plant eaters, also known as duck-billed dinosaurs. Inside Leo’s guts, the scientists saw dark, fingernail-sized flakes. At one time these may have been chewed leaves.
Among those flakes were squiggly white tracks. Now, Tweet and his colleagues have taken a closer look at the tracks. They found 280 of them in 19 samples of gut material. Up close, the tracks look like tunnels. Some are marked with thin lines, as if little hairs once brushed by.
The team also found chemical clues that mucus once lined the tunnels. Tweet thinks tiny worms with fine bristles might have once burrowed in Leonardo’s belly. They may have left behind a fossilized trail of slime.
“Dinosaurs didn’t walk the planet alone,” Fiorillo says. “They were part of an engaged and complicated ecosystem.”
Did other dinosaurs have worms, too? A closer look at more old fossils could reveal the answer, he says. The new paper “illustrates the beauty of the fossil record and how much more we still have to learn from it — if we just keep our eyes open.”
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dinosaur A term that means terrible lizard. These ancient reptiles lived from about 250 million years ago to roughly 65 million years ago. All descended from egg-laying reptiles known as archosaurs. Their descendants eventually split into two lines. They are distinguished by their hips. The lizard-hipped line became saurichians, such as two-footed theropods like T. rex and the lumbering four-footed Apatosaurus (once known as brontosaurus). A second line of so-called bird-hipped, or ornithischian dinosaurs, led to a widely differing group of animals that included the stegosaurs and duckbilled dinosaurs.
ecosystem A group of interacting living organisms — including microorganisms, plants and animals — and their physical environment within a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra.
fossil Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.
hadrosaur A duck-billed, plant-eating dinosaur that lived during the late Cretaceous Era.
host (in biology and medicine) The organism in which another lives. Humans may be a temporary host for food-poisoning germs or other infective agents.
journal (in science) A publication in which scientists share their research findings with the public. Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send out all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.
mean One of several measures of the “average size” of a data set. Most commonly used is the arithmetic mean, obtained by adding the data and dividing by the number of data points.
microscopic An adjective for things too small to be seen by the unaided eye. It takes a microscope to view such tiny objects, such as bacteria or other one-celled organisms.
mucus A slimy substance produced in the lungs, nose, digestive system and other parts of the body to protect against infection. Mucus is made mainly of water but also includes salt and proteins such as mucins. Some animals use mucus for other purposes, such as to move across the ground or to defend themselves against predators.
online A term that refers to things that can be found or done on the Internet.
paleontologist A scientist who specializes in studying fossils, the remains of ancient organisms.
paleontology The branch of science concerned with ancient, fossilized animals and plants. The scientists who study them are known as paleontologists .
parasite An organism that gets benefits from another species, called a host, but doesn’t provide it any benefits. Classic examples of parasites include ticks, fleas and tapeworms.
planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and it must have cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, it must be big enough to pull neighboring objects into the planet itself or to sling-shot them around the planet and off into outer space. Astronomers of the International Astronomical Union (IAU) created this three-part scientific definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU ruled that Pluto did not qualify. The solar system now includes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
tick A small eight-legged blood-sucking arthropod, related to spiders and mites. Although they look like bugs, these are not insects. They attach themselves to the skin of their host and feed on their blood. But in the process, they may spread any germs that could have been present in the blood of an earlier host.
tweet Message consisting of 140 or fewer characters that is available to people with an online Twitter account.
J. Tweet, K. Chin and A.A. Ekdale. Trace fossils of possible parasites inside the gut contents of a hadrosaurid dinosaur, Upper Cretaceous Judith River Formation. Journal of Paleontology. Published online June 16, 2016. doi: 10.1017/jpa.2016.43.