Sauropods, the long-neck dinosaurs that towered over the Jurassic landscape, grew up next to lots of hungry neighbors. These herbivores were vulnerable hatchlings, and according to a new study, they may have helped sustain entire predator populations.
By reconstructing a food web from fossils in Colorado’s Morrison Formation, researchers found that baby and very young sauropods were a central food source for large meat-eating dinosaurs such as Allosaurus and Torvosaurus. The study, published in the New Mexico Museum of Natural History and Science Bulletin, maps thousands of feeding relationships from about 150 million years ago.
“Life was cheap in this ecosystem, and the lives of predators such as the Allosaurus were likely fueled by the consumption of these baby sauropods,” said Cassius Morrison, lead author, in a press release.
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Reconstructing the Jurassic Food Web
To piece together what the Morrison Formation ecosystem looked like, the researchers focused on fossils from the Dry Mesa Dinosaur Quarry in Colorado. The site preserves at least six species of sauropods, including Diplodocus, Brachiosaurus, and Apatosaurus, along with large predators and smaller animals.
The fossils were deposited over a relatively short window of time, likely less than 10,000 years. That narrow window gives researchers an unusually focused view of a Late Jurassic ecosystem.
They used body-size estimates, microscopic tooth wear, chemical signatures preserved in bone, and fossilized stomach contents. Then they entered that information into ecological modeling software typically used to study modern ecosystems.
The result was a network of more than 12,000 potential food chains. Sauropods are connected to more species than any other herbivore group in the quarry, linking to a wide range of plants and predators.
“Sauropods had a dramatic impact on their ecosystem. Our study allows us to measure and quantify the role they had for the first time,” said Morrison.
Small, Unprotected, and Abundant
As adults, sauropods were immense. Their eggs, by contrast, were only about a foot across.
“Adult sauropods such as the Diplodocus and Brachiosaurus were longer than a blue whale. When they walked, the earth would shake. Their eggs, though, were just a foot wide, and once hatched, their offspring would take many years to grow,” said Morrison.
Despite that size, the young were not closely guarded. Evidence shows hatchlings were left on their own. Given the scale of adult sauropods, tending nests could have risked crushing the eggs, making hands-off reproduction the better strategy.
“Some Allosaurus fossils show signs of quite horrific injuries — for instance caused by the spiked tail of a Stegosaurus – that had healed and some which hadn’t. But an abundance of easy prey in the form of young sauropods may have allowed injured allosaurs to survive,” said study co-author William Hurt in a press release.
Changing Pressures Over Time
By the time Tyrannosaurus rex appeared roughly 70 million years later, sauropods were less common in North America. Predators faced prey such as Triceratops, which were larger and better defended.
With fewer sauropods available, later predators may have experienced stronger pressure to develop powerful bites, larger bodies, and improved vision.
“Reconstructing food webs means we can more easily compare dinosaur ecosystems across different periods. It helps us to understand evolutionary pressures and why dinosaurs might have evolved in the way they did,” Morrison added.
By stepping back from individual fossils and examining the ecosystem as a whole, the researchers argue that sauropods influenced Jurassic life at every stage of growth. Their enormous adults dominated the landscape, but their exposed young may have quietly sustained it.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a recent study published in New Mexico Museum of Natural History and Science Bulletin: “Here, Size Is No Accident”: A Novel Food Web Analysis of the Dry Mesa Dinosaur Quarry and Ecological Impact of Morrison Formation Sauropod Fauna
