A historic drought in Texas has dried up a river flowing through Dinosaur Valley State Park, exposing tracks from giant reptiles that lived some 113 million years ago.
Photos posted on Facebook show three-toed footprints leading down a dry tree-lined riverbed, south-west of Dallas, in the southern US state.
It is "one of the longest dinosaur trackways in the world," a caption on one the posts says.
Stephanie Salinas Garcia of the Texas Parks and Wildlife Department said the dry weather had made the tracks visible.
"Due to the excessive drought conditions this past summer, the river dried up completely in most locations, allowing for more tracks to be uncovered here in the park," she said.
"Under normal river conditions, these newer tracks are under water and are commonly filled in with sediment, making them buried and not as visible," Ms Garcia said.
Most of the recently revealed tracks were made by Acrocanthosaurus, a bipedal predator that weighed nearly 6.35 tonnes as an adult and stood 4.5 meters tall.
Another dinosaur, Sauroposeidon, also left tracks in the park. The long-necked herbivore was 18 metres tall and weighed 40 tonnes in adulthood.
The inland state park was once on the edge of an ancient ocean, and dinosaurs left footprints in the mud.
However, rain is in the forecast.
"While they will soon be buried again by the rain and the river, Dinosaur Valley State Park will continue to protect these 113 million-year-old tracks not only for present, but future generations," Ms Garcia said.
AFP contributed reporting