A Vacation Photo on Facebook Turned Out to Show a 120-Million-Year-Old Dinosaur Footprint

A 32-year-old tourist named Pichai Prathetsena posted a holiday photo to a Facebook group called "What Is This Creature?" and accidentally discovered a dinosaur footprint around 120 million years old. He had taken the picture at Phu Phra Bat National Park in Thailand, where a deep dent in the ground had caught his eye.

The dent turned out to be one of six

Someone in the government saw the photo, and experts were soon at the park. They measured the print at 11.4 inches by 10.2 inches, with three toes. It was not alone: it turned out to be one of six footprints at the site, all of them dating back to the Early Cretaceous, the stretch of time the 120-million-year figure comes from.

The park was closed while the area was examined properly. That is a lot of attention for a shape in the dirt, but the shape is the whole point.

Why a hole in the ground is worth studying

Experts call finds like this trace fossils. The phrase sounds technical, but the idea is simple: these are not bones or teeth, they are marks left behind by a living animal. Soft ground took the impression of a foot, then hardened over time, holding the shape like a cast.

Because the prints are deep and well spaced, they carry information about the animal that made them. The size and depth of the impressions, and the distance between them, hint at its weight, its size, how long its stride was and how it walked.

In this case the picture that emerges is of a meat-eating dinosaur, a two-legged hunter of a kind called a theropod. Its hind legs are estimated at around 4 feet 8 inches, and its total length at more than 20 feet. That puts it in the same size class as Siamotyrannus isanensis, a dinosaur estimated at one ton that was found in Thailand before. Working out the exact species will take more research.

A first for Udon Thani Province

Thailand has been yielding dinosaur footprints for decades. So far 25 dinosaur species have been found in the country, and 13 of them have not been found anywhere else. Many of those discoveries have been linked to members of the public who help with science rather than to professional fossil hunters.

These six prints are still a first: they are the first prints of a meat-eating dinosaur found in Udon Thani Province. Government agencies are now working to protect the site from further erosion and water damage, and the Thai Department of Mineral Resources has said on Facebook that it could be developed into a hub for geological and fossil research.

All of which started with one photo, posted to a group whose name asks what a creature is. In this case, the answer was a dinosaur.