This approach, using shell chemistry as a natural thermometer, is an established tool in geology. What makes this finding notable is where the fossils turned up: high on the Tibetan Plateau, a region now famous for its extreme altitude and harsh, cold conditions.

What does this mean for the Tibetan Plateau?

Today, the Tibetan Plateau is often called the "roof of the world." It hosts some of the highest terrain on Earth. But 94.5 million years ago, during the Cretaceous period, the picture was entirely different.

The fossils show the area was then covered by a shallow sea. Bottom-dwelling creatures thrived there in warm water, on a seafloor far removed from the towering mountains of the present day.

In other words, the plateau as we know it did not yet exist. The land that would eventually be pushed up to form the plateau was once a warm, shallow marine environment — closer to a tropical lagoon than to a frozen high-altitude desert.

How solid is the evidence?

The finding rests on two pillars: the fossilized creatures themselves and the seawater chemistry their shells recorded. Both point in the same direction.

The study, published as Wang et al. 2026, includes the fossil images in its supplementary information. The colorful preservation is unusual enough that the researchers highlighted it in announcing the work.

Still, as with any reconstruction of deep time, the conclusions carry uncertainty. Translating shell chemistry into a precise water temperature depends on assumptions about the seawater's original composition. The "hot tub" comparison is a broad characterization rather than an exact reading, and it should be read as such.

Why does 94.5 million years ago matter?

The date places these creatures in the Cretaceous period, a time when Earth's climate and geography differed sharply from today's. Seas covered regions that are now dry land, and the continents were still settling into their modern arrangement.

Fossils like these help fill in that picture. Each discovery of marine creatures on what is now high ground adds a data point to the long story of how Earth's surface changed — how seafloors became plateaus and shallow seas became mountains.

For the Tibetan Plateau, one of the most geologically significant features on the planet, evidence of a warm shallow sea adds a vivid chapter to that history: a time when the future "roof of the world" lay beneath sun-warmed water, and its seafloor teemed with clams and snails.