Triassic Water

Is the water we drink dinosaur water?

Almost certainly, yes. Earth has been recycling an enormous ancient supply of water for billions of years, and dinosaurs drank from that supply for more than 175.5 million years. The individual water molecules have been broken apart and rebuilt countless times, so we cannot follow one molecule from a dinosaur to your glass — but some of the hydrogen and oxygen atoms in the water you drink almost certainly passed through the dinosaur-era water cycle.

Start by counting the glass

A 250 ml glass of water weighs about 250 grams. Divide that by the weight of one mole of water, multiply by the number of molecules in a mole, and you get the number of water molecules you are holding:

Water molecules in one 250 ml glass

8,360,000,000,000,000,000,000,000

Glasses that size in all the water on Earth

5,540,000,000,000,000,000,000

That is about 8 million million million million. Now count the other way. All the water on Earth — every ocean, ice sheet, cloud, river and drop of groundwater — comes to about 1,386,000,000 cubic kilometres. That is enough to fill about 5,540,000,000,000,000,000,000 glasses.

Read those two numbers again. There are roughly a thousand times more molecules in one glass than there are glasses of water on the whole planet. Everything else on this page follows from that.

So how little does one dinosaur have to drink?

One glassful of water, drunk by one dinosaur 66 million years ago, then peed out and mixed back into Earth’s water. If it mixed evenly, about 1,507 molecules of that one drink are in the glass you poured today.

One animal. One drink. And that is before you remember that millions of dinosaurs drank every day for over 175.5 million years.

How long were dinosaurs drinking?

Longer than almost anyone guesses. These are the dates the Paleobiology Database holds — the fossils scientists have actually dug up and recorded, not an estimate of ours.

247–241.5 million years ago
The oldest fossils the database places among the dinosaurs. From here on, something dinosaur-shaped is drinking from rivers every single day.
83.6–66 million years ago
Tyrannosaurus rex: 70 recorded fossil finds, all from the Campanian to Maastrichtian — the very end of the story. T. rex is closer in time to you than to the oldest dinosaurs.
66 million years ago
The end of the Cretaceous, and the end of every dinosaur except the birds. That is at least 175.5 million years of dinosaurs drinking, and the water carried on regardless.
Today
The database still records the dinosaurs as a living group, because birds are dinosaurs — its last-appearance date for them is 0 million years ago, which is another way of writing “today”. A pigeon at a puddle is a dinosaur having a drink, this afternoon.

Did dinosaurs drink the same water we drink?

Yes — dinosaurs drank from rivers, lakes and puddles, and Earth has been recycling its water ever since. Not the identical molecules: the same enormous, ancient supply has been cycling through Earth for billions of years.

What was the water doing all that time?

Going round. Water evaporates from the sea, falls as rain, runs down rivers, soaks into the ground, gets drunk by animals and plants, comes back out, and evaporates again. Earth has been recycling an enormous ancient supply of water for billions of years.

That is why the amount of water on Earth barely changes. It is the same supply, used over and over — which is why a glassful drunk 66 million years ago did not vanish. It went back into the loop.

A labelled diagram of the global water cycle, showing evaporation from oceans, clouds and precipitation, rivers running to the sea, groundwater below the surface, and the ways people take and return water.
Diagram — a drawing that explains how something worksThe water cycle, as the U.S. Geological Survey draws it: water evaporating from the sea, falling as rain and snow, running down rivers, soaking into the ground, and going round again. The same loop that has been running since long before the dinosaurs.Released by the USGS in 2022. This version of the diagram deliberately includes human water use — where people store, move and pollute water — which older water cycle diagrams left out.Credit: U.S. Geological Survey · U.S. Public Domain · Museum record
An illustrated shallow river across a floodplain under overcast light, with several large plant-eating dinosaurs standing in the shallows drinking, reflected in the still water.
AI reconstruction — not a photographAn artist's impression of dinosaurs drinking from a river in the Late Cretaceous. It illustrates the idea on this page — that dinosaurs drank from rivers, lakes and puddles — rather than recording any particular animal, place or day.No species is named here, and none should be: the animals are a generator's impression of Late Cretaceous plant-eaters, not identifications. The page's own fossil claims come from the Paleobiology Database, never from this picture.Shutterstock AI/Shutterstock.com · Shutterstock Standard License · Museum record

And yes — that includes the pee

Pee is mostly water, and the water cycle has been cleaning and re-using every drop since long before the dinosaurs. Rain, river, sea, dinosaur, rain again: water like the water in your tap has travelled through every part of this cycle countless times, and what comes out of the tap is clean now. That is what the water cycle does — and it is the same reason water that was once sewage can be treated, returned to a river and safely drunk again downstream.

Who drank it?

Someone real. In the rocks 19.4 km from Denver, palaeontologists dug up an Apatosaurus louisae — a long-necked plant-eater the size of a house. It was first described in print under a different name, Apatosaurus laticollis, which is normal: names get revised as scientists learn more.

The rock it came out of is the Morrison Formation, Brushy Basin Member, which the Paleobiology Database places somewhere between 154.8 and 143.1 million years ago. That is the database’s bracket for this find rather than a measured age for the rock, and it is a wide one — geologists who have dated the Morrison directly give it a narrower window. The Paleobiology Database records the environment there as “channel” — a river channel. So this animal was buried in a river, and rivers are where you drink.

A mounted skeleton of a long-necked, long-tailed sauropod dinosaur filling a museum hall, with a painted forest behind it and a person standing at the right for scale.
Real photographApatosaurus louisae — specimen CM 3018, the skeleton this species was first described from. It stands on public display at the Carnegie Museum of Natural History in Pittsburgh; the person at the right of the picture gives you the scale.This is not the fossil above. It is a different Apatosaurus louisae — CM 3018, dug from the same Morrison Formation but at Carnegie Quarry in Utah, and photographed on display in Pittsburgh. The one this page is about is still in the ground near Denver, Colorado.The animal was dug out of the Morrison Formation at Carnegie Quarry, in what is now Dinosaur National Monument, Utah. Photographed on display in Pittsburgh in 2011.James St. John, CC BY 2.0, via Wikimedia Commons · CC BY 2.0 · Museum record

Careful with the wording, because it matters: this fossil was dug up 19.4 km away, and that is all we can say. It does not mean a dinosaur stood where Denver stands now. We show the position rounded to 0.1° — about 11 km — because our map is for children, not for anyone hunting the site.

What changed, and what did not

Almost everything changed. Continents slid apart, seas flooded whole countries and drained away again, mountains went up, ice came and went. The map of Earth from the dinosaurs’ time would be unrecognisable to you.

The water stayed. It moved — endlessly — but Earth kept hold of nearly all of it. The supply that filled those vanished seas is essentially the supply filling the sea today, and the reservoir your tap water comes from.

One honest wrinkle: individual water molecules do get taken apart and rebuilt. Plants split water when they photosynthesise, and living things make new water when they breathe. So “the same water” is really the same endlessly recycled supply of hydrogen and oxygen, not the same unbroken set of molecules. That does not weaken the answer — it is why we count molecules rather than following one.

Try it with your own glass

Pick a glass and watch both numbers move. The molecule count grows with the glass. The dinosaur’s share grows faster, because in this sum the dinosaur is drinking a glassful the same size as yours.

Pick a glass
Water molecules in it
8,360,000,000,000,000,000,000,000
About 8 million million million million.
From one dinosaur’s single drink
1,507
molecules, if one dinosaur drank a 250 ml glassful and it mixed evenly through all Earth’s water.

For teachers

For school

  • A 250 ml glass holds roughly 8,360,000,000,000,000,000,000,000 water molecules.
  • All Earth’s water would fill about 5,540,000,000,000,000,000,000 glasses that size — around a thousand times FEWER glasses than there are molecules in one of them.
  • The Paleobiology Database holds 37,839 dinosaur fossil records, the oldest from rock dated between 247 and 241.5 million years old.

Classroom prompt

There are more molecules in one glass of water than there are glasses of water on Earth. Ask the class to explain, in their own words, why that single fact settles the question — before showing them the sum.

Ages: the answer and the pee block work from about seven. The arithmetic — powers of ten, dividing very large numbers — suits about ten upwards. Nothing on this page needs a calculator to follow, only patience with zeros.

How sure are we?

These figures are estimates built from measured quantities. The journey of one particular water molecule has never been reconstructed, and never can be — no experiment can follow a single molecule for 66 million years — and Earth’s water is not perfectly mixed: some has been locked in ice sheets or deep underground for a very long time. Water molecules are also unmade and remade, as plants split them apart and breathing makes new ones. That is why the honest answer is almost certainly, and not definitely.

Two things on this page are assumptions we chose, not measurements: An ordinary drinking glass, 250 ml. Stated on the page, and the calculator lets a reader pick a different one. And: We take one litre of water to weigh exactly one kilogram. The real figure moves slightly with temperature; no published value is cited here because none is needed at this precision. The reveal above also assumes even mixing, which no ocean truly achieves.

Sources

  • Fossil occurrence data from the Paleobiology Database (https://paleobiodb.org), released under CC0 1.0. Licence.
  • Credit: U.S. Geological Survey Licence.
  • Mohr, P. J., Newell, D. B., Taylor, B. N., and Tiesinga, E. (2024), The NIST Reference on Constants, Units, and Uncertainty — 2022 CODATA recommended values, NIST Standard Reference Database 121, National Institute of Standards and Technology, https://physics.nist.gov/cuu/Constants/ (Accessed 2026-08-28) Licence.
  • Atomic weights of hydrogen and oxygen: © CIAAW, 2007-2024 — Commission on Isotopic Abundances and Atomic Weights (IUPAC), Abridged Standard Atomic Weights, https://www.ciaaw.org/abridged-atomic-weights.htm (accessed 2026-08-28) Licence.
  • End-Cretaceous boundary age: International Chronostratigraphic Chart data (version v2026-06.5), © International Commission on Stratigraphy, licensed CC BY 4.0, https://github.com/i-c-stratigraphy/chart. Cite: Cohen K, Harper D, Gibbard P, Car N. The ICS international chronostratigraphic chart this decade. Episodes 2025;48:105-115. https://doi.org/10.18814/epiiugs/2025/025001 Licence.
  • The end-Cretaceous age is cited directly from the chart data of the International Chronostratigraphic Timescale. The Paleobiology Database, whose own timescale is that same chart, agrees with it. PBDB publishes no dataset version string; the data-service path (data1.2) and the datainfo access_time bound this claim.

Figures version 2, computed . The Paleobiology Database was read at Fri 2026-08-28 00:40:13 GMT.

Where next

Back to Triassic Water — the rest of the site is being built dataset by dataset, and links appear here as pages go live, not before.