Tristan Hotham

Researcher of campaigns and platforms. Maker of other things.

Life on the moving map: 540 million years of animals on the drifting continents

Title card reading 'Life on the moving map' in black and red on cream paper, with the line: 409,895 fossil finds of 24 animal groups, from trilobites to hominids, put back where they lived on the drifting continents, 540 million years to today. Beside it a world map 200 million years ago showing the supercontinent Pangaea in sand on pale blue sea, dotted with coloured fossil finds.

Every fossil has two addresses: where it was dug up, and where the animal actually lived. I put 409,895 fossil finds, from trilobites to dinosaurs to our own family, back where they lived, on a map of the drifting continents that runs from 540 million years ago to today.

Explore the interactive version
Read the paper

A Tyrannosaurus found in Montana did not live in Montana, at least not in the Montana we know. Sixty-eight million years ago that patch of ground lay about 7 degrees further north, near the shore of a shallow sea that cut North America in two. Go back further and the shifts get dramatic. The fossils found in Britain tell the story: its Silurian sea creatures lived about 23 degrees south of the equator, the animals of its coal swamps, 300 to 320 million years ago, lived on the equator itself, and its early dinosaurs and ichthyosaurs at about 38 degrees north, the latitude of the Mediterranean today.

The Paleobiology Database, an enormous shared catalogue built up over decades by hundreds of palaeontologists, records both addresses for most fossil collections. Using the PALEOMAP plate model of Christopher Scotese, it works out where each collection was at the time its rocks were laid down. I took the records of 24 animal groups that people ask about (trilobites, sea scorpions, armoured fish, ammonites, sharks, insects, early amphibians, the mammals’ forerunners, marine reptiles, pterosaurs, dinosaurs, crocodiles, turtles, birds, mammals, whales, elephants and hominids) and drew them on PALEOMAP’s continents for 66 moments in time.

Six world maps in the Equal Earth projection showing the continents and fossil finds at 500, 300, 200, 150 and 66 million years ago and today. At 500 million years ago scattered continents are ringed with red trilobite dots; at 300 the continents are converging; at 200 nearly all land is one supercontinent, Pangaea; by 66 million years ago the Atlantic is open; today dots of mammals and birds cover the modern continents
The world at six moments, with fossil finds at the places they were laid down, coloured by group.

Watching Pangaea come and go

Press play on the interactive map and the continents drift past like slow weather. For the first half of the story they are scattered, with the giant southern continent of Gondwana lying across the South Pole. Then they converge, and by the Permian almost everything is jammed together into Pangaea. To put a number on it I measured how much of the land was joined into a single block at each moment. By 270 million years ago it was 88%, and it stayed above 85% for 90 million years, peaking at 90% around 180 million years ago. Then the supercontinent broke apart quickly: 50% by 150 million years ago, 23% by 100. Today the biggest block, Africa joined to Eurasia, holds 54%.

Line chart of the share of all land in the largest connected land mass from 540 million years ago to today: around 60 per cent through most of the Paleozoic, rising to above 85 per cent from 270 to 180 million years ago, peaking at 90 per cent, then falling to about 23 per cent by 100 million years ago and rising to 54 per cent today
How much of the land was joined in one block. Shaded: Pangaea, above 85%. Dashed lines: the five mass extinctions.

A caution: the outlines are today’s coastlines and continental blocks carried back in time by the plate model, not the ancient shorelines. Seas rose and fell by hundreds of metres, and at times flooded much of the continents, so plenty of ‘land’ on the map was really shallow sea. That is exactly where many of the oldest fossils formed.

Who ruled when

Counting fossils is not counting animals, so I asked a simpler question of each group: when was it most diverse in the record? Lay those answers side by side and the familiar parade of life appears. Trilobites lead the early seas, making up 57% of all genera from the Paleozoic era in these groups. Armoured fish have their Devonian moment. Early amphibians and the mammals’ forerunners flourish in the Permian and Triassic. Then come the marine reptiles and the dinosaurs, and finally the mammals, whales, elephants and hominids.

Swim-lane chart with one lane per animal group, from trilobites at the top to hominids at the bottom, each showing the number of genera per 5 million years scaled to its own peak. The lanes start and stop in a staircase from the Cambrian to today, with dashed lines at the five mass extinctions where several lanes end
When each group was at its most diverse: genera per 5 million years, each group scaled to its own peak.

One surprise: in the Mesozoic, the age of dinosaurs, the group with the most genera in this data is not the dinosaurs but the insects (42%). They are absurdly diverse, and a quarter of all insect finds come from just 50 extraordinary collections where delicate bodies were preserved.

Dinosaurs on one continent, then many

The data hold 20,231 finds of dinosaurs other than birds, in 1,588 genera. Their record grows through the Jurassic and explodes in the Late Cretaceous: the busiest 5 million years, 80 to 75 million years ago, has 316 genera, three quarters of the finds from North America, where rock of that age is unusually well exposed and well searched.

Stacked area chart of dinosaur genera per 5 million years from 240 to 60 million years ago, theropods in red, sauropods in plum and ornithischians in orange, low through the Triassic and Jurassic and peaking at over 300 genera around 75 to 80 million years ago, with birds as a dashed yellow line rising in the Cretaceous
Dinosaur genera through time, by group, with birds as a line.

Dinosaurs began on Pangaea, and you can see the supercontinent in where their genera turn up. Of the genera from the Late Triassic and Early Jurassic, when the land was one, 11% (about 1 in 9) are found on more than one of today’s continents. Of the Cretaceous genera, after the break-up, just 5% are (1 in 20). The separated continents grew their own casts: every tyrannosaur and horned dinosaur in the data comes from the northern continents, while most abelisaurs come from the southern ones and India.

Three small world maps of dinosaur finds at 210, 150 and 70 million years ago, showing Pangaea whole, then the central Atlantic opening, then the continents apart; below, a bar chart of the share of dinosaur genera found on two or more present-day continents, 10 to 16 per cent from the Late Triassic to the Late Jurassic and about 5 per cent in the Cretaceous, with a falling line for the share of land in the largest land mass
Dinosaurs on Pangaea and after it. Bars: genera found on more than one present-day continent. Line: share of land in the largest land mass.

A dot on this map is a place where rock of the right age reached the surface and someone went to look.

Five extinctions

The map marks the five great mass extinctions. A crude way to see them in this data is to ask what share of the genera around in the 10 million years before each one are never found again. At an ordinary moment that is 37%, because genera come and go and many are rarely found. The end-Permian, the ‘Great Dying’, stands out at 74%. At the end of the Cretaceous every genus of non-bird dinosaur, plesiosaur and mosasaur in the data disappears, and 97% of ammonites, while the insects barely notice. The end-Triassic hardly registers in these groups at all, a reminder of how coarse this lens is.

Five small bar charts, one per mass extinction, showing the share of genera in each animal group last seen in the 10 million years before it: trilobites 62 per cent at the end-Ordovician; ammonites, trilobites and armoured fish 65 to 70 per cent in the Late Devonian; early synapsids 87 and ammonites 84 per cent at the end-Permian; ammonites 74 per cent at the end-Triassic; and 100 per cent of non-bird dinosaurs, plesiosaurs and mosasaurs at the end-Cretaceous
Share of genera last seen before each extinction, by group. Dashed: the same measure at ordinary times.

A map of where palaeontologists dig

The honest headline is about the record itself. North America and Europe hold 32% of the world’s land but 66% of the finds here, and the United States alone 28%. Africa has 8%. The ancient continents look busiest where today’s have the most museums, universities and road cuttings. An empty ocean or continent on the map usually means no rock of that age at the surface, or nobody looking, not an empty world.

Left, bar chart of fossil occurrences by present-day continent: North America 36 per cent, Europe 30, Asia 16, Africa 8.5, South America 6.5, Oceania 3, Antarctica under 1. Right, a jagged line of North America and Europe's share of finds per 5 million years, mostly between 50 and 90 per cent, far above a dashed line at 32 per cent for their share of the land
Where the finds are today, and North America and Europe’s share through time.

How I did this

I downloaded every occurrence of 23 named groups from the Paleobiology Database’s data service (480,977 rows), with palaeo-coordinates from the PALEOMAP model at each collection’s midpoint age. The groups overlap, so each record is kept once in its most specific group, and I fixed three names that reach further than intended: an insect also called Proboscidea, the frogs and salamanders that the database files inside the temnospondyls, and some birds filed as theropods. Ages are the midpoints of each collection’s age range; collections dated only to within more than 25 million years are left out. That leaves 409,895 occurrences in 98,147 collections. The continents are PALEOMAP outlines from the GPlates Web Service, the same model as the fossil positions, simplified for the web and drawn in the Equal Earth projection. On the map, finds are binned into 1 degree squares of ancient latitude and longitude. The paper has the details and every caveat.

Explore the interactive version
Read the paper
Data and code

Notes and sources

  • The Paleobiology Database (paleobiodb.org), data accessed 2026, via the data service version 1.2. CC BY 4.0.
  • PALEOMAP plate model and coastlines, C. R. Scotese, PALEOMAP Project, reconstructed with the GPlates Web Service (EarthByte group, University of Sydney). I could not check PALEOMAP’s own reuse terms while building this, so the outlines are credited in full; please check them before reusing the outlines.
  • Natural Earth countries and provinces (public domain), for present-day places.
  • Geological time scale after the International Commission on Stratigraphy’s chart, rounded.
  • I wrote the text, with drafting and editing assistance from Claude (Anthropic), which also helped prepare the analysis code. I reviewed and checked all text and results.

Tristan Hotham

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