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A Field Guide to the Dig

Every day in Fossil Digger you drill down through six layers of the past. Here's what's in each one — the eras themselves, and the real creatures buried in them. The deeper you reach, the older and stranger the find.

Topsoil
The Ice Age
After the Asteroid
The Cretaceous
The Jurassic
Deep Time

Topsoil

Recent · 0–100 m down

The first strokes of the drill don't hit anything ancient at all — just the stuff we dropped ourselves. The topsoil is the human layer: a few centimetres to a few metres of recent earth that holds whatever fell out of pockets, bins and backyards. It's the shallowest dig and the easiest to reach, which is exactly why it's full of junk rather than treasure. Finding a fossil this close to the surface is almost impossible; finding a lost phone is not.

Bottle capCrown caps have had exactly 21 teeth since 1892. Any fewer and they leak.
Glass marbleMass-produced from 1915 on a machine originally built for making bottles.
A 1987 car keyKeys got transponder chips in the mid-90s. Before that, one key in twenty opened your car.
Nokia 3310126 million sold. Still sets off metal detectors.

The Ice Age

Pleistocene · 2.6 million – 12,000 years ago

Past the topsoil the temperature drops and you reach the Pleistocene — the last great Ice Age, a two-and-a-half-million-year run of advancing and retreating glaciers. This is the age of megafauna: oversized, cold-adapted mammals and birds that shared the world with the first humans. Most of them vanished as the ice pulled back and people spread out, which makes this layer a graveyard of giants that only just missed our own history.

Woolly mammothThe last ones died on Wrangel Island around 1650 BC — centuries after the Great Pyramid was finished.
Sabre-tooth catSmilodon's 18 cm canines were startlingly fragile — built for one precise throat bite, not brawling.
Giant ground slothMegatherium stood four metres tall. Its claws were so long it walked on the sides of its feet.
Woolly rhinoIts front horn was a flat blade, worn smooth from sweeping snow off grass.
MoaNine species, and not one had wings — not even vestigial bones. Gone within 150 years of human arrival in New Zealand.
Haast's eagleThe largest eagle that ever lived. Fifteen kilos, and it hunted moa four times its own weight.

After the Asteroid

Palaeogene · 66–23 million years ago

Deeper still, you break into the aftermath of the worst day in Earth's history. Sixty-six million years ago an asteroid ended the dinosaurs, and the Palaeogene is the long recovery that followed. With the giant reptiles gone, mammals and birds inherited the planet and promptly got enormous — whales learned to swim, penguins grew taller than people, and snakes reached lengths that only a hotter world could support.

MegalodonTeeth up to 18 cm. We have never found a complete skeleton — the rest of it was cartilage.
Kairuku, the giant penguin1.3 metres tall, waddling around what is now Otago, 27 million years ago.
TitanoboaThirteen metres, a tonne in weight. It needed an average temperature of 30°C just to function.
ParaceratheriumThe largest land mammal ever — a hornless rhino standing five metres at the shoulder.
BasilosaurusA twenty-metre whale with tiny useless back legs, left over from its life on land.

The Cretaceous

145–66 million years ago

Now you're into the dinosaurs proper. The Cretaceous was the last and longest act of their reign — the world of T. rex and Triceratops, of the first flowering plants and the first bees to pollinate them. It ended abruptly at the top of this layer, with the asteroid, so digging up through it is digging back into the final, richest chapter of the age of reptiles.

Tyrannosaurus rexA bite of roughly 35,000 newtons — the hardest bite of any land animal that has ever lived.
TriceratopsThe frill was threaded with blood vessels. Probably display and heat control, not armour.
VelociraptorTurkey-sized and feathered. The ones in the films are closer to Deinonychus.
AnkylosaurusEven its eyelids were armoured, and the tail club hit hard enough to break bone.
SpinosaurusThe first dinosaur known to swim — dense bones, a paddle tail and a crocodile's snout.

The Jurassic

201–145 million years ago

The Jurassic is the postcard age of dinosaurs — long-necked giants on the plains, plated grazers, and the very first birds taking to the air from among the small feathered dinosaurs. The oceans were full too, patrolled by long-necked plesiosaurs. Reaching this layer takes a real dig; the finds here are old enough that only a strong run gets you down to them.

StegosaurusIts brain was the size of a lime. The plates were full of blood vessels.
AmmoniteThey lasted 340 million years and died out with the dinosaurs. The shell is a near-perfect logarithmic spiral.
ArchaeopteryxTeeth, claws partway along its wings, a bony tail — and proper asymmetric flight feathers.
PlesiosaurUp to 76 vertebrae in the neck. A giraffe manages with seven.

Deep Time

Palaeozoic · 539–359 million years ago

The bottom of the shaft is the oldest and the strangest. Deep Time reaches back to the Palaeozoic, when complex life first exploded across the seas and nothing yet lived on land. These are the experiments evolution tried before it settled on anything familiar — armoured worms, five-eyed swimmers, the first eyes and the first jaws. Hauling something up from here is the rarest dig in the game, and the find is usually older than almost everything else on Earth.

TrilobiteThe first complex eyes on Earth, grown from calcite crystal. They saw through stone.
AnomalocarisThe first apex predator — a metre long, when almost nothing else was bigger than your thumb.
HallucigeniaReconstructed upside down and back to front for fifteen years. Nobody could tell which end was which.
DunkleosteusNo teeth at all — self-sharpening bony blades, closing with the force of a modern crocodile.

Go and dig one up

Every creature here is something you can actually haul out of the ground in the game — one fresh dig a day, scored on how rare your answers are rather than whether they're right. New to it? Start with How to Play, then open the dig.

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