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Like the modern nautilus, this relative of modern squid hunted from inside the safe haven of a protective shell. Ammonites went extinct around the same time as the dinosaurs—65 million years ago. Find more...
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What makes a top predator? Razor-sharp teeth? Speed? Strength? Size? Who is the...
About 100 million years ago , during the heyday of the dinosaurs, reefs were...
For a long time, scientists thought that some small tentacled fossils were...

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Offshore Peru, during the Eocene (~56-34 million years ago), showing three archaeocetes (ancient whales), along with a previously described fossil penguin. Top to bottom: Perudyptes devriesi , unnamed protocetid, Ocucajea...
These "elevator" rudists, an ancient bivalve, used one long heavy valve to...
How long have jellyfish lived in the ocean? This jellyfish fossil is from...

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When you're standing in a museum surrounded by fossils, you can almost imagine drifting through time to when long-extinct...
Earth’s first animals had soft bodies. This illustration shows a community of soft-bodied Ediacaran (edi-A-karan) animals. Some species resemble living ocean creatures. Others are unlike any known...
The great predator Hurdia victoria’s prey consisted of trilobites and other smaller animals crawling on the seafloor.
Opabinia was a strange looking creature: it had five mushroom-like eyes that allowed it to see predators approaching from many directions.
Evidence shows that life probably began in the ocean at least 3.5 billion years ago. Photosynthesis began more than 2.5 billion years ago—the Great Oxidation Event. But it took hundreds of millions...
The peaceful Archaeocyatha lived during the most recent part of the Cambrian period. They separated into many families and were the Earth’s first reef-building animals.
A life-sized model suspended over visitors at the San Diego Natural History Museum shows what an ancient shark, the Giant Megatooth ( Carcharodon megalodon ), might have looked like. More about the...
Long before great white sharks appeared, much larger ancestors roamed the ocean. This giant ancient shark -- the Giant Megatooth ( Carcharodon megalodon ) -- was probably big enough to eat a whale.
This rendering shows life at the end of the Cretaceous Period, before the impact of a 6.2 mi (10 km) asteroid triggered mass extinctions on land and sea. Dinosaurs are the most famous victims of the...
This illustration shows the edge of a warm inland sea during the Cretaceous Period, heyday of the dinosaurs. Constantly shifting sediment supported new groups of organisms, including rudist clams—...
Humans are late arrivals on Earth. For nearly 75% of Earth’s history, life consisted of single-celled microbes without a nucleus (prokaryotes). Volcanoes and erosion sculpted Earth 3.5 billion years...
Rudist clams are mollusks that went extinct about 65 million years ago. They were the reef builders of the Cretaceous Period, the heyday of the dinosaurs. Today corals have taken over the role...
Crinoids (echinoderms related to sea stars and sea urchins) dominate the Paleozoic shallow water habitat in this illustration. They evolved a variety of stalk heights, which enabled them to capture...
Hantkenina mexicana -- a foram with elongated shell chambers that lived between 45-49 million years ago, during the Eocene Epoch. This specimen is from marine sediments that were drilled in the...
Offshore Peru, during the Eocene (~56-34 million years ago), showing three archaeocetes (ancient whales), along with a previously described fossil penguin. Top to bottom: Perudyptes devriesi ,...
This early whale was well suited to life at sea. But it also lived on land. An ancestor of the right whale , Maiacetus lived 49-40 million years ago. It had flipper-like limbs and webbed feet, like...
Reaching almost three feet (one meter) long, Anomalocaris canadensis was enormous for this time period.
Not all fossils from the Cambrian period became amulets; instead the extinct Hallucigenia sparsa was notable for its spines.
The Ottoia prolifica has proven that cannibalism did exist in the Cambrian period since there have been portions of one Ottoia prolifica found in another specimen’s gut.
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