Ancient Seas

The water and sea basins we know today have been on Earth for much longer than the first humans. Clues from the ocean (in the form of seafloor or ice cores, and fossils) can help us learn about how the oceans reached their current state.

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Most people have never heard of the Hawaiian petrel , an endangered, crow-sized seabird that spends the majority of its life searching for food over the North Pacific Ocean. Nevertheless, this bird is no...
How long have jellyfish lived in the ocean? This jellyfish fossil is from the...
Like the modern nautilus, this relative of modern squid hunted from inside the...
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What makes a top predator? Razor-sharp teeth? Speed? Strength? Size? Who is the...

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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...

DIVE DEEPER

When you're standing in a museum surrounded by fossils, you can almost imagine drifting through time to when long-extinct...
During the late Cretaceous period, Kansas was covered by a vast sea. There, scientists have found fossils of Squalicorax sharks (also called crow sharks) that lived 70-80 million years ago. They were...
About 100 million years ago, during the heyday of the dinosaurs , reefs were built by mollusks called rudist clams . They looked very different from today's coral reefs . Discover more about the...
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...
Reaching almost three feet (one meter) long, Anomalocaris canadensis was enormous for this time period.
Editor's note: Read Nick's first blog post about "toothed" baleen whales to see what their team is excavating on Vancouver Island. We departed from Port Renfrew on Tuesday morning on the Michelle...
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—...
This illustration shows one old idea of what the ancient shark Helicoprion might have looked like. There once was room for many ideas—some more plausible than others—because the only fossils of the...
Globotruncana falsostuarti -- a foram that lived about 75 million years ago, during the Cretaceous Period, from southeastern Tanzania. By measuring the chemistry in the shell, scientists can estimate...
An archaeologist arranges a deep-sea core from off the coast of Britain. These cores are long cylinders of the earth's crust, drilled up from beneath the seafloor. When the cores shown here are...
Lenticulina secans -- this foram lives on the seafloor. This specimen was collected from ocean sediments in southeast Tanzania. It comes from a time over 92 million years ago when both the polar...
Come along as scientist Dr. Brendan Roark narrates a submersible dive to collect and study deep-sea corals. Roark studies deep-sea corals to understand the history of the ocean and past ocean...
Today, filter feeders like clams, sponges, krill, baleen whales, fishes, and many others fill the ocean, spending their days filtering and eating tiny particles from the water. But when did the first...
One of the ocean's tiniest organisms often does the most harm. Microscopic algae can grow rapidly to form harmful algal blooms (sometimes called "red tides"), which create unhealthy water conditions...
Sirenians , or seacows, are a group of marine mammals that include manatees and dugongs . Currently, only a single species of seacow is found anywhere in the world. However, the fossil record of...
This early whale was well suited to life at sea. But it also may have spent time on land. An ancestor of the right whale , Maiacetus lived 49-40 million years ago. It had flipper-like limbs and...
Fossils from the Cambrian period are found throughout the world. The Chengjiang fossil site in china is famous for containing about 196 species of fossils, many from the Cambrian period. The Burgess...
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...
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...
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