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What makes a top predator? Razor-sharp teeth? Speed? Strength? Size? Who is the most fearsome hunter? It depends on where and when you look.
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...
Sirenians , or seacows, are a group of marine mammals that include manatees and...

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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 webbed feet, like modern seals. But...
Offshore Peru, during the Eocene (~56-34 million years ago), showing three...
These "elevator" rudists, an ancient bivalve, used one long heavy valve to...

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Whales swim, but their ancestors walked. Whales are mammals (like us) whose ancestors lived on land. Life probably began in...
These "elevator" rudists, an ancient bivalve, used one long heavy valve to anchor themselves in the sediment. They used their tentacles (shown here in pink) to filter food from the sea water. And...
400 to 1,000 year old bones from an endangered seabird, the Hawaiian petrel. Bones such as these provide a window into the lives of seabirds before and after human arrival in the open ocean...
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...
Opabinia was a strange looking creature: it had five mushroom-like eyes that allowed it to see predators approaching from many directions.
The whales that we see in today's world can broadly be split into two groups: those with teeth (odontocetes), and those that have baleen (mysticetes) instead of teeth. These two groups share a common...
How long have jellyfish lived in the ocean? This jellyfish fossil is from the Cambrian period, more than 500 million years ago. It was found buried in Utah —an area that used to be underwater,...
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—...
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...
Monodontids, the group of whales that includes the belugas and narwhals swimming our ocean today, are emblematic symbols of the Arctic. However, their fossil record, although scarce, suggests that...
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.
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...
A scientific illustration of the most powerful fish of its time, Carcharodon megalodon , which swam the ocean 30 million years ago. This shark may have reached a size of 20 meters/66 feet. Meet other...
Whales swim, but their ancestors walked. Whales are mammals (like us) whose ancestors lived on land. Life probably began in the ocean and then evolved to colonize the land. Yet the whale’s ancestors...
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...
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...
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...
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...
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