Copepods, tiny shrimp-like crustaceans, are the creatures that today form the main food source of whales. Typically these creatures are 1–2 mm in length1. They are the most numerous of the multicellular animals on Earth and even outnumber insects!
Copepods live in natural and man-made aquatic environments, from salt- to fresh water, and from the deepest oceanic abysses to the high altitude lakes of the Himalayas.
However, because of their small size and fragility, they fossilise poorly. Their fossil record consists of one example from rocks of Cretaceous age (about 115 million years old) and a few from the Miocene (about 14 million years old). As a result of recent research, they are now known to have been around more than twice as long as previously thought.
During a field trip to Oman, a piece of fossil pitch (bitumen or solid oil) was found in a ancient glacial deposit about 300 million years old. The piece of pitch was originally thought to be some kind of volcanic rock, but then was realised to be solid oil because it was so light.
The piece of pitch was taken to the BGS laboratories where it was treated with various chemicals, to try to dissolve it, to see what was inside. All along the geologists thought it might be like a piece of opaque amber and might contain insects or other interesting animals from 300 million years ago.
What we found was amazing — a huge number of tiny fragments that at first we had no idea about. After several years of careful research it emerged that some of the fragments were of copepods.
The striking thing is that the oldest copepods before this discovery were from rocks 115 million years old.
This changes the way that biologists think about copepods and extends their fossil record by 188 million years.
Copepods are minute marine or freshwater crustaceans; they are related to such things as lobsters, crabs, shrimps, woodlice, barnacles and water fleas.
"Copepod abundance on the surface layers of the oceans creates the world's largest carbon sink, absorbing about two billion tonnes of carbon a year, the equivalent to perhaps a third of human carbon emissions."
The name copepod is derived2 from the Greek; kope = 'oar' and podos = 'foot' 1. Hence copepod, or oar-footed, referring to the pair of swimming legs, found on the same division of the body, that move together like the oars of a sculling boat.
For further information about the research see Crustaceans from bitumen clast in Carboniferous glacial diamictite extend fossil record of copepods
or contact Mike Stephenson.