The ink sacs belonged to a cephalopod, the group that includes squid, octopus and cuttlefish, 160 million years ago, during the Jurassic era. The molecular structure of the ancient ink is surprisingly similar to that of modern cuttlefish Sepia officinalis, said study researcher John Simon, a professor of chemistry at the University of Virginia.

Previous studies have turned up tiny structures in everything from fossil fish eyes to dinosaur feathers containing the dark brown or black pigment melanin. But it can be tough to tell pigment structures, called melanosomes, from fossilized bacteria. Simon and his colleagues used a barrage of chemical tests to examine two fossil ink sacs found in the United Kingdom. These tests gave them a remarkably detailed look at the molecular makeup of the ink sacs' contents. 

 

 The ink sacs belonged to a cephalopod, the group that includes squid, octopus and cuttlefish, 160 million years ago, during the Jurassic era. The molecular structure of the ancient ink is surprisingly similar to that of modern cuttlefish Sepia officinalis, said study researcher John Simon, a professor of chemistry at the University of Virginia.