A remarkable trace fossil has given us a glimpse into the environmental conditions of a Jurassic seafloor. Ammonite fossils are common in Jurassic rocks but one particular ammonite is more unusual than most. In the horizontal layer of rock where it was found a 28 foot-long line of shallow grooves was found leading right up to the ammonite.
This long line of grooves in the rock has been interpreted as a drag mark because the streaks begins as just two grooves, then widen to become four grooves and then right before reaching the ammonite there are many more grooves before finally 11 grooves can be seen just an inch from the fossil itself. These grooves have been interpreted as the product of an ammonite shell gently being dragged across an ancient seafloor.
An artistic reconstruction of the floating ammonite leaving behind the drag mark. Illustration: James McKay
The picture that is painted by this…