Originally assigned to the living genus Limulus, they are related to and look virtually identical to modern horseshoe crabs.

Other species assigned to Mesolimulus have been recorded spanning over 140 million years from the Middle Triassic to Late Cretaceous from England, Spain, Siberia and Morocco.

Eventually they were correctly identified as arthropod footprints and named Kouphichnium walchi, as proved by some remarkable 'death traces' showing a Mesolimulus circling round on itself before dying.

The last leg of more advanced horseshoe crabs is modified into a so-called 'pusher' which consists of four plates at the tip which push against the soft sediment rather like a snow-shoe.

Fossils preserved in Solnhofen limestone are unusual because soft body parts and skeletons are clearly represented.