A fossilized horseshoe crab and its death track were discovered near the village of Wintershof, Bavaria, Germany, in 2002; the layer of limestone in which they were found dates to between about 150 million and 145 million years ago. The 32-foot (9.7 meter)-long trackway was likely made after the crab was washed into a toxic lagoon during a harsh storm, researchers reported Aug. 29, 2012 in the journal Ichnos. (The bottom sketch is an interpretation of the death track.)
Here, the preserved Mesolimulus walchi specimen, measuring 5 inches (12.7 cm) long and 2.7 in. (6.9 cm) wide, and found at the end of the death trackway in Germany. The horseshoe crab's size, along with comparisons with other individuals discovered in the area, suggests it was just a juvenile when it died.
The researchers divided the trackway into five slabs, A through E, with the first showing where the horseshoe crab likely landed after being pushed into the ancient lagoon.
Throughout parts of the trackway, imprints suggest various movements, including gentle meandering, sudden angular turns of the body and straight walking locomotion.
In the second part of the trackway (B), the researchers noticed the horseshoe crab made two 90-degree turns, making small partial spirals and using the front of its body, called the prosoma, to do these spins. Shown here, the second partial spiral, showing drag marks made by the telson and the use of its legs and prosoma.
The third slab of the death trackway; the lines between the slab are from the epoxy resin used to piece the pieces back together.
Toward the end of the trackway, however, the horseshoe crab begins to show signs of asphyxiation from the lagoon's anoxic (no oxygen) conditions. "[T]he telson drag marks and imprints become less uniform and more erratic," they write. "[T]his may show evidence the limulid has become distressed and disorientated due to the toxic environment of the lagoon as it tries to escape."
The last section of the trackway reveals the juvenile horseshoe crab's erratic movements just before it succumbs to the anoxic and hyper-saline conditions of the lagoon. Note the uneven and discontinuous telson drag marks, which stop as the crab changes direction, indicating the strong indentations of its legs. Marks made by the animal's genial spines at the back of its body can also be seen.
