It assumed that Triarthrus eatoni had a symbiotic relationship sulfur bacteria. This probably favours the formation of pyrite so that sometimes the soft body parts like Legs and grills are preserved.
Location:
Martinsburg, New York, USA
Size trilobite:
about 12 mm long
Age:
Upper Ordovizian, late Caradoc , (about. 449 Mill. Mill. y.o.)