When trilobites are found, only the exoskeleton is preserved (often in an incomplete state) in all but a handful of locations. A few locations (Lagerstätten) preserve identifiable soft body parts (legs, gills, musculature & digestive tract) and enigmatic traces of other structures (e.g. fine details of eye structure) as well as the exoskeleton.
Trilobites range in length from 1 mm to 72 cm (1/25 inch to 28 inches), with a typical size range of 3 to 10 cm (1 to 4 inches). The world's largest trilobite, Isotelus rex, was found in 1998 by Canadian scientists in Ordovician rocks on the shores of Hudson Bay.[10]