The job of the pivot table is to summarize your source data table based on the criteria you specify in the filter fields (Report Filter, Column Labels, and Row Labels). You can think of it as a very advanced way to arrange and filter your data.
The Limulidae are the only recent family of the order Xiphosura, and contain all four living species of horseshoe crabs: 1  Carcinoscorpius rotundicauda, the mangrove horseshoe crab, found in Southeast Asia. 2  Limulus polyphemus, the Atlantic horseshoe crab, found along the American Atlantic coast and in the Gulf of Mexico.
Horseshoe crabs are often called living fossils because fossils of their ancestors date back almost 450 million years--that's 200 million years before dinosaurs existed. Despite inhabiting the planet for so long, horseshoe crab body forms have changed very little over all of those years.ncestors of horseshoe crabs date back over 450 million years--long before the age of the dinosaurs. Four species of horseshoe crabs exist today.