The unreliability of the first and last observed instances of these objects is explained through the Signor–Lipps effect. Ichnologists (“ick-NOL-uh-jists”) study so-called “trace” examples of these objects, which provide the primary evidence for the substrate revolution. The relative ordering of these objects are considered when invoking the law of faunal succession. Stratigraphic correlation may be performed using easily identifiable (-5[1])examples of these objects with short temporal range and wide geographic distribution. Lagerstätten of these objects include the Burgess Shale and La Brea Tar Pits. For 10 points, graptolites and brachiopods are examples of the “index” type of what preserved remains of past organisms? ■END■ (10[1])