02.11.2010., utorak
FOSSIL SPIDERS
 The oldest spiders have been found in the sediments from the Middle Devonian period (400 million years ago) in the federal state of New York (the US). Their body was not yet segmented as in today´s spiders. Because of their thin outer skeleton, the fossil remnants of spiders are usually badly preserved. In addition to that, spiders can walk on smooth water surface without getting drowned, so we also rarely find them in fossil remnants of lake sediments. Most fossil spiders originate from America, e.g. in sediments from the Upper Carbon period in the Mazon Creek area in Illinois, US (300 million years ago), or from the Cretaceous period in Santa-Formation in Brazil (110 million years ago). Many spider fossils have remained glued in wood resin and have been preserved inside it. In the archeological site of Natural History Museum Maarmuseums Manderscheid, the crater lake Eckfelder Maar near Manderscheid in Germany (44,3 million years old), there have been mostly fossil remnants of pyritized spiders and Opiliones preserved. Pyritized is a process whereby the outer skeleton is replaced with pyrite (FeS2). |
