 This makes "P. newmani" the earliest documented arthropod with a tracheal system, and indeed the first known oxygen-breathing animal on land.Trace fossils of myriapods are known dating back to the late Ordovician (the geologic period preceding the Silurian), but "P. newmani" is the earliest body fossil of a millipede, and has been dated to (late Wenlock epoch to early Ludlow epoch).The earliest centipedes follow some 10 million years later, and the first known vertebrate on land, "Tiktaalik", is 50 million years younger than "Pneumodesmus".