Belongs within: Euchelicerata. The Trigonotarbida are a group of fossil arachnids known from the late Silurian to early Permian (Dunlop & Selden 2004). Characters (from Dunlop & Selden 2004): Opisthosoma with nine dorsal tergites divided into median and lateral plates; tergites 2 and 3 commonly fused into single macrotergite; two pairs of book-lungs present. <==Trigonotarbida… Continue reading Trigonotarbida