2-454: Dekatriata is a clade of planatergan chelicerates including the groups Arachnida , Chasmataspidida , Eurypterida and additionally two stem-genera Winneshiekia and Houia . Dekatriata is defined by an opisthosoma with 13 segments as groundplan (the number proposed to be secondarily reduced in most arachnid orders) and fused, plate-like appendages on the first opisthosomal segment (somite VII). This Chelicerata -related article
4-638: Is a stub . You can help Misplaced Pages by expanding it . Planaterga Planaterga is a clade of prosomapod euchelicerates including several synziphosurid genera (mainly bunodids and pseudoniscids ) and the group Dekatriata (which in turn includes arachnids , chasmataspidids and eurypterids ). Planaterga is defined by the opisthosoma with tergites broadest at third or fourth and lacking enlarged axial nodes, carapace (prosomal dorsal shield) with reduced genal spines, as well as somite VII (first opisthosomal segment) with reduced appendages and microtergite. This Chelicerata -related article
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