OPISTHOSOMAL FUSION AND PHYLOGENY OF PALEOZOIC XIPHOSURA

Fusion of opisthosomal tergites to form a thoracetron has previously b een considered a characteristic of the xiphosuran superfamilies Euproo poidea Eller, 1938, and Limuloidea Zittel, 1885. Evidence is presented here that fusion also occurs in Bellinuroidea Zittel & Eastman, 1913. Results of a cladistic analysis of Palaeozoic xiphosuran genera indic ate that Synziphosurina Packard, 1886, is a paraphyletic assemblage of stem-group Xiphosura. Superfamily Paleolimulidae superfam. nov. is er ected for families Paleolimulidae Raymond, 1944, and Moravuridae Priby l, 1967.