|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||Age range and collections|
Xiphosura - Xiphosurida
If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
|J. C. Lamsdell 2013||Prosomapoda lacking enlarged axial nodes on opisthosomal tergites; genal spines vestigial; opisthosoma broadest at third or fourth tergite; appendages of somite VII reduced; tergite of somite VII beginning to form microtergite.|