|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Xiphosura - Sessilia - Scalpellidae
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.
|R. M. Finks 1960||Spheroidal; spicule layers concentric and parallel to whole surface; one or several circular oscules; ostia mostly confined to one or more restricted fields; surface canals anastomose over most of surface except for ostial fields.|