|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||Age range and collections|
Pterobranchia - Tetragrapta
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. Maletz et al. 2009||The crown-clade Tetragrapta is the common
ancestor of Tetragraptus serra and the first species to have
distal dicalycal thecae limited to th31 and th32, forming a
quadriramous rhabdosome (synapomorphy 6, Fig. 2; see
also Fig. 4B).