Staurozoan classification is highly subjective, based on phylogeny-free inferences,
and suborders, families, and genera are commonly defined by homoplasies.
Additionally, many characters used in the taxonomy of the group have ontogenetic
and intraspecific variation, and demand new and consistent assessments to
establish their correct homologies. Consequently, Staurozoa is in need of a
thorough systematic revision. The aim of this study is to propose a comprehensive
phylogenetic hypothesis for Staurozoa, providing the first phylogenetic
classification for the group. According to our working hypothesis based on a
combined set of molecular data (mitochondrial markers COI and 16S, and nuclear
markers ITS, 18S, and 28S), the traditional suborders Cleistocarpida (animals
with claustrum) and Eleutherocarpida (animals without claustrum) are not
monophyletic. Instead, our results show that staurozoans are divided into two
groups, herein named Amyostaurida and Myostaurida, which can be distinguished
by the absence/presence of interradial longitudinal muscles in the peduncle,
respectively. We propose a taxonomic revision at the family and genus levels that
preserves the monophyly of taxa. We provide a key for staurozoan genera and
discuss the evolution of the main characters used in staurozoan taxonomy.
