Data for: Increasing information content and diagnosability in family-level classifications

Higher-level classifications often must account for monotypic taxa
representing depauperate evolutionary lineages and lacking synapomorphies
of their better-known, well-defined sister clades. In a ranked (Linnean)
or unranked (phylogenetic) classification system, discovering such a
depauperate taxon does not necessarily invalidate the rank classification
of sister clades. Named higher taxa must be monophyletic to be
phylogenetically valid. Ranked taxa above the species level should also
maximize information content, diagnosability, and utility (e.g., in
biodiversity conservation). In spider classification, families are the
highest rank that is systematically catalogued, and incertae
sedis is not allowed. Consequently, it is important that
family-level taxa be well defined and informative. We revisit the
classification problem of Orbipurae, an unranked suprafamilial clade
containing the spider families Nephilidae, Phonognathidae, and
Araneidae sensu stricto. We argue that, to maximize
diagnosability, information content, conservation utility, and practical
taxonomic considerations, this “splitting” scheme is superior to its
recently proposed alternative, which lumps these families together as
Araneidae sensu lato. We propose to redefine Araneidae and
recognize a monogeneric spider family, Paraplectanoididae fam. nov. to
accommodate the depauperate lineage Paraplectanoides. We present
new subgenomic data to stabilize Orbipurae topology which also supports
our proposed family-level classification. Our example from spiders
demonstrates why classifications must be able to accommodate depauperate
evolutionary lineages, for example, Paraplectanoides. Finally,
although clade age should not be a criterion to determine rank, other
things being equal, comparable ages of similarly ranked taxa do benefit
comparative biology. [Classification, family rank, phylogenomics,
systematics, monophyly, spider phylogeny.]