The more derived portion of Clade N4 that constitutes Hemipilia s.s. is readily circumscribed by both sequence (especially nuclear) data and morphological synapomorphies, notably the protruding, tongue-like rostellum (though a similarly shaped rostellum characterizes the basal member of the clade, Hemipiliopsis).
In contrast, until now only few morphological synapomorphies, notably placental morphology [ 30], an increase in number of thoracolumbar vertebrae [ 31], and testicondy [ 32], appear to support this grouping.
Smerinthini, even excluding Langia and Sphingulini, are a morphologically heterogeneous group for which morphological synapomorphies are lacking.
There are groups of species e.g. from Microlepidoptera, Pyralidae, that are far more difficult to assign morphologically to taxa and lack of morphological synapomorphies may reflect the instability of the current classification.
It is likely that some so-called morphological synapomorphies in traditional systematics are in fact morphological similarities as a result of convergent evolution.
The resolution of notothenioids within "trachinoids" in a previous phylogenetic analysis was potentially the result of morphological synapomorphies shared with Percophis [ 30], but relationships were likely obfuscated by scoring morphological character states for "percophids" as a single taxon that comprised the polyphyletic assemblage comprising Bembrops, Percophis and Hemerocoetes [ 31, 64].
Phylogenetic relationships within Conchifera are also far from settled due to the highly derived morphologies within each class-level grade, which hinder the discovery of morphological synapomorphies across lineages [ 17].
The lack of strong morphological synapomorphies to distinguish it from related genera in the region necessitates molecular data in ascertaining generic placements (Xu et al. 2012ab).
This is surprising for a group whose monophyly and morphological synapomorphies appear quite clearly [35].
This is because we cannot think of any morphological synapomorphies of the two groups that can be used as diagnostic features, except perhaps the fact that species allied with Pseudostomella lack cephalic tentacles, whereas cephalic tentacles, rod- and/or knob-like are present in the species that cluster with Ptychostomella.
