However, Colgan et al. 2003 [ 34] proposed a reevaluation of the morphological characters defining Patellogastropoda and its relationships with other gastropods.
Nineteen morphological characters were defined based on the discontinuous variation of the female reproductive tract (Table 2).
The three main clades could be considered as tribes and we list some morphological characters that define them.
In all our analyses based on nuclear rDNA data, the three species of Plakinastrella form a monophyletic group, thus making the combination of those spicules a valid morphological character to define this genus.
It has, however, been used in taxonomy as the main morphological character to define several traditional genera, such as Microcoleus, Schizothrix or Hydrocoleum [3], with the tacit phylogenetic implication that rope-building is a synapomorphy, a case of shared inheritance of this trait in the present-day descendants of a common ancestor that built such ropes.
The monophyly of the rhizomatous Clade SVLB suggests a single evolutionary origin of the adaptation to the cave-like limestone microhabitats, and shows that ecology is good indicator of taxonomic relationships than traditional morphological characters used to defined sections.
Based on an analysis of how morphological characters used in defining Begonia sections evolve across a chloroplast DNA phylogeny (Thomas et al., 2011), it has become clear that Begonia sect.
Our results support previous assertions on the scarcity of clear morphological characters that would define larger assemblages of ditrysian superfamilies [ 2], and no new such characters were found.
This most probably suggests a rapid colonization of the islands followed by a strong effect of selection operating over the morphological characters used to define the subspecies.
The two groups share a number of morphological characters (synapomorphies) that define the vertebrates, such as the neurogenic placode, neural crest, and their derivatives, including complex sense organs and a cranial skeleton [ 1- 3].
