Phylogenetic relationships among nassariine gastropods: Combining morphologic and stratigraphic data

Phylogenetic analyses of nassariine gastropods strongly supported the monophyly of the subfamily. However, the monophyly of the Nassariidae, as it is presently defined, was not. Analyses using extant taxa placed the buccinid subfamily Photinae as sister group to the Nassariinae. Relationships between fossil buccinoids and extant lineages were not well resolved with a few exceptions. A close relationship between the Paleogene Photine Buccitriton texanum and the Nassariinae was indicated on all MPTs in the combined analysis further supporting a nassariine - photine clade.; A deeply-nested subclade of largely Indo-West Pacific (IWP) taxa represents nearly two-thirds of extant nassariine species diversity. The subclade is united the presence of a radular accessory lateral plate. Members of this subclade are typically better armored than congenerics from the East Pacific or Atlantic. Characters such as labral spines, columellar spurs, and highly developed columellar calluses are absent from or are poorly developed in non-IWP nassariines. An analysis of the IWP nassariine fossil record suggests that these features appeared relatively late in the history of the clade and are not directly related to the clade's origin during the early to middle Miocene.; The stratigraphic fit of the MPTs was measured using five common measures (RC, SCI, RCI, MSM, and stratocladistics). There was considerable agreement among stratigraphic indices reflecting the similarities in how each calculates stratigraphic fit. Trees supporting a dorsanine nassariine clade exhibited better stratigraphic fit than trees supporting a photine - nassariine clade, regardless of stratigraphic measure choice. The poor stratigraphic fit of trees supporting a photine-nassariine clade is largely the result of the relatively derived position of one fossil taxon (Buccinopsis). MSM analyses suggest that the stratigraphic fit of trees with a dorsanine-nassariine clade is not statistically significant, while the fit of trees supporting the photines as the nassariine sister group is significant. Stratocladistic, globally (stratigraphy plus morphology) MPTs also support the photines as sister group to the nassariines. Allowing stratigraphy an active role in determining tree topology (e.g., stratocladistics) or conducting statistical tests can yield different results than using amount of stratigraphic fit as a means to compare among MPTs.