Data from: Geometric morphometric character suites as phylogenetic data: extracting phylogenetic signal from gastropod shells

Despite being the objects of numerous macroevolutionary studies, many of
the best-represented constituents of the fossil record—including diverse
examples such as foraminifera, brachiopods, and mollusks—have mineralized
skeletons with limited discrete characteristics, making morphological
phylogenies difficult to construct. In contrast to their paucity of
phylogenetic characters, the mineralized structures (tests and shells) of
these fossil groups frequently have distinctive shapes that have long
proved useful for their classification. The recent introduction of
methodologies for including continuous data directly in a phylogenetic
analysis has increased the number of available characters, making it
possible to produce phylogenies based in whole or part on continuous
character data collected from such taxa. Geometric morphometric methods
provide tools for accurately characterizing shape variation and can
produce quantitative data that can therefore now be included in a
phylogenetic matrix in a non-arbitrary manner. Here, the marine gastropod
genus Conus is used to evaluate the ability of continuous
characters—generated from a geometric morphometric analysis of shell
shape—to contribute to a total evidence phylogenetic hypothesis
constructed using molecular and morphological data. Furthermore, the
ability of continuous characters derived from geometric morphometric
analyses to place fossil taxa with limited discrete characters into a
phylogeny with their extant relatives was tested by simulating the
inclusion of fossil taxa. This was done by removing the molecular
partition of individual extant species to produce a “cladistic
pseudofossil” with only the geometric morphometric derived characters
coded. The phylogenetic position of each cladistic pseudofossil taxon was
then compared with its placement in the total evidence tree and a
symmetric resampling tree to evaluate the degree to which morphometric
characters alone can correctly place simulated fossil species. In 33-45%
of the test cases (depending upon the approach used for measuring
success), it was possible to place the pseudofossil taxon into the correct
regions of the phylogeny using only the morphometric characters. This
suggests that the incorporation of extinct Conus taxa into phylogenetic
hypotheses will be possible, permitting a wide range of macroevolutionary
questions to be addressed within this genus. This methodology also has
potential to contribute to phylogenetic reconstructions for other major
components of the fossil record that lack numerous discrete characters.