Morphometric analysis of the Late Cretaceous Placenticeras of Alabama, USA: Sexual dimorphism, allometry, and implications for taxonomy

A traditional typological approach to taxonomy often does not adequately account for intraspecific variation and can result in taxonomic oversplitting. For many groups, including ammonoids of the Placenticeras genus, intraspecific variation documented in recent studies (e.g., ontogenetic changes, sexual dimorphism, polymorphism) challenges the historic proliferation of species names. Here, we used a population approach to taxonomy and quantitatively evaluated morphometric variation in a sample of Late Cretaceous (Santonian -Campanian) Placenticeras from Alabama and adjacent counties.
We used linear mixed models (LMMs) to characterize how morphological variables scale with conch size across the sample, exploiting mixed longitudinal data to evaluate individual variation in growth and inform interpretations of multivariate analyses. Extended LMMs incorporating geological formation evaluated morphological changes through time. Principal component analysis and clustering analysis were then u..., Morphometric measurements were collected with digital calipers. See associated manuscript for details., , # Morphometric analysis of the Late Cretaceous *Placenticeras* of Alabama, USA: Sexual dimorphism, allometry, and implications for taxonomy

Supplemental Information accompanying the article:
\"Morphometric analysis of the Late Cretaceous *Placenticeras* of Alabama, USA: sexual dimorphism, allometry, and implications for taxonomy\"

Authors:
Rachel C. Mohr
Thomas S. Tobin
Emily M. Tompkins

## Description of the data and file structure

##### \"MOHR\_et\_al Supplement Text.pdf\"

Includes:
Supplement Text
Supplementary Tables 1-8
Supplementary Figures 1-25

##### \"MOHR\_et\_al Supplementary Data.xlsx\"

Sheet 1: \"Metadata\": overview of contents, metadata about all variables
Sheet 2: \"Specimen Information\": basic information about Placenticeras specimens (accession numbers, previous taxonomic identifications, locality information, etc.)
Sheet 3: \"Morphometric Data\": morphometric data collected from n=112 Placenticeras specimens
Sheet 4: \"main PCA (n=105)\": data included in the main PCA and ...