Does skull morphology constrain bone ornamentation? A morphometric analysis in the Crocodylia

Area of Science:

• Comparative anatomy
• Phylogenetics
• Geometric morphometrics

Background:

• Dermal bone ornamentation in crocodylians (pits and ridges) creates regional differences in surface area.
• Ornamentation gain is typically higher on the skull table than the snout.

Purpose of the Study:

• To investigate if crocodylian dermal bone ornamentation depends on skull morphology (shape and size).
• To perform a comparative phylogenetic analysis across diverse crocodylian species.

Main Methods:

• Quantitative assessment of skull size and shape using geometric morphometrics.
• Surface analyses to quantify skull ornamentation.
• Phylogenetic least-squares regression to analyze the dataset.

Main Results:

• Ornamentation variables (snout and skull table) showed no correlation with specimen size.
• Snout elongation was negatively correlated with pit depth/shape (GApit) and relative pit area (OArelat).
• Skull table ornamentation showed no correlation with skull conformation.

Conclusions:

• Bone sculpture on the snout is influenced by different developmental constraints and local growth contexts than on the skull table.
• Ornamentation's functional role may be region-specific, particularly in longirostrine (elongated snout) forms which show reduced snout ornamentation.