Craniometric variation of some Mediterranean and Atlantic populations of Stenella coeruleoalba (Mammalia, Delphinidae): A three‐dimensional geometric morphometric analysis

Abstract

The variability of cranial features of Atlantic and Mediterranean samples of Stenella coeruleoalba was examined using a three‐dimensional geometric morphometric approach. Data were collected on 79 skulls from the upper and middle Mediterranean Sea, the Atlantic French coasts, and Scotland. Three‐dimensional x, y, and z coordinates of 27 landmarks were recorded on each left half skull using a Microscribe 3‐D digitizer. All configurations were rotated, centered, and scaled, and residuals from the mean configuration were analyzed through multivariate analyses of variance. Mahalanobis distances among populations were used to evaluate phenetic relationships. Consensus configurations were compared to visualize shape differences among samples. Analyses revealed significant differences among populations, a clear distinction of the Scottish coasts dolphins from the other samples, and a closer relationship of the dolphins from the French coasts to the Mediterranean populations than to the Scottish one. Shape differences are mainly concentrated in the rostral and in the occipital regions of the skull. Phylogenetic and adaptive factors were invoked as possible causes of the variation patterns.

Ontogenetic development and sexual dimorphism of franciscana dolphin skull: A 3D geometric morphometric approach

“…Although the longer rostrum suggests a decreasing of the mechanical advantages at the tip (Preuschoft and Witzel, ; Segura and Prevosti, ; Segura et al, ), its length, associated with a well‐developed temporal musculature, also implies a gain in mouth‐closing speed at the tip, making prey catch function in adults more efficient. These observations are in agreement with those by Loy et al (), who suggested that the elongation of the rostrum might be related to differences in feeding habits for different populations on Stenella coeruleoalba .…”

Timing of ontogenetic changes of two cranial regions in Sotalia guianensis (Delphinidae)

“…Some morphological aspect described here and by those authors, namely the downward inflexion of the rostrum and the ventral displacement of the foramen magnum seems to be common not only to ontogenetic trends, but also for between (Galatius 2010) and within species variation (Loy et al 2010). While these aspects are suggested to be related to foraging in shallow waters (Monteiro-Filho et al 2002), forms with the rostrum more aligned with the vertebral column, such as the ones associated with older individuals here, are though to be related do pelagic feeding (Galatius 2010;Loy et al 2010). The reoccurrence of these morphological patterns within Delphinidae, its correlation with ontogenetic trends and its apparent correlation with different aquatic habitats, suggests that there might be an underling genetic and developmental phenomenon that could facilitate adaptation to different environments (Schluter 1996).…”

Three‐dimensional surface scanning methods in osteology: A topographical and geometric morphometric comparison

“…In comparison to surface-based methods, a point MicroScribe digitizer is a quick and cheap method to collect small to intermediate sets of landmarks (Vu et al, 2017). It has been used in various fields, including anthropology and primatology (e.g., Aung et al, 1995;Cardini & Elton, 2008;Mehta & Marinescu, 2001;Mitteroecker et al, 2004;O'Higgins & Jones, 1998;Ross & Williams, 2008;Sholts et al, 2011;Singleton, 2002;Vidarsdottir et al, 2002;Von Cramon-Taubadel et al, 2007), medicine (e.g., Chen et al, 2008;Dastane et al, 1996), and zoology (e.g., Loy et al, 2011;Milne et al, 2009;Owen et al, 2014).…”