Variable morphological features in Acamptonectes densus.

The features listed here are those not previously assigned to ontogeny: typical ontogenetic features (such as sandpaper-like texture on the humerus, the shape of the capitulum of the humerus, and the overall ‘fit’ of the basicranium and forefin bones) are discussed in the text. Potentially, the variations listed here could be interpreted as representing ontogenetic, phyletic, or intraspecific variation, given the differences in ontogenetic stage (subadult VS adult) and stratigraphic age (late Hauterivian VS basal Hauterivian) of the two specimens. Because we interpret both individuals as representatives of the same species, we propose that the morphological features listed here are within normal intraspecific variation and hence possibly of limited phylogenetic interest.