Data from: Evolutionary adaptation to aquatic lifestyle in extinct sloths can lead to systemic alteration of bone structure

Through phenotypic plasticity, bones can change in structure and
morphology, in response to physiological and biomechanical influences over
the course of individual life. Changes in bones also occur in evolution as
functional adaptations to environment. In this study, we report on the
evolution of bone mass increase (BMI) that occurred in the postcranium and
skull of extinct aquatic sloths. Although non-pathological BMI in
postcranial skeleton has been known in aquatic mammals, we here document
general BMI in the skull for the first time. We present evidence of
thickening of the nasal turbinates, nasal septum, and cribriform plate,
and further thickening of the frontals, and infilling of sinus spaces by
compact bone in the late and more aquatic species of the extinct sloth
Thalassocnus. Systemic bone mass increase occurred among the successively
more aquatic species of Thalassocnus, as an evolutionary adaptation to the
lineage’s changing environment. The newly documented pachyostotic
turbinates appear to have conferred little or no functional advantage and
are herein hypothesized as a correlation with or consequence of the
systemic BMI among Thalassocnus species. This could in turn be consistent
with a genetic accommodation of a physiological adjustment to a change of
environment.