Variation of the ferret skull (Mustela putorius furo L.) in relation to stereotaxic landmarks.

The ferret skull was investigated to identify reliable extracranial landmarks for stereotaxy. The skulls of 56 ferrets of both sexes were measured in a stereotaxic apparatus. Neither body weight nor an index of skull length proved to be reliable predictors of intracranial location. Sutures fused too early in life for lambda and bregma to be useful as landmarks in adult ferrets. The position of extracranial features was used to predict the position of intracranial features. For rostral intracranial features, the supraorbital processes were found to be the best predictors. Although the occipital crest was not the best predictor for posterior structures, it was the most practical. Using these landmarks, the prediction of intracranial location could be improved by more than 30%. Sexual dimorphism was found for all features examined except those nearest the interaural line. Female skulls were significantly smaller than male skulls and had less prominent sagittal and occipital crests. Males showed a substantial variation in the structures surrounding the pituitary gland. Fitches were also found to differ from albinos in having a more marked development of the sagittal crest.