Long used in medical investigation, computer tomography is a new technique in palaeontology. The strength of this non-destructive visualisation method lies in the exact threedimensional x-rays which can be further processed on the computer. As the visualisation is made of voxels (= three dimensional pixels) with known volume and side-length, it is possible to measure exact length, face or volume of an abstract body. These advantages enable this study to present a picture of the nearly inaccessible cranial cavities of hyaenid skulls. The main interest was centered on the sinal cavities which represent a special skull trait in hyaenine hyaenids compared to other carnivores. Through use of computer tomography volume data could be acquired about the endocranial and the sinal cavities of the analysed specimens. The special feature of these sinal cavities are
their enormous size which is rare in carnivores.
This study tries to find coherences between sinal cavities, cranial capacity and skull size, as well as the verification or negation of the theoretical sinal cavitiy size difference in recent and extinct hyaenids. Until now the proposed size of sinal cavities in fossil cave hyenas was believed to be much larger than in recent hyenas. This was in connection with ecological differences and behaviour.
The analysis of fossil and recent hyaenid specimens however shows clearly that there is no typical difference in sinus-size which can be used for taxonomic reasons. The size differences are so undifferentiated, that no coherence can be found. On the other hand, cranial capacity (and thus brain size) shows a typical behaviour in expanding with growing skull size.