On the so‐called cavum orbitonasale

Abstract

AbstractBjerring, H. C. 2000. On the so‐called cavum orbitonasale. —Acta Zoologica (Stockholm) 81: 167–175Defined in the bowfin, Amia calva, the cavitas orbitonasalis (formerly the cavum orbitonasale) lies within the posteromesial part of the ethmoidal region of the endocranium and communicates with the fossa sacci nasalis and the orbita of its own side as well as with the cavitas encephalica endocranii. This intracranial compartment is probably called in being as a result of the pushing forward from the orbita of the points of origin of the ipsilateral oblique eye muscles. Its alleged presence in lizards as a part of the orbita and in mammals as a part of the cavitas encephalica cranii is shown to rest on false premizes. In reality, these two component parts are not homologous, and of all the craniate animals, extant and extinct, some actinopterygian fish alone have cavitates orbitonasales.