Nevertheless, at this time not enough is known about the effect of strong air currents on olfactory epithelium to support a close, functional association between these turbinals and endothermy.
Avian turbinals probably have respiratory and olfactory functions analogous to those of mammals.
The locations of these basal ridges reflect the functions of the turbinals as well.
Like the turbinals of the prefrontals, however, these would have been primarily olfactory in function.
The many olfactory turbinals in gorgonopsians suggest that these animals had a comparatively well-developed olfactory sense but says little about their ventilation rates.
Additional ridges, which most likely supported olfactory turbinals, are present elsewhere in the nasal cavity of Glanosuchus.
It is not known at present whether other therocephalians possessed respiratory turbinals. However, the nasal respiratory chamber of therocephalians gradually expanded during their evolution, as indicated by the progressive posterior migration of the internal nares.
Respiratory turbinals are found only in mammals and birds, and their function, at least in mammals, but probably in birds as well, is to reduce the respiratory water losses associated with rapid and continuous pulmonary ventilation, a fundamental component of endothermic physiology (Hillenius 1992).
In addition, the respiratory turbinals of mammals are closely associated with the ostium of the nasolacrimal duct.
Examination of the nasal cavities of the ancestors of mammals, the synapsid reptiles, indicates that olfactory turbinals were very likely present at an early stage, among the earliest forms to diverge from the main reptilian ("sauropsid") lineage, and well before endothermy was likely to have evolved.
Ridges probably associated with respiratory turbinals first appear among advanced therapsids, the therocephalians and cynodonts.
In this form, respiratory turbinals occur together with an essentially reptilian palatal configuration, which limits the nasal respiratory chamber, and most likely its capacity to modify respiratory air.