One or two additional ridges are located posterolateral to these, in the preorbital olfactory recess, which closely resemble ethmoturbinal ridges.
These are located on the frontal and prefrontal bones, lateral to the posterior part of the nasoturbinal ridge, and correspond to the ethmoturbinal ridges of other therapsids and extant mammals.
In MCZ 4219, several ethmoturbinal ridges are present on the prefrontal and the orbital process of the lacrimal.
However, the turbinates most frequently cited with reference to endothermy in therapsids have been ethmoturbinals (e.
Posteriorly, numerous ethmoturbinals typically fill the olfactory portion of the nasal cavity.
It is often considered one of the ethmoturbinals (e.
Consequently, the space occupied by the ethmoturbinals is ordinarily not ventilated, except during deliberate "sniffing" (fig.
This implies that mammalian ethmoturbinals evolved later, after the divergence of reptiles and mammals.
Whereas the ethmoturbinals are far more complex and extensive than reptilian conchae, they retain the same sensory function.
A similar retreat of sensory epithelium is occasionally seen on the rostral tips of the ethmoturbinals, where these dip into the airstream (e.
Conversely, the mammalian ethmoturbinals retain the primitive olfactory function of the nasal conchae, although their increased complexity in mammals might be correlated to high air current velocities.