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.
The ethmoturbinals are supported by a series of more or less parallel ridges, usually located on the ventromedial surfaces of the frontal bone.
Remnants of maxilloturbinals and ethmoturbinals, which indicate that these structures were quite extensive and complex, are described in several specimens.
In mammals, the olfactory naso- and ethmoturbinals attach to ridges in the dorsal and posterior portions of the nasal cavity, away from the path of respired air.