However, the turbinates most frequently cited with reference to endothermy in therapsids have been ethmoturbinals (e.g., Watson 1913; Brink 1956; Van Valen 1960; Bennett and Ruben 1986).
Posteriorly, numerous ethmoturbinals typically fill the olfactory portion of the nasal cavity.
It is often considered one of the ethmoturbinals (e.g., Allen 1882; Paulli 1900a,b,c; Allison 1953; Moore 1981), as at least part of it appears to have the same embryonic origin as the latter.
The ethmoturbinals, alternately, are incapable of modifying the water content of large volumes of air.
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.
As mentioned above, the nasoturbinal is often considered one of the ethmoturbinals; it may have extended forward to allow air samples to bypass the maxilloturbinal.
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.
The arrangement of these ridges closely resembles the typical pattern in modern mammals and indicates that both respiratory and olfactory turbinates (i.e., maxilloturbinals, and naso- and ethmoturbinals) were present.
Remnants of maxilloturbinals and ethmoturbinals, which indicate that these structures were quite extensive and complex, are described in several specimens.