Although in adult mammals this turbinal is generally attached to the maxillary bone, rather than the nasal, it develops ontogenetically from a distinct cartilaginous precursor, which only later becomes attached to the adjacent dermal bones (Moore 1981).
The presence of possible respiratory turbinal ridges in Glanosuchus suggests that its nasal cavity had become actively involved in the conditioning of respired air, and suggests that the ventilation rate of this animal had increased enough to result in significant respiratory water loss.
Longitudinal turbinal ridges have long been noted on the inner surfaces of the nasal, frontal, and prefrontal bones of many cynodonts [Procynosuchus, Kemp 1979; Thrinaxodon (including "Nythosaurus"), Watson 1913; Fourie 1974; Diademodon, Watson 1913; Brink 1955, 1956; Exaeretodon, Bonaparte 1966; Luangwa, Kemp 1980; Oligokyphus, Kuhne 1956].
These ridges correspond in location to the maxilloturbinal ridges of extant mammals and are similar to the ridge for the respiratory turbinal of Glanosuchus, described above.
Their location in the large respiratory chamber, and their association with the nasolacrimal duct strongly suggest that these ridges supported a turbinal structure like that found in extant mammals, with a similar water-recovery function.
The pattern of nasal turbinal ridges in therapsids indicates that the ventilation rates of the more primitive groups (dinocephalians, dicynodonts, and gorgonopsians) probably had not yet increased significantly beyond ancestral rates.
The nasal turbinal ridges of the earliest mammals are essentially identical to those of extant mammals, suggesting that the development of "mammalian" respiration rates and endothermy was largely complete by this time (cf.
Heretofore, no evidence for the existence of strictly respiratory turbinals has been described for mammallike reptiles, although they are known in early mammals (e.g., Kermack et al.
Several newly prepared fossil specimens are described, which suggest that respiratory turbinals did, in fact, occur among therocephalians and cynodonts, two groups of advanced therapsids.
The anterior and middle turbinals of birds are situated in the respiratory passage and are covered primarily with mucociliated respiratory epithelium (Bang and Bang 1959; Parsons 1971).
Embryonically, the conchae and turbinals of all higher tetrapods develop from folds of the cartilaginous nasal capsules (Goodrich 1930; Matthes 1934; Parsons 1970; Moore 1981).
The respiratory turbinals of birds also appear capable of reducing respiratory water loss (Schmidt-Nielsen et al.