These are similar to ridges observed in other therapsids and to the ridges that support the nasoturbinals of extant mammals.
Both remaining groups of therapsids, the therocephalians and the cynodonts, became increasingly mammallike in appearance during their evolution.
These ridges are similar to the nasofrontal ridges found in other therapsids and to the ridges of the mammalian nasoturbinals.
As in many other therapsids, its posterior half consists of two closely parallel ridges separated by a narrow groove.
Nevertheless, as Glanosuchus dates from the middle Late Permian, about 260 million yr ago (Van den Heever 1987), this ridge marks the earliest indication that the ventilation rates of advanced therapsids had expanded over ancestral "reptilian" rates.
Cynodonts supplanted the gorgonopsians and therocephalians as the dominant therapsids during the Early Triassic Period (Kemp 1982; Carroll 1988) and persisted throughout the Triassic and into the Jurassic.
However, these ridges do not differ from those of earlier therapsids and correspond to the ridges that support the olfactory ethmo- and nasoturbinals of extant mammals.
Similar ridges also are found throughout the therapsids, the descendants of pelycosaurs.
Ridges probably associated with respiratory turbinals first appear among advanced therapsids, the therocephalians and cynodonts.