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.
Their dentition became increasingly complex, and both therocephalians and cynodonts eventually developed a complete bony secondary palate (Kemp 1982).
Of all therapsids, the cynodonts acquired the most mammalian features, and the most advanced cynodonts ultimately gave rise to the first mammals (Hopson and Barghusen 1986; Rowe 1988).
However, in several cynodonts, ridges occur in the anterolateral portion of the nasal cavity, which have not been described previously.
The nasoturbinal ridges in Massetognathus are largely similar to those in other cynodonts.
The presence of respiratory turbinals in these cynodonts thus provides compelling evidence that their ventilation rates were elevated significantly above "reptilian" rates and may perhaps have approached the "mammalian" level.
Ridges probably associated with respiratory turbinals first appear among advanced therapsids, the therocephalians and cynodonts.
However, the maxilloturbinal ridges in therocephalians and cynodonts suggest that ventilation rates in these taxa had increased substantially.
If early therocephalians possessed only moderately elevated ventilation rates, the same was likely also true for the first cynodonts.
Ultimately, cynodonts gave rise to the first mammals by the end of the Triassic Period (approximately 215 million yr ago).
2011) argued for strong provinciality in the moist equatorial Pangaean region; there, traversodontid cynodonts are abundant, whereas remains of these therapsids are rare or absent and procolophonid reptiles are abundant in the Northern Hemisphere subtropics (as, for example, in the Evangeline Member of the Wolfville Formation).
Late Triassic traversodont cynodonts from Nova Scotia and southern Africa.