Editing Therapsida (section)

===Integument===

The evolution of integument in therapsids is poorly known, and there are few fossils that provide direct evidence for the presence or absence of fur. The most basal synapsids with unambiguous direct evidence of fur are [[docodonts]], which are mammaliaforms very closely related to crown-group mammals. Two "mummified" juvenile specimens of the dicynodont ''[[Lystrosaurus murrayi]]'' preserve skin impressions; the skin is hairless, leathery, and dimpled, somewhat comparable to elephant skin.<ref>{{Cite journal |last1=Smith |first1=Roger M.H. |last2=Botha |first2=Jennifer |last3=Viglietti |first3=Pia A. |date=15 October 2022 |title=Taphonomy of drought afflicted tetrapods in the Early Triassic Karoo Basin, South Africa |url=https://linkinghub.elsevier.com/retrieve/pii/S0031018222003777 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=604 |pages=111207 |doi=10.1016/j.palaeo.2022.111207|bibcode=2022PPP...60411207S |url-access=subscription }}</ref><ref>{{Cite web |last=Timmons |first=Jeanne |date=2022-09-20 |title=These Fossil Mummies Reveal a Brutal World Long Before T. Rex Lived |url=https://gizmodo.com/these-fossil-mummies-reveal-a-brutal-world-long-before-1849558556 |access-date=2024-07-25 |website=Gizmodo |language=en-US}}</ref> Fossilized facial skin from the dinocephalian ''[[Estemmenosuchus]]'' has been described as showing that the skin was glandular and lacked both scales and hair.<ref name=Chudinov1968/>

[[Coprolite]]s containing what appear to be hairs have been found from the [[Late Permian]].<ref name=Smith2011/><ref name=Bajdek2016/> Though the source of these hairs is not known with certainty, they may suggest that hair was present in at least some Permian therapsids.

The closure of the pineal foramen in probainognathian cynodonts may indicate a mutation in the regulatory gene Msx2, which is involved in both the closure of the skull roof and the maintenance of hair follicles in mice.<ref name=Benoit2016A/> This suggests that hair may have first evolved in probainognathians, though it does not entirely rule out an earlier origin of fur.<ref name=Benoit2016A/>

Whiskers probably evolved in probainognathian cynodonts.<ref name=Benoit2016A/><ref name=Benoit2020/> Some studies had inferred an earlier origin for whiskers based on the presence of foramina on the snout of therocephalians and early cynodonts, but the arrangement of foramina in these taxa actually closely resembles lizards,<ref name=Estes1961/> which would make the presence of mammal-like whiskers unlikely.<ref name=Benoit2020/>