Helical burrow casts of therapsid origin from the Beaufort Group (Permian) of South Africa

摘要: Abstract Large helical burrow casts of vertebrate origin have been discovered at several localities in the lowermost strata Teekloof Formation Beaufort Group (Permian) southwestern Karoo basin, South Africa. They are not only oldest but also first burrows geometry to be found rocks pre-mammalian age. The vertically disposed spiralling tubes filled with fine-grained sandstone or siltstone often a calcareous cement. Tube diameters gradually increase from 60 mm upper entrance decline, through two non-contacting dextral coils, about 160 base spiral whereupon tube straightens and widens into horizontal terminal chamber. Burrow depths range 0.5-0.75 m ramp angle ranges 10 32° although within any single it is constant. Articulated skeletons small dicynodont Diictodon chambers spirals three sand-filled burrows. Linear ridges preserved on outer walls floor some resemble scratch marks possibly made by claws “beak” during excavation. sedimentary sequences separate interpreted as having deposited episodic sheet floods distributary splay-fans proximal floodbasin areas flanking an aggrading meanderbelt rise. Comparison drawn between Lower other recorded occurrences, particular, Daimonelix , beaver Miocene Nebraska. Fundamental similarities far outweigh differences extent that may grouped “daimonelices”. It concluded excavation large burrows, activity usually attributed rodents, was pre-empted mammal-like reptiles 50 million years before “anatomical mammals” evolved.