Docofossor

Docofossor is an extinct mammaliaform (a docodont) from the Jurassic period. Its remains have been recovered in China from 160 million years old rocks. It appears to have been the earliest-known subterranean mammaliaform, with adaptations remarkably similar to the modern Chrysochloridae, the golden moles.

The fossil of Docofossor brachydactylus, holotype BMNH 131735, along with that of Agilodocodon scansorius, was originally found by farmers near Nanshimen in the province of Hebei in a layer of the Chinese Tiaojishan Formation (Oxfordian) and acquired by the Beijing Museum of Natural History. The holotype consists of a compressed skeleton with skull and lower jaws, preserved on a plate and counterplate, along with soft-tissue remnants. The shoulder girdle area and the tail have been damaged. The type species Docofossor brachydactylus was named and described by Luo Zhexi, Meng Qingjin, Ji Qiang, Liu Di, Zhang Yuguang, and April I. Neander in the journal Science in 2015. The generic name refers to the membership of the Docodonta and a burrowing lifestyle, fossor meaning "digger" in Latin. The specific name is derived from Greek βραχύς, "short", and δάκτυλος, "finger", referring to the reduction of the finger phalanges.

Docofossor was at least nine centimetres long, exempting the tail, and weighed at least nine grams, perhaps sixteen. It had a skeletal structure and body proportions strikingly similar to the modern day African golden mole. It had shovel-like fingers for digging, short and wide upper molars typical of mammals that forage underground, and a sprawling posture indicative of subterranean movement. The sprawling is proven by a short hindlimb of just twenty-three millimetres, a massive olecranon as an adaptation for digging and a projecting parafibula forcing the knee joint into a bent position. Its snout point was blunt and slightly overhanging.