Sigmocheir furcata is a species of millipede in the family Xystodesmidae. The species is endemic to California and found in the foothills of the Sierra Nevada mountains.
Sigmocheir furcata was described by Rowland M. Shelley in 1995 based on samples collected by R. E. Graham from Williams cave in Calaveras County in 1963. As with other members of the genus, S. furcata has a distinctive trimaculate pattern with an ovoid mid-tergite yellow spot and yellow paranota. Compared to other members of the genus, the paranota on S. furcata arise slightly lower on the tergites, giving the millipedes a slightly more domed appearance. The species has light colored/white legs and antennae, and the antennae are rather long, reaching back to the third tergite.
Sigmocheir furcata is from the family Xystodesmidae (a group of often brightly patterned millipedes), within the tribe Sigmocheirini. The species was formally described as part of a revision of Sierra Nevada millipedes. Within its genus, Sigmocheir furcata is closely related to Sigmocheir calaveras and Sigmocheir maculifer, indicating Sigmocheir furcata is part of a northern lineage within the genus.
This species is the northernmost representative of the genus, being found in the foothills of the Sierra Nevada mountains to the north and southeast of Sacramento. Individuals of the genus have been found in Placer, El Dorado, Amador, Calaveras, and Sacramento counties.
Sigmocheir furcata typically occurs in foothill woodlands, moist leaf litter environments, and subterranean habitats. These habitats provide high humidity and protection from extreme temperatures. Like other millipedes, Sigmocheir furcata functions as a detritivore (decomposer), feeding on decaying plant matter and organic debris, contributing to nutrient cycling, soil formation, and fertility.