Unranked clade (stem group priapulids)
Scolecofurca belongs to the priapulid worm stem group (Harvey et al., 2010; Wills, 1998).
Scolecofurca – from the Greek skolex, meaning “worm,” and the Latin furca, “fork,” in reference to the fork-like anterior of this worm.
rara – from the Latin rarus, “infrequent,” in reference to the rarity of the species.
Holotype – GSC45331 in the Geological Survey of Canada, Ottawa, Canada.
Burgess Shale and vicinity: none.
Other deposits: none.
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
The Raymond Quarry on Fossil Ridge.
Brief history of research:
This worm was described by Conway Morris in 1977 as a possible primitive priapulid. Later analyses showed that S. rara belongs to the priapulid stem group (Harvey et al., 2010; Wills, 1998).
Scolecofurca is known from a single incomplete specimen, which is estimated to have reached nine centimeters in total length. Like other priapulids, the body is divided into a proboscis and a trunk. The proboscis is fringed with small extensions called papillae, and tipped with a pair of conspicuous tentacles giving the appearance of a two-pronged fork. The trunk is annulated and the gut appears to be represented by a simple tube. Contrary to all the other species of priapulids from the Burgess Shale, this form does not have spines or hooks on the proboscis or body.
This species is known from a single specimen.
The general body-shape and presence of a proboscis suggests Scolecofurca was a burrower. The tentacles might have had a sensory function rather than being used for prey manipulation, but the mode of feeding of this species is unknown.