Walcott (1919) considered Yuknessia as a green alga, a view shared by Conway Morris and Robison (1988). However, no revision of the type material from the Burgess Shale has been published since its original description and its affinities remain uncertain.
Yuknessia – from Yukness Mountain (2,847m), a Peak in Yoho National Park, east of the Burgess Shale.
simplex – from the Latin simplex, meaning “simple,” in reference to the simple morphology of this alga.
Holotype – USNM 35406 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Burgess Shale and vicinity: none
Other deposits: Yuknessia sp. from the Lower Cambrian Niutitan Formation in China (Yang et al., 2003).
Middle Cambrian, Bathyuriscus-Elrathina Zone to Ptychagnostus punctuosus Zone (approximately 505 million years ago).
Burgess Shale and vicinity: The Walcott Quarry on Fossil Ridge and the Trilobite Beds on Mount Stephen.
Other deposits: Y. simplex is known from the Middle Cambrian Spence Shale and the Marjum and Wheeler Formations in Utah (Conway Morris and Robison, 1988).
Brief history of research:
This genus was described by Charles Walcott (1919) as a possible green alga. However, like all the algae from the Burgess Shale, it awaits a modern redescription (see Dalyia). Conway Morris and Robison (1988) described specimens of this species from several Utah deposits.
This alga has long branches emerging from a short but wide hollow stem covered of small conical elements or plates. The plates were the attachment sites of the branches. The branches show strong similarities with Dalyia and suggest the two species might be synonymous, with Yuknessia representing the main stem structure of the Dalyia branches.
Yuknessia is very rare and represents only 0.04% of the Walcott Quarry community (Caron and Jackson, 2008).
The wide stem suggests this species was attached to the sea floor within the photic zone rather than being free floating.