Burgess Shale-type preservation of both non-mineralizing and ‘shelly’ Cambrian organisms from the Mackenzie Mountains, northwestern Canada

• Published in: Journal of Paleontology
• Main Authors: Butterfield, N. J., Nicholas, C. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1996
• Subjects: Mackenzie mountains
• Online Access: http://dx.doi.org/10.1017/s0022336000038579; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000038579

Lower to Middle Cambrian shales of the Mount Cap Formation in the Mackenzie Mountains, northwestern Canada, host a variety of Burgess Shale-type macrofossils, including anomalocarid claws, several taxa of bivalved arthropod, articulated hyolithids, and articulated chancelloriids. Hydrofluoric acid processing has also yielded a broad range of organic-walled fossils, most of which are derived from forms more typically known as shelly fossils; e.g., trilobites, inarticulate brachiopods, small shelly fossils (SSF), hyolithids, and chancelloriids. Organic-walled hyolithids include conchs, opercula and helens; the proximal articulation of the helens is erosive, suggesting that they were formed “instantaneously” and periodically replaced. Organic-walled chancelloriid sclerites exhibit a polygonal surface texture and an inner “pith” of dark granular material with distally oriented conoidal divisions; such a pattern is similar to that seen in the fibers of some modern horny sponges and points to a poriferan relationship for the chancelloriids. The robust nature but minimal relief of most of these fossils suggests that primary biomineralization was minimal.