This fine example is a member of the genus Leanchoilia. Several
were figured in the article by Briggs and Robison as being similar
to Leanchoilia superlata from the Burgess Shale. Like those examples,
the great appendages are not preserved, but all the other diagnostic
features are present. Briggs and Robison believed it to be a new
species, which to my knowledge has yet to be described. Whatever
the precise taxonomic status, this is a most unusual and highly
desirable specimen, and the FIRST I have seen with such detail.
House Range of Utah has several formations that exhibit Burgess
Shale-like preservation of soft tissues, and yield fossils of creatures
closely allied with the Burgess Shale biota. Interestingly, the
formations are normally found in alternating biofacies. Some are
rich in trilobites lacking soft bodied organisms, while adjacent
ones lack trilobites but preserve soft bodied organisms in the form
of kerogenized carbon films. Gaines (2004) has studied the taphonomy
of House Range soft tissue preservation, hypothesizing a taphonomic
pathway much like the Burgess Shale with delayed decay facilitating
rapid diagenesis in an anoxic zone lacking benthic bioturbators.
While soft bodied organisms are far rarer and generally not so exquisitely
preserved as in the Burgess Shale, some scientists believe the House
Range biota might be even more diverse. Many fossils found are enigmatic
as to their taxonomic placement. Unfortunately, the numerous sites
are much understudied, while mining operations are resulting in
wholesale destruction of a potentially rich portion of the Cambrian
D.E.G., and R.A. Robison. 1984. Exceptionally preserved non trilobite
arthropods and Anomalocaris from the Middle Cambrian of Utah.
University of Kansas Paleontological Contributions, Paper 111:1-24.
Robert R.; Kennedy, Martin J. Droser, Mary L. 2004. A new hypothesis
for organic preservation of Burgess Shale taxa in the middle Cambrian
Wheeler Formation, House Range, Utah. Palaeo, 220:193-205.
Range Fossils: Wheeler Shale, Marjum Formation, and Weeks Formation,
The Virtual Fossil Museum (www.fossilmuseum.net).