Enigmatic Creature #3 from Cambrian Utah (Phyllocarid?)
From a Burgess Shale-like Laggerstatt

Name: Phyllocarid?

Geological Time: Upper Middle Cambrian

Size (25.4mm=1 inch): 21 mm long by 19 mm across on a 58 mm by 56 mm matrix

Location: House Range, Weeks Formation, Millard County, Utah

Phyllocarid fossilDescription: This fine problematic creature looks something like a Phyllocarid seen from the lateral aspect. It has a reticulated pattern seen in some Tuzoia. While that is only a tentative identification, it is at least an attempt—there are many enigmatic creatures showing up in recently-discovered strata of the Middle Cambrian Weeks Formation. It is the only the second such example ever seen by the source, and would make a welcome addition to any collection of Cambrian fossils.

The 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 fossil record.


  • Briggs 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.
  • Gaines, 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.
  • House Range Fossils: Wheeler Shale, Marjum Formation, and Weeks Formation, The Virtual Fossil Museum (www.fossilmuseum.net).

click fossil pictures to enlarge

l Fossil Mall Home l Fossils Science Section l