TRACKING THROUGH THE CAMBRIAN

Pterocephalia norfordi, McKay Group

A lovely Pterocephalia norfordi trilobite from Upper Cambrian, Furongian strata of the McKay Group, East Kootenay Region, southeastern British Columbia, Canada. 

The McKay Group has been explored extensively these past few years by Chris New and Chris Jenkins of Cranbrook, British Columbia. 

Together, these two avid trilobite enthusiasts have opened up considerable knowledge on the exposures, collaborating with researchers Brian Chatterton and Rudy Lerosey-Aubril. They have unearthed many new specimens and several new species. 

Pterocephalia from this region are relatively common. We also find Wujiajiania lyndasmithae along with a host of other Upper Cambrian goodies. 

I collected dozens of well-preserved fully articulated specimens over the course of a week in August 2020, walking in the sacred lands of the Ktunaxa or Kukin ʔamakis First Nations. 

My eyes were good enough to find the specimens themselves, but not as refined as those of Chris Jenkins who spotted the unusual preservation of the embedded gut tract. Brian Chatterton et al. published on it in 1994 and have been following it up year upon year with paper after paper out of these localities. 

Rudy Lerosey-Aubril published a paper in 2017 on phosphatized gut remains — relatively common in this taxon at this site. Lerosey-Aubril’s paper was on an aglaspidid, a combjelly, and the gut of another trilobite. 

Skeletal remains of trilobites are abundant in Palaeozoic rock but soft parts are rarely preserved. 

There have been a few papers on trilobite gut remains from Canada and on abundant trilobite faunas of the Kaili Formation of Guizhou, China. 

The Kaili contains one of the earliest middle Cambrian Burgess Shale-type deposits, sharing many faunal elements with the older Chengjiang Biota (Chen 2004; Hou et al. 2004) and the younger Burgess Shale Biota (Briggs et al. 1994). 

The biota, facies description, and regional stratigraphy of the Kaili Biota were discussed and reviewed in Zhao et al. (2002, 2005) and Lin et al. (2005). 

Their colleagues (Zhao et al. 1994b, 1996, 1999, 2001, 2002) have beautifully illustrated many Kaili arthropods with soft-part preservation, but most of their systematic descriptions are yet complete.

References: Chatterton BD, Johanson Z, Sutherland G. 1994. Journal of Paleontology 68:294-305. 

Lin, Jih-Pai. (2007). Preservation of the gastrointestinal system in Olenoides (Trilobita) from the Kaili Biota (Cambrian) of Guizhou, China. Memoirs of the Association of Australasian Palaeontologists. 33. 179-189. 

Top Photo: This specimen was collected by Dan Bowden and photographed by the Huntress. It has been checked for the dark telltale signs of phosphatized gut remains — sadly no luck!

Middle Photo: Warm summer light atop the mountains and my temporary home-sweet-home. Bottom Photo: Upper Cambrian collecting beds beneath Tanglefoot Mountain, McKay Group, East Kootenay Region, British Columbia, Canada.