Middle Cambrian Hyolithids - BAS

[Arizona Chris]

Greetings all,

 

Another big project just completed, our photo survey of nearly every Hyalithid we found at our SW locality near Ashfork Arizona in the lower middle Cambrian Bright Angel shale.  Me and my wife have been working on this project for several months now, getting all the specimens cleaned, prepared and photographed.  The shale is greenish in color due to glauconite and is fine grained, preserving many of the finest details in the specimens.  This contrasts greatly to the southern extension (in Arizona) of the BAS known as the "Abrigo Formation" which leaves much to be desired for the quality of preservation.  Fortunately, the age of the BAS is about 5 MY older than the famous Burgess Shale, and many of the faunal elements are identical or very similar.  The hyolithids here are "Hyolithes sp." same as the Burgess, but lack the curved extensions known as "Helens" which normally protrude out the sides of the conchs.  In fact we looked extensively for these features, but they were not present even in the best preserved specimens.  Apparently, not all Hyolithids had them.  

 

Here are a few images from this survey, and I would encourage you to take a look at our main web page summary of this study which can be found here:

 

http://www.schursastrophotography.com/paleo/Fossilfotos-4e.html

 

Selected hyolithids images from the survey:

 

 

 

 

 

Thanks for looking, this was indeed a very illuminating project for us!  Glad to share this with all of you!

 

[ynot]

Very nice!

Thanks for sharing all of Your research!

 

Tony

[piranha]

5 hours ago, Arizona Chris said:

The hyolithids here are "Hyolithes sp." same as the Burgess...

 

 

Here is an update according to Foster 2011, they are removed from Hyolithes:

 

"Most hyolithid specimens in the Bright Angel Shale were referred to Hyolithes sp. by McKee and Resser (1945), but other genera (e.g., Haplophrentis) are now known from middle Cambrian rocks. The preservation of the Bright Angel Shale hyolithid specimens prevents more detailed identification of the material at this time."

 

Foster, J.R. (2011)
Trilobites and other fauna from two quarries in the Bright Angel Shale (Middle Cambrian, Series 3; Delamaran), Grand Canyon National Park, Arizona. pp. 99-120

In: Hollingsworth, J.S., Sundberg, F.A. & Foster, J.R. (eds) 
Cambrian Stratigraphy and Paleontology of Northern Arizona and Southern Nevada. 
Museum of Northern Arizona Bulletin, 67:1-321  LINK

 

McKee, E.D., & Resser, C.E. (1945)

Cambrian History of the Grand Canyon Region.

Carnegie Institute Publication, 563:1-232  LINK

[Arizona Chris]

Certainly these hyolithids are different from the ones found in the Burgess, we dont see the small slot like openings in the conchs that the Helens extended through, nor the rounded bulges in the conchs for the same purpose seen in other hyolithids.  A bit of soft bodied preservation might have been nice here!