Cambrian Problematica - Any thoughts?

[Arizona Chris]

Hi all,

Now here's a tough one!  As you may know, we have been extensively documenting many of our finds from a new locality in the middle Cambrian Bright Angel shale of northern Arizona, and have found superb preservation on molts of hordes of rare Zacanthoides trilobites.  But - besides the hyalithids and occasional inarticulate brach, we find something very peculiar.  Both mixed in with the trilobite beds and in a bed all their own about a few inches lower, we find this fossil, best described as "bundles of tubes" in quite an abundance.  I have lots of photos we took under magnification, and our guess as to what this may have looked like which Ill post here.  We have had a number of professional paleontologists look at these, and they just threw their arms up in the air.  So here is what we know at this point after examining hundreds of specimens:

1.  We never find solitary tubes
2.  90% of them are preserved upright in life position
3.  10% are found laying on thier sides with the trilobites so they cant be rhizomes or burrows.
4.  Length varies from 1 - 3cm and goes through multiple layers of shale vertically.
5.  No internal septa, tabulae or partitions, or branching.
6.  Some have a tapered profile
7.  cross sections are hexagonal in center, round on edges
8.  separate tubes are .5 - 1mm dia
9. no sponge spicules seen at any magnification, and no osculum.

 

Ok, so here are some shots with the microscope:

1.  Cross sections at 10x

 

 

2.  Side views paralell to bedding plane

 

 

 

3.  Our best interpretation of what the animal may have looked like so far (dont laugh - Im no paleo artist!)

 

Now I dont want to steer you into any conclusions, but our thoughts are a colonial hydrozoan or cnidarian, or some kind of strange holdfast or anchor for an animal.  I dont think an algae or sea weed would have polygonal structures like this.  Any thoughts on this will be greatly appreciated!

[Miocene_Mason]

Maybe paleodictyon ? That's just a guess.

[Arizona Chris]

This wouldnt be a trace fossil, it goes 2 - 3cm into the sediment as sharp edged tubes.  Also the size is very tiny!

[fossilcrazy]

Hi Arizona Chris,  I remember your blogs from many years ago. You found some Hyolithids in the Bright Angel and I think you also found Cambrorhytia.  Well once again you have some curious Cambrians. I'm not prepared to propose a fossil name for you. It might take a heavy hitter Cambrian researcher to figure this one out. Hope someone weighs in and comes up with a candidate.  

[fossilcrazy]

Chris, Check out this publication:  https://www.researchgate.net/publication/304109462_Ecology_and_evolution_of_Cambrian_reefs

 

The branching monocyathid  Archaeolynthus has a resemblance to the form or your fossil. There aren't a whole lot of candidates from the Cambrian. 

[piranha]

It looks similar to Harklessia yuenglingensis, from the Lower Cambrian of Nevada.

 

"Close-packed, cerioid, polygonal to subpolygonal corallites forming hemispherical to spheroidal masses.  Corallites range in diameter from 1.2 to 3.2 mm; individual corallites are greater than 25 mm long.  Corallites curve or undulate, fanning outward from a centralized area.  All corallites share walls.  All corallites lack septa, tabulae, and mural pores."

 

Hicks, M. (2006)

A new genus of Early Cambrian coral in Esmeralda County, southwestern Nevada.

Journal of Paleontology, 80(4):609-615

 

[doushantuo]

Having just taken a peek at the piece Piranha mentioned,I tend to agree.

 

hickscambriJOPincsediscorcnidacoel06o%3B2.pdf

[doushantuo]

(pseudo)hexagonal packing seems to be rather common in Paleozoic clonal organisms

[Arizona Chris]

Well so far, thats the closest match to anything Ive seen.  Gives me a starting point for researching this enigmatic fossil.  the My patterns on the end dont exactly match but we could have a slightly different species here.  My drawing seems a pretty good match!  Any one else have any ideas?  bundles of tube worms?  Just thinking out loud.  

[TqB]

It seems that the hexagons have shared walls - does that rule out worm tubes? Piranha's coral link is persuasive.

[Arizona Chris]

Well my first thoughts of this being a colonial hydrozoan or cnidarian appear to have been on the right track.  After reading the paper provided by Piranha, there can be no doubt that this is such an animal.  Of the three major coralomorphs discussed in the correct time period in the Ollenellus zone, the closest topographically by far is the one from Nevada - Harklessia.  This adds the last piece to the puzzle of the environment in which the Zacanthoides trilobites lived in.  A mid depth continental shelf environment with a muddy hardrground filled with inarticulate brachs (Billingslella), primitive trilobites (Zacanthoides), large numbers of hyolithids (hyolithes) and of course now small spherical corals with tiny hexagonal calices.  Interestingly enough, the bulletins and papers I have seen on the Grand Canyon BAS fauna did not mention these coralomorphs perhaps due to their rarity or perhaps insignificance.  This certainly makes our BAS locality near Ashfork Arizona a very special one!