How common planispiral Paleozoic Monoplacophorans?

[Arizona Chris]

Were finding dozens of what we believe to be some small flat coiled monoplacophorans in some Permian sediments.  The spirals dont touch and sometimes the openings are not round.  I was surprised to find that other than the normal cap shaped ones we find a lot of, the were also many with half a dozen coils.  Ever found this type?  Id be interested to see if what we  have is similar.  

[ynot]

3 hours ago, Arizona Chris said:

Were finding dozens of what we believe to be some small flat coiled monoplacophorans in some Permian sediments.  The spirals dont touch and sometimes the openings are not round.  I was surprised to find that other than the normal cap shaped ones we find a lot of, the were also many with half a dozen coils.  Ever found this type?  Id be interested to see if what we  have is similar.  

Got any pictures?

[Arizona Chris]

Ok, here is a shot at 20x.  They are flat on both sides, some of them are round tubes.  Im thinking either archeogastropod or monoplacophoran.  

[ynot]

Sorry I can not help with Your quest, but those do look nice.

[DPS Ammonite]

Could they be baby/partial Straparollus sp. coiled gastropods as pictured in the Winter's reference?

[Arizona Chris]

That is possible too, its not everyday you find such small straparollus!

[Jackson g]

I would lean more towards the archaeogastropoda. I have many monoplacophorans and couple different species at that, and the picture looks nothing like what I've got. Here's a coiled one I have partially prepped below for reference.

[ashcraft]

On 4/4/2019 at 8:45 AM, Jackson g said:

I would lean more towards the archaeogastropoda. I have many monoplacophorans and couple different species at that, and the picture looks nothing like what I've got. Here's a coiled one I have partially prepped below for reference.

+1

[DPS Ammonite]

They look much more like Straparollus which S. S. Winters has found in the Permian Fort Apache Limestone where Cris found his.

 

See Straparollus shells 3a-3c from:

Winters, S.S. (1963). Supai Formation (Permian) of Eastern Arizona. Geological Society of America Memoir, 89, 99 p

[erose]

Straparollus and similar genera are not monoplacophorans, but they are gastropods with a very low, almost planispiral, form. They are very common in some Carboniferous and Permian formations.

 

Also, IMHO the image Kackson G shared is the "platycerid" Orthonychia, again not a monoplacophoran.

[Jackson g]

Agreed with @DPS Ammonite. Not sure I quite agree these are gastropods yet though. Either or they are mollusks I know. I've been told by some in person they are gastropods, and by others they are monoplacophorans. Im no paleontologist though, and much too busy with working right now on the road to be able to check anything at home. I can say with 100% certainty though, that all the gastropod fossils (I can identify) collected in the same area are much different looking than these. Much more like your common snail shell. When I'm back home I'll take them to a friend at MU to checkout.

[DPS Ammonite]

On 4/5/2019 at 1:39 PM, DPS Ammonite said:

They look much more like Straparollus which S. S. Winters has found in the Permian Fort Apache Limestone where Cris found his.

 

See Straparollus shells 3a-3c from:

Winters, S.S. (1963). Supai Formation (Permian) of Eastern Arizona. Geological Society of America Memoir, 89, 99 p

I should have pointed out that above post was referring to the fossils that Arizona Chris posted.

[Jackson g]

On 4/5/2019 at 8:38 PM, erose said:

Also, IMHO the image Kackson G shared is the "platycerid" Orthonychia, again not a monoplacophoran

You were correct on the ID on this one, good call and thank you. I passed on the info you said as well. I just got some of my specimens and a letter back in the mail. I sent some coiled, some smooth ovaled shaped cones, and some straight almost spike coned looking ones. His opinion was most were gastropods, and only a couple were true placos. Great to learn some local info.