Brachiopods from the Permian of Arizona

[Arizona Chris]

Hello all,

 

Another small project completed for our seemingly never ending study of the Lower Permian Fort Apache Limestone east of Payson Arizona.  This week, we have put together all the images and data from the hordes of productids (with spines) and one teensy brach found in the acid fines.  

 

 Brachiopods are a minor faunal element in the Fort Apache Limestones, nearly 100% were found as Productids and their hordes of tiny spines. Only ONE other brach was found, and it was microscopic in size at a size of 1 mm. No doubt the large amount of mud and silt raining down on the bottom of the Fort Apache Sea made life very difficult for any type of filter feeders. Largely missing as well are corals, crinoids and sponges which also feed by filtering the muddy waters. Only the Productids seemed to be adapted to such conditions.

Both silicified and calcified fossils were found. Some of the silicified fossils were very delicate and had many of the spines still attached when dissolved out of the limestones with muriatic acid. Winters in his monumental GSA memoir 89 identifies the productids as Bellaclathrus spinosus, and the tiny brach as Pseudodielasma sp. Since this is a very generic looking brachiopod, well go with his identification.

 

Pseudodielasma sp. top view, pedical valve. This brach is the size of a pinhead and is the only one found after processing over 200 pounds in limestones! 45x

 

Pseudodielasma sp. bottom view, brachial valve. Here you can see the opening at the top for the pedicle to emerge for external support on a hard substrate. 45x

 

Bellaclathrus spinosus, only about an inch across it is far smaller than the average size of the productids found in the overlying Permian Kaibab formation. This one is calcified on the surface of the limestone found by cracking open large rocks. 2x

 

Bellaclathrus spinosus - very flat upper valve that is calcified. 3x

 

Bellaclathrus spinosus - Silicified specimens show much external detail. But they are hollow and very delicate! Notice the spine coming off the wings. 2x

 

Bellaclathrus spinosus - We found hordes of loose productid spines in the limestones. 7x

 

Bellaclathrus spinosus - Close up at 20x of some of the spines. Most are hollow tubes, and never come to a point. In life they are filled with live tissue and the spines grow by adding on to the ends.

 

 

Bellaclathrus spinosus - Two spines on a common base which was once the outermost layers in the productid shell. 20x.

 

Well, thats it for this week.  Hope you enjoyed our little presentation!

 

 

 

 

 

[Miocene_Mason]

Nice, I'm not used to seeing spiny Brachiopods with spines still attached!

[ynot]

You sure di find some unique pieces in Your desolved rock.

You aslo do very nice pictures.

Thanks for sharing these wonderful little fossils.

[DPS Ammonite]

Lots of cool stuff. When you finish you will have to publish the updated paleontology of the Fort Apache Limestone. Have you ever found any identifiable (genus, species) ammonites?

 

BTW, how many gallons of acid have you used to dissolve the limestone?

[Arizona Chris]

Thanks guys!  DPS_Ammonite - Only nautiloids here, too soon for ammonites.  One that is 10 inches planispiral, and one 2 inch orthocone.  Ive gone through 4-5 gal a week in acid.  At $10 a gallon from ACE, its getting pretty expensive!  We did the last load this week.  I finally had to decide - food or muriatic acid.

[MarcoSr]

Why are you using muriatic acid????????   Muriatic acid is a strong acid.  It not only dissolves the limestone (calcium carbonate) but also dissolves or damages most of the fossils in it.  Most shells are also  calcium carbonate and will dissolve quite easily in muriatic acid. Even phosphatic vertebrate fossils like shark teeth will be damaged/destroyed by muriatic acid.  Even when weaker acids like acetic or formic acid in low concentrations are used to dissolve limestone different chemical buffers are usually used to help protect the fossils.

 

Marco Sr.

[Arizona Chris]

MarcoSR - I am only interested in fossils preserved in pure silica.  The dilute muriatic I use will not damage them and the amount of fine details on the specimens is outrageous.  We have extracted fish teeth in Pennsylvanian limestones before, using acetic and I agree that is the best choice on these.  

[Fossildude19]

Very neat finds.  

Nice to see some love for the little stuff, here. 

 

[MarcoSr]

2 hours ago, Arizona Chris said:

MarcoSR - I am only interested in fossils preserved in pure silica.  The dilute muriatic I use will not damage them and the amount of fine details on the specimens is outrageous.  We have extracted fish teeth in Pennsylvanian limestones before, using acetic and I agree that is the best choice on these.  

 

I usually only care about the phosphatic vertebrate fossils when dissolving limestone so I do use weak concentrations of acetic acid ( 5% to 10%) which won't harm them.  However, even weak acids do dissolve some neat fossils like fish otolites.  I've seen even very dilute muriatic acid etch, dull the shine, and/or damage/dissolve shark and ray teeth so I never use it.  Plus in higher concentrations it shouldn't be used outside of a lab environment for safety reasons.  If you only care about fossils preserved in pure silica and understand that the muriatic acid is pretty much dissolving or damaging the rest of the fossils, very dilute muriatic acid will break down limestone quicker/easier than the weaker acids like acetic acid in low concentrations (5% to 10%).

 

But what you really have to be careful about is a lot of TFF members are not familiar at all with the chemicals used to break down different matrix types and TFF posts show up in Google searches.  Someone who doesn't understand acids and their dangers and/or doesn't understand the difference between how phosphatic or calcium carbonate or silica fossils react in acids can dissolve their specimens or, even worse, harm themselves thinking it is OK to use muriatic acid to dissolve limestone.  You didn't state that you used "dilute" muriatic acid (which can still be quite dangerous to use) in your original post.  You also stated that  " Both silicified and calcified fossils were found" which could easily be misinterpreted that muriatic acid doesn't harm calcified fossils.  You don't want some 10 year old kid hurting himself with muriatic acid after reading your post.  I don't like seeing any TFF posts that talk about using the stronger acids to dissolve different matrix types.  That is why I responded to your post.

 

 

Marco Sr.