Learning to tell some brachiopods apart

[BobWill]

I'm trying to tell some of my brachiopods from Jacksboro Texas apart but the information I can find is confusing. I would like  to see any examples of isolated pedicle valves of Marginifera lasallensis, Retaria lasallensis and Kutorginella lasallensis.  They are about 2 cm wide, 1 cm deep and 1 cm tall, with a wide heart-shaped appearance and two delicate triangular ears that often break off. They also have 10-14 wrinkles near the nose with the smaller valve almost completely flat and the larger valve very curved, ending in a delicate scooping trail. They tend to occur in upper Misssourian and low to mid-Virgilian formations from Texas to Illinois. I would like pictures of the inside of the flat valve, lit from the side to enhance contrast if possible. Thanks for any help.        

[Mediospirifer]

I think your 3 species are likely the same. It's not uncommon for species to be reclassified into a different genus, keeping the same species name.

 

Fossilworks lists Kutorginella lasallensis as the current accepted name, with Marginifera lasallensis, Retaria lasallensis, and Productus lasallensis as alternative combinations.

 

This would explain your difficulty in telling them apart!

 

[fossilnut]

@BobWillWhat an interesting sounding description. Would you please post some pictures. I for one would like to see one. Thanks

[grandpa]

1 hour ago, Mediospirifer said:

I think your 3 species are likely the same

Adding to @Mediospirifer and Fossilworks, I found this from:

The effects of predation on the preservation of ontogenetically young individuals by Purden, Matthew J. et al  https://www.researchgate.net/publication/320953682_The_effects_of_predation_on_the_preservation_of_ontogenetically_young_individuals

 

"One biconvex, Composita subtilita, and one concavo-convex taxon, Kutorginella lasallensis (= Retaria lasallensis of Muir-Wood and Cooper 1960) (Fig. 3A and B), were examined from this unit. " 

 

I also found this topic broached in a past TFF post.  To refresh our memories:

So, Bob, does this address your question, or are you thinking that the 3 still might each be a separate genus and are looking for detail to define the differences in each genus?

[grandpa]

3 minutes ago, fossilnut said:

Would you please post some pictures. I for one would like to see one

@fossilnut See Rodney Wise's website TxFossils page on Jacksboro brachs for some quality photos of this and other brachs of the area at:

 

https://www.txfossils.com/brachiopods-jack-county/

[fossilnut]

@grandpaThanks. What a rich fauna.

[BobWill]

2 hours ago, Mediospirifer said:

I think your 3 species are likely the same. It's not uncommon for species to be reclassified into a different genus, keeping the same species name.

 

Fossilworks lists Kutorginella lasallensis as the current accepted name, with Marginifera lasallensis, Retaria lasallensis, and Productus lasallensis as alternative combinations.

 

This would explain your difficulty in telling them apart!

 

This is indeed the crux of the question. Are they really the same? The request for the rare internal views may help tell whether some possible differences that seem to be showing up are real or imagined. If you have any separated brachial valves I would love to see a photo of the inside.

[BobWill]

45 minutes ago, fossilnut said:

@grandpaThanks. What a rich fauna.

It is a very rich fauna and that is one of the reasons some of us at the Dallas Paleontological Society started a study group. There is so much to study and so much to learn about the Pennsylvanian fossils of Texas. Rodney Wise is also a member of that group. Another good website for all fossils from here is Lance Hall's site here.                         http://www.northtexasfossils.com/

It also includes a lot from Jacksboro and other Pennsylvanian sites. The diversity and excellent preservation is one of the reasons the Finis Shale is included in the new "Liberation Lagerstätte" designation.

[Mediospirifer]

1 hour ago, BobWill said:

This is indeed the crux of the question. Are they really the same? The request for the rare internal views may help tell whether some possible differences that seem to be showing up are real or imagined. If you have any separated brachial valves I would love to see a photo of the inside.

 

Not in my collection, sorry. My brachiopods are mostly Ordovician and Devonian. 

 

I'd recommend looking up the references listed for the species in Fossilworks, to see if they are reassigning an existing species to a different genus. The Fossilworks entry, as written, suggests to me that this is the case. For what it's worth, while I'm not familiar with the species you're dealing with, I have seen multiple examples of that happening with species that I do have experience with. I've also seen reference plates where there are several specimens of the same species pictured, where some are visibly different from others (enough to make me wonder whether they should be the same species or not).

 

Good luck. 

 

[erose]

It is very unusual to find two similar genera with the same specific name in a known fauna. Without my usual references I am going to say they are all the same thing.   But there are exceptions, especially in faunas that were studied in the 1800's and early 1900's when communication amongst researchers was slim and slow.

 

There are occasions when a "specific epithet" is used for two different genera in the same fauna. In the Cincinnatian Series (Upper Ordovician) you can find both Rafinesquina ponderosa as well as Vinlandostrophia ponderosa. But one is a strophomenid and the other a rhynchonellid, respectively. They are very different and not easily confused.  BUT both are large for their genus, and were each given the specific name "ponderosa."
 

But man-o-man I know how confusing those Pennsylvanian productids can be. Most are not complete and there is definitely some variability in things like number of spines or degree of convexity.  Not to mention that for some brachiopods you need well preserved interior structures to know for sure what species is in hand.

 

Write everything in PENCIL and keep the eraser near by.....