Indiana Ordovician Bivalve ID

[Nimravis]

Over the weekend I found this bivalve while collecting at the St. Leon, Indiana roadcut. I posted it in the Hunting Trip section, but received no ID on this piece, so I figured that I would put it here to see if some Member could give me an ID. I have never found one like this before nor can I find a similar one while checking various web pages. Thanks 

 

[Micah]

Do you know what formation the particular road cut you found this bivalve is in? This is a good resource for Indiana fossils,  but I didn’t see anything matching your shell on this or other resources I looked at... sorry I wasn’t more help. The closest I can find is Ischyrodonta elongata, but it lacks some of the shape and zigzagging of the ridges your specimen has.

[doushantuo]

Reticulate ornament would suggest a cryptodont,or praecardiid?

Ontaria,Cardiola?

[Nimravis]

1 hour ago, Micah said:

Do you know what formation the particular road cut you found this bivalve is in?

The St. Leon Road cut exposes the Whitewater, Liberty, Waynesville and Arnheim Formations.

[Nimravis]

1 hour ago, doushantuo said:

Reticulate ornament would suggest a cryptodont,or praecardiid?

Ontaria,Cardiola?

Thanks I will have a look.

[Shamalama]

Reach out to the Dry Dredgers  fossil club in Cincinnati. They have some experts that will be able to ID that rare beauty. Quite the unusual growth line ornamentation for sure!

[Nimravis]

1 hour ago, Shamalama said:

Reach out to the Dry Dredgers  fossil club in Cincinnati. They have some experts that will be able to ID that rare beauty. Quite the unusual growth line ornamentation for sure!

I belong to that group, but have never met any of them of had contact with them- I just like to support various clubs-  I will do that though

[erose]

Caritodens welchi (James)

 

I have a few of these and they are really sweet.

 

[Nimravis]

26 minutes ago, erose said:

Caritodens welchi (James)

 

I have a few of these and they are really sweet.

 

Thanks much.

[Nimravis]

k

[Nimravis]

On 10/14/2019 at 9:55 PM, Micah said:

Do you know what formation the particular road cut you found this bivalve is in? This is a good resource for Indiana fossils,  but I didn’t see anything matching your shell on this or other resources I looked at... sorry I wasn’t more help. The closest I can find is Ischyrodonta elongata, but it lacks some of the shape and zigzagging of the ridges your specimen has.

Thanks

[Micah]

13 hours ago, erose said:

Caritodens welchi (James)

 

I have a few of these and they are really sweet.

 

What resource did you use to id this? I can’t find mention of this in my resources....

[D.N.FossilmanLithuania]

Looks similar to pteriomorph or ambonychiid, I find similar shells in Silurian.

 

[erose]

9 hours ago, Micah said:

What resource did you use to id this? I can’t find mention of this in my resources....

 

https://pubs.usgs.gov/pp/0695/report.pdf

 

It is listed on the UG stratigraphy site as well: http://strata.uga.edu/cincy/fauna/bivalvia/Caritodens.html

[doushantuo]

Actinopteriid? 

[piranha]

Carlton Brett replied:

 

This is a pterioid bivalve but of course not Caritodens.  I do not know the genus; not in the Atlas of Ordovician Life nor Steve Holland’s website, nor the Cincinnatian fossils book.  In what part of the Rte 1 outcrop did you find this?  Perhaps it is a part of the Whitewater fauna?

[erose]

1 hour ago, piranha said:

Carlton Brett replied:

 

This is a pterioid bivalve but of course not Caritodens.  I do not know the genus; not in the Atlas of Ordovician Life nor Steve Holland’s website, nor the Cincinnatian fossils book.  In what part of the Rte 1 outcrop did you find this?  Perhaps it is a part of the Whitewater fauna?

Pojeta (1971) has an image that isn't quite as ornate but it is the closest I could find online. I will have to look at my catalog and see what my final reference was. I suspect it was in one of the other pubs by Pojeta on bivalves or maybe even the original by James.  My Cinci library is fairly extensive so give me a day....

 

I remember this species well as they are so uniquely ornate and I worked hard to find the proper identification.

 

PS Pojeta has it listed as Pterinea welchi (James).  Holland has it listed as Caritodens welchi (James) and listed as being a Liberty species.

[doushantuo]

Actually,i am struck by that ornament.*

Like you said,it's very distinctive.

What i could find that was remotely similar is not strictly Ordovician,an/or perhaps not part of the relevant bioprovince.

* perhaps more in an esthetic way than anything else 

[connorp]

@Nimravis Did you ever get a definitive ID for this bivalve? I just came across this thread while trying to ID a similar specimen I found in the Liberty Formation at St. Leon.

[Nimravis]

3 hours ago, connorp said:

Did you ever get a definitive ID for this bivalve? I just came across this thread while trying to ID a similar specimen I found in the Liberty Formation at St. Leon.

Totally forgot about this piece. Just the info that is listed above. I thought I contacted the Dry Dredgers, will check to see if I ever received a response. That is a pretty one that you have.

[Nimravis]

@connorp FYI, I just checked my old e-mails and see that I did e-mail a member of the Dry Dredgers and he stated the following:

 

The clam is Caritodens. It is the only one in the area that has shell preservation. The ornamentation is typical of larger ones.

 

@erose also stated that it was the same thing during my initial post.

[erose]

3 hours ago, Nimravis said:

@connorp FYI, I just checked my old e-mails and see that I did e-mail a member of the Dry Dredgers and he stated the following:

 

The clam is Caritodens. It is the only one in the area that has shell preservation. The ornamentation is typical of larger ones.

 

@erose also stated that it was the same thing during my initial post.

 Caritodens is closer to oysters. Different shell calcite and different preservation.

 

[erose]

Major Edit - had it backwards!

 

So molluscs make their shells from calcite. They can either be a straight up calcite or the variation known as aragonite.  Apparently the aragonitic forms show up earlier in time but the two types are already established by the Ordovician if not earlier.  Oysters and pectens are the two main types of bivalves that use calcite.  Their shells tend to be fossilized where the aragonitic forms tend to dissolve over time. In gastropods the platycerids(sp?) also use more calcite.  The result in the fossil record is that we either find fossilized shell or we only find internal molds aka steinkerns. This is true for both the limestone-rich Cincinnatian and the Cretaceous of Central Texas.

 

In the Cincinnatian things like Caritodens, a bivalve, in the pectin group and Cyclonema, a gastropod, in the platycerid group are found with fossilized shell. Where almost all other bivalves and gastropods are only found as internal molds.   The same holds true in Texas. Oysters, pectins and muscles as well as some tiny platycerid-type  snails preserve shell. Everything else is a steinkern.

 

Having collected both areas the similarities are obvious.