Adam's Ordovician.

[Misha]

Those strophomenids are so beautiful!

[minnbuckeye]

9 hours ago, Tidgy's Dad said:

preservation bias or collecting bias

In my case, a collection bias for sure!!

[Tidgy's Dad]

On 3/4/2021 at 4:25 PM, Misha said:

Those strophomenids are so beautiful!

 

On 3/4/2021 at 4:33 PM, minnbuckeye said:

In my case, a collection bias for sure!!

And this thread has just achieved 20,000 views, so thanks guys, and thanks to everyone else who's looked in over the years, commented, 'liked' or just had a peek. Much appreciated and I hope this has been of some use to some people and enjoyable as well. 

Thank you all!  

[Tidgy's Dad]

Some bryozoans from these St. Leon hash pieces. Unsurprisingly, bryozoans are the most common fossils I find in these Cincinnatian pieces. 

This shows two of the most common tiny (1-2mm wide) bryozoans from St. Leon. The one on the left I think is Batostoma with the zooecia closely packed and mesozooecia between them sometimes, and the one on the right with oval, more widely spaced zooecia could be Bythopora deliculata. Maybe. 

Bythopora deliculata and some trilobits and crinoid ossicles :

Bythopora?

 

Batostoma?

A couple of small colonies encrusting a Strophomena planumbona brachiopod

A lovely disc bryozoan : 

I think the one near the top with very long thin zooecia in straight lines separated by straight ridges is Stictopora emacerata.

.  

 

[FossilNerd]

3 hours ago, Tidgy's Dad said:

And this thread has just achieved 20,000 views, so thanks guys, and thanks to everyone else who's looked in over the years, commented, 'liked' or just had a peek. Much appreciated and I hope this has been of some use to some people and enjoyable as well. 

Thank you all!

Congrats Adam! I have learned a thing or two from your thread, enjoyed your many posts/pictures, and identified a few specimens with your unknowing help.  
 

I recommend this thread (and your similar ones) to everyone. Thanks for creating, posting, and maintaining it. May it get 20,000 more views!

[Tidgy's Dad]

On 3/6/2021 at 2:34 AM, FossilNerd said:

Congrats Adam! I have learned a thing or two from your thread, enjoyed your many posts/pictures, and identified a few specimens with your unknowing help.  
 

I recommend this thread (and your similar ones) to everyone. Thanks for creating, posting, and maintaining it. May it get 20,000 more views!

Thanks, Wayne, your contributions have also been most welcome and appreciated.

This one's a mystery. I've put it on the Id. thread in the hope someone can help.

I hope it's Pseudolingula vanhornei which would fit the shape and growth lines, but the ribs and tubercles are wrong. Also the detail looks more like a bryozoan, so perhaps a bryozoan is covering the brachiopod. I don't think it's just a bryozoan, but maybe a trilobit? A trilobit such as a hypostome covered by a bryozoan?

It's 4 mm wide and rises slightly in steps at each growth line but only attains a maximum height of a mm or perhaps a little more.

Hmmm.

It has been suggested to me that it could be Petrocrania. P. scabiosa does occur in these formations and though it usually grows on Rafinesquina valves, it could here be growing over the shell of a more ribbed brachiopod such as an orthid. Petrocrania often follows the contours of the host shell. There even seems to be an uncovered fragment of shell just above the main fossil, while the rest of the brachiopod has presumably broken off if this is the encrusting species Petrocrania scabiosa.  Thanks to @Al Dente for this excellent idea.

This first photo also has a tiny Zygospira modesta in shot :

Close-up :

 

[Tidgy's Dad]

A tiny (3 mm long) Cornulites flexuosus on the inside of a Strophomena planumbona valve. It is orientated, as they often are; to face the anterior where the valves open as they feed off the currents generated by the brachiopod to supply food to its own lophophores.  It is also possible the cornulitid grew here after the death of the brachiopod.

This one's on an Eochonetes clarksvillensis shell exterior  Rather battered, I'm afraid.

And a third specimen next to a Flexicalymene thorax segment : 

:

 

 

 

[Tidgy's Dad]

A fragment of the bellerophontid gastropod (previously a monoplacophoran, but not at the moment, I think!) Phragmolites dyeri. 

About 1 cm long and 1.5 mm wide, but very pretty indeed. 

Thanks very much to @connorp for this id. 

[Tidgy's Dad]

Having accidentally stumbled upon a gastropod, I'll post the others from St. Leon that I have. These are my first snails from St Leon, so it's great to have a few more of the species from this location to add to my collection. 

The two on the left are internal molds of Paupospira bowdeni which I also have from older deposits at Lawrenceburg. 

There is a bit of another specimen stuck in the rock at the bottom of this first example : 

The other specimen : 

[Tidgy's Dad]

The specimen on the right in the first photo of the above post is broader and more conical. I think it's the internal mold of Cyclonema bilix. I have a couple of species of Cyclonema from earlier in the Ordovician, but this species is new for me. 

[Tidgy's Dad]

Everyone loves trilobites. How could one not? 

Even partials or trilobits like these from the rocks shown above and from this other hash from St. Leon. This new piece, like some of the others contains the distinctive square columnals of the crinoid Xenocrinus baeri so should be Liberty Formation. 

A coupe of stem ossicles from Xenocrinus baeri, lots of the other fragments look possible trilobits to me: 

The most common identifiable trilobits are the thorax segments of Flexicalymene, most likely F. meeki, I think. These would have been shed during molting as the trilobite was growing. I've already posted a few included with other finds in the posts above.

This first one is 6 mm wide, what is left of it.

This one is 14 mm across :

Smaller segments :

There were also a couple of cranidia, this one is tiny - 3 mm.

This one's much bigger at 6 mm long :

A librigena (free cheek) : 

A couple of quite wonderful little Flexicalymene hypostomes. 

This one's 2.5 mm from curve to tip :

 

And this one a little longer at 3 mm.

Closer look : 

 

 

 

 

 

 

[Tidgy's Dad]

This would appear to be an Isotelus hypostome, though it is missing the terracing one would expect to find.

It's about 2 cm long.

Details :

Don't know what this bit is.  trilobite free cheek with a spine or tubercle broke off?

The Isotelus hypostome rock also contained a Flexicalymene cranidium and at least three throrax segments which I posted earlier. 

It also contained some lovely Batostoma? bryozoans.

 Central one is 16 mm long :

It also contained some Eochonetes clarksvillensis.

Pedicle valve interior, 16 mm wide :

Concave brachial valves, 16 mm :

And a little one at 8 mm wide. 

[Tidgy's Dad]

And this last rock also contained a lot of ostracods. 

I don't know much about ostracods, the most common fossil arthropods are often overlooked because they're usually so tiny. Scale in mm. 

That's it from St. Leon. 

And once again a huge thank you to Ralph @Nimravis for all the wonderful specimens from this location shown above.

 

[Tidgy's Dad]

Shame on me, I almost forgot! 

Another commonly ignored group of fossils that are common and far more obvious than ostracods are crinoid stem sections. 

Here's a few from this last St. Leon collection.

The extremely stellate and rather beautiful ones are Plicodendrocrinus casei. Tiny Zygospira modesta in the field of view too :

The more pentagonal ones most likely Iocrinus subcrassus :

The 'wagon wheels' are Cincinnaticrinus pentagonus :

And the square ones are Xenocrinus baeri, limited to the Liberty Formation :

 

[Tidgy's Dad]

 

A new location for me, more specimens to add to my ever growing Cincinnatian collection.

These are from Bon Well Hill, near Brookville, Indiana and again kindly sent to me by my friend Ralph. @Nimravis

The rocks from this location seem to be primarily from the Richmondian Liberty Formation. 

The horn coral is Grewingkia canadensis which I also have from St. Leon. (see previous page) 2.4 cm long.

 

[Tidgy's Dad]

These beautiful Peronopra hospitalis ( was Homotrypella hospitalis ) are completely encrusting the pedicle valves of Rafinesquina brachiopods. Amazing.

This first one  is 35 mm wide, but a couple of mm of that have been added by the encrusting bryozoan.

 

You can't see the tiny, low monticules very well in the photos, they're much more obvious in real life, though this next photo, though blurred, does better show the monticules :

The reverse of this specimen shows the inner surface of the valve with the delthyrium, though adult Rafinesquina probably didn't have a pedicle, they just lay flat, convex side-up, on the muddy sediments of the ocean floor and thus were often encrusted by various other organisms as they were sometimes the only anchorage points available.  Whether or not this encrustation took place while the brachiopod was alive or post mortem, I cannot tell. You can see how thick the bryozoan is around the edges of the valve, but it doesn't grow onto the valve interior. 

 

Close up of the delthyrium, the bryozoan is 1 mm thick here :

2 mm thick in places :

The second specimen is 3.4 cm wide : 

The reverse of this one is the concave brachial valve. Again bryozoan free. 

It looks convex in the photo above, but it's actually very concave :

Brachial valve details :

The detail of the microstructure is simply stunningly beautiful  :

Trying to catch the monticules :

 

[FossilNerd]

55 minutes ago, Tidgy's Dad said:

The reverse of this specimen shows the inner surface of the valve with the delthyrium, though adult Rafinesquina probably didn't have a pedicle, they just lay flat, convex side-up, on the muddy sediments of the ocean floor and thus were often encrusted by various other organisms as they were sometimes the only anchorage points available.  

 

I love these specimens Adam! 

 

I often find Rafinesquina encrusted with one form of life or another. Many of the layers in areas that I find them, were laid down during turbulent times, and the valves are often broken and/or piled on top of one another. The ones that are whole, or at least semi-whole, are usually encrusted with a bryozoan that helped hold it together. I’m not sure that I have ever found a whole, matrix free one, that was clean of other critters.

 

The adults just laying on the ocean floor without a pedicle would support my findings. I can imagine that they would wash around, break, and/or pile up easier during a storm with nothing to anchor them down. 

[Tidgy's Dad]

On 3/11/2021 at 7:40 PM, FossilNerd said:

 

I often find Rafinesquina encrusted with one form of life or another. Many of the layers in areas that I find them, were laid down during turbulent times, and the valves are often broken and/or piled on top of one another. The ones that are whole, or at least semi-whole, are usually encrusted with a bryozoan that helped hold it together. I’m not sure that I have ever found a whole, matrix free one, that was clean of other critters.

Some species of Rafinesquina had much thinner shells that others. R. fracta and the older R. trentonensis have very thin shells and are usually found broken, while other forms such as these late Cincinnatian R. alternata and R. ponderosa are thicker shelled and often survive as complete valves, separated or still articulated. I guess you are searching higher energy environments of deposition and / or more fragile species, while many of these Indiana sites seem to have the opposite. 

I have found inarticulate brachiopods (Petrocrania scabiosa, Philhedra.), crinoid holdfasts, a wealth of bryozoa, and an edrioasteroid on various specimens but other things can be found too such as conulitids and the coral Protaraea. 

I do have some that I posted free of epibionts. 

 

And here are two from Bon Well Hill that appear encrustation free. (though there is still some matrix that I haven't yet removed.)

 

Notice the hinge and interarea are visible on the concave side, confirming they are Rafinesquina, Strophomena has the reverse with these features visible on the convex side. 

 

Notice the height difference at the anterior end of the two specimens. The two species commonly found at Bon Well Hill are Rafinesquina alternata and Rafinesquina ponderosa. R.ponderosa can be 4 to 6 cm wide, R. alternata 3 to5, so there is some overlap, R. ponderosa is usually thin, like the one on the right, whereas R. alternata can be variable; from very thin to high at the anterior, so again there is possible overlap between the two.

The other notable supposed difference is that R. alternata has more obvious striae that alternate between one thick and several thin, while R. ponderosa has less obvious and more equal sized striae. But again there is overlap and some suggest they are varieties of the same species which is true of a lot of other species too. 

 

A close up of the tall one with alternating ribs, which to me, along with the size and shape, suggests Rafinesquina alternata. 

 

 

On the flat specimen the ribs appear more even in places but alternating in others. 

 

It also has an area of interesting abnormal growth ; 

 

Beak. 

 

[FossilNerd]

7 hours ago, Tidgy's Dad said:

I guess you are searching higher energy environments of deposition and / or more fragile species,

 

I'll have to check my notes later, but I think that I have been finding R. alternata in a late Cincinnatian layer (Grant Lake Limestone). I'm guessing the deposit (or some of it) was created under a high energy event. I often find them in what I call "death stacks" with multiple individuals stacked on top of each other. Their valve shapes do make for an easier time of stacking with one being concave and the other convex. I'll post a few pictures when I get home if that is alright.

 

Thanks for the comparisons of the Bon Well Hill specimens.   Very helpful photos and descriptions. Like you, I also think that some species should be grouped together, and that many are just variations of the same. That goes for more than just brachiopods.

[Tidgy's Dad]

14 hours ago, FossilNerd said:

 

I'll have to check my notes later, but I think that I have been finding R. alternata in a late Cincinnatian layer (Grant Lake Limestone). I'm guessing the deposit (or some of it) was created under a high energy event. I often find them in what I call "death stacks" with multiple individuals stacked on top of each other. Their valve shapes do make for an easier time of stacking with one being concave and the other convex. I'll post a few pictures when I get home if that is alright.

 

Thanks for the comparisons of the Bon Well Hill specimens.   Very helpful photos and descriptions. Like you, I also think that some species should be grouped together, and that many are just variations of the same. That goes for more than just brachiopods.

I am not familiar with the Grant Lake Limestone, though that sounds like high energy deposition to me. Possibly storm washed death assemblages. 

Please do post a photo or two, it would be most interesting and complimentary to this part of the thread. 

Palaeontologists seem to be fairly evenly split between lumpers and splitters, some will split a genus up into loads of species and then another person will lump them all together again. I am more of a lumper than a splitter when it comes to brachiopods in particular as I understand the huge variance in form that can occur within a species in just a single location, let alone over time, in different locations and environmental conditions. Not that I oppose splitting when it's clearly a different species.

Lumping also makes life easier for ids, of course. 

[Tidgy's Dad]

Here is another example of one of my favourite brachiopod genera, Leptaena. This one's Leptaena richmondensis from Bon Well Hill. I also have this species from St. Leon, but this is my first specimen free from matrix. Lovely. 

2.3 cm wide, 

Pedicle valve is convex and steeply stepped near anterior margin :

 

Slightly concave brachial valve : 

Hinge-line :

Commissure : 

Side view :

Detail :

 

 

 

[ClearLake]

Thanks Adam for showing all of these and explaining the variations. I have collected from most of these recent localities you have been showing and the Cincinnatian material is still one of my favorites. 

[FossilNerd]

On 3/12/2021 at 11:00 PM, Tidgy's Dad said:

Please do post a photo or two, it would be most interesting and complimentary to this part of the thread. 

Here is a handful of pictures.  

 

These are two of what I believe to be Rafinesquina alternata. They are covered by a thin layer of bryozoan that seem to have held them together, and so mostly whole. 
 

I was correct in remembering that they are from the Grant Lake Limestone (equivalent to the McMillan Formation in older text).

 

The one on the left is bigger than the one on the right, and the largest (mostly) whole one in my collection. 
 

 

Here is a shot to help show how they differ in size and height.

 

 

These mostly whole specimens are rarer in the exposure that I find them. Usually they are broken or stacked together like the ones below.

 

 

 

[Tidgy's Dad]

21 hours ago, ClearLake said:

Thanks Adam for showing all of these and explaining the variations. I have collected from most of these recent localities you have been showing and the Cincinnatian material is still one of my favorites. 

I agree. This Cincinnatian material is fabulous and I have quite a collection from several sites now, thanks largely to the generosity of forum members. I have a little more from Bon Well Hill to add here, then my first material from Garr Hill, then some Ohio specimens followed by some roughly equivalent Georgian Bay and Verulam Formation fossils from Canada. 

Happy days!  

[Tidgy's Dad]

1 hour ago, FossilNerd said:

Here is a handful of pictures.  

 

These are two of what I believe to be Rafinesquina alternata. They are covered by a thin layer of bryozoan that seem to have held them together, and so mostly whole. 
 

I was correct in remembering that they are from the Grant Lake Limestone (equivalent to the McMillan Formation in older text).

 

The one on the left is bigger than the one on the right, and the largest (mostly) whole one in my collection. 

Thanks, Wayne, very nice specimens. 

The big one is a really decent size and judging by that and the relative equality of size of the striae, would be Rafinesquina ponderosa. The one on the right, too, probably.

The stacked ones are R. alternata.