Adam's Ordovician.

[Tidgy's Dad]

The bryozoan mentioned and shown on the previous page attached to a specimen of Rafinesquina alternata is Petigopora petechialis.

I think. 

Here are a few closer views:

 

[Tidgy's Dad]

The majority of the many epibionts growing on the R. ponderosa a few posts above it are the inarticulate craniid Petrocrania scabiosa, of which I posted another example on an R. ponderosa valve from the slightly younger Whitewater Formation back on page 11 of his thread.

Here are some close ups of the Fairview Formation Petrocrania scabiosa from Lawrenceburg.

 

[Tidgy's Dad]

For now, as I've finished my Lawrenceburg brachiopods, I'm going to move on to the road cutting at the Southgate Hill road cut, St Leon, Indiana and have a look at some specimens from there, also sent to me by the Remarkable Ralph @Nimravis. First up, here is one of my very favourite hash plates ever, a remarkable piece about 19 cm long and absolutely stuffed with bryozoans, brachiopods, crionoid columnals and, I think, fragments of trilobite. I'll give more detailed close-ups as I describe each species individually. 

The reverse :

 

 

 

[StevenJD]

That's a cool hash plate Adam, definitely loaded!

[Tidgy's Dad]

23 hours ago, StevenJD said:

That's a cool hash plate Adam, definitely loaded!

Thanks, Steven! 

I'll start off with a look at the bryozoa, beginning with lots of branching/ramose/stick, Trepostome specimens.

Some of these are probably Bythopora delicatula, but there are other species too

These specimens are from the hash shown above, but also from various other pieces that Ralph sent me. 

These first ones came free from the matrix, this one is 11 mm long.

And these one's much smaller, the tiniest is 3 mm long. 

Also little bits just a few mm long.

The bigger piece running through the middle from right to left below is 1.5 cm long, nice frondose specimen below it too : 

And the one below 6mm :

The beautiful one here is 2 cm from the base to the end of the longest branch :

And the field of vision below is 2.5 cm from right to left :

Tiny fragments only up to 4 mm long :

The cross section is about 2 mm across :

And finally, this one's 12 mm long :

 

 

[Tidgy's Dad]

Also on the hash plate are a couple of domed bryozoan colonies. I think they could be Homotrypella hospitalis, but I'm far from certain. 

This one is 1.2 cm at it's widest point excluding a little sticky-out bit on the edge which adds another 2 mm.

Close up :

Here's another specimen on the same hash, also 1.2 cm in diameter ; 

And up close :

And a side view to show the dome shape, it's about 3 mm high :

One more specimen, but this from a different rock from the same location and about the same size :

 

 

 

[Tidgy's Dad]

This bryozoan from the hash is Parvohallopora subnodosa, I think. 

This was one of the bryozoans from the area I was hoping to add to my collection.

2.2 cm long, here it is before prepping : 

And after prep :

You can see that the monticules are sort of in bands and are rounded, rather than sharp as in P. ramosa.

 

 

[Tidgy's Dad]

Just a quick diversion from the hash plate as I got diverted by another nice piece from St Leon.

This piece shows the orthid brachiopod Cincinnetina meeki and is probably from the Waynesville Formation of the Upper Ordovician. 

I like this because I also have C. multisecta from Lawrenceburg, so it's rather wonderful to see a successor species from a younger formation. 

That's a 1 cm cube. 

Notice also that there is some sort of ichnofossil, maybe burrows of something, seen extending from the top right down towards the centre in this rock. 

The reverse, notice one of the bryozoans I posted above :

Close-ups :

Inside of a brachial valve :

 

 

 

 

 

[Tidgy's Dad]

The burrows.

I wonder what made them?

[Tidgy's Dad]

Going back to the original hash plate, here are some Hebertella occidentalis brachiopods. 

This first one's a beauty, 2.8 cm across :

 

 

[Tidgy's Dad]

This one's a monster, 4 cm across, what there is of it, but the complete shell would have been bigger, of course. Interior of brachial valve.

I can't dig it out, because it's a lot to do and the matrix is pretty hard in this one, plus the fossil goes right through the rock and the top of it is missing so I'd just end up with a hole! 

And the interior of the pedicle valve of Hebertella alveata with it's muscle attachment scars. The shape is quite oval as opposed to the heart shaped scar of H. occidentalis .

Specimen is 2.5 cm wide, but again would have been bigger if complete. 

 

 

 

 

[Tidgy's Dad]

A smaller Hebertella, I think. 

This one is 1.7 cm across.

[FossilNerd]

2 hours ago, Tidgy's Dad said:

Going back to the original hash plate, here are some Hebertella occidentalis brachiopods.

This one is wonderful! Did you do any prep work or did nature expose her? 

[Tidgy's Dad]

2 hours ago, FossilNerd said:

This one is wonderful! Did you do any prep work or did nature expose her? 

Not much on this one. Just a bit of light pin prepping in the grooves on the shell and a bit of work at some of the margins.

Some of the others took a lot more work, like this little brachial valve interior, only 1 cm across, but quite tricky to remove the matrix from around the muscle attachment ridge and teeth. 

It's funny how sometimes a photo seems to reverse positive and negative :

This is how some of them are before prep. I didn't finish prepping this one because it's rather small, 1.5 cm across and it would be a bit much work.

But I did prep this tiny specimen a tad. 7 mm across.

What is interesting is that here we can see several specimens of square crinoid columnals. This is quite unusual, indeed the only Cincinnatian crinoid that has a square stem is Xenocrinus baeri, and this is found uniquely in the Liberty Formation, hence giving me the formation of this hash plate as four formations are found at St. Leon. 

 

 

[Tidgy's Dad]

I'm still busy prepping the hash plate, here's the current state of play :

In the last few days I've been focussing on the rhynchonellids. 

There are three species that occur in the four formations found at St.Leon, one of them, Rhynchotrema dentatum is easily recognizable as it has only one plication in the sulcus. Unfortunately, it isn't to be found in my hash plate and the other two rhynchonellids are very difficult to tell apart. 

Generally speaking, Hiscobeccus capax is smaller, at 1 - 2 cm on average, smoother, having less prominent growth lines crossing the plications, and flatter, less rounded and more triangular than Lepidocyclus perlamellosum, which is a bit bigger at 2 to 3 cm on average, has very obvious and abundant growth lines, and is rounder. Trouble is, they are both very variable in their morphology.

 

They look to be smooth, but is this just erosion or sediment infilling? The one on the lower right above, you can see I've etched out some of the growth lines.  

The biggest one below, lying on its side is 2.2 cm across, but the others in the hash are all between one and two cm wide. 

The one at the top in the picture above has also given a bonus (or two). You can maybe just make out at the top right hand edge and the very bottom of the left side a couple of very interesting bryozoans, the same species, but I've no idea what. They consist of an encrusting mat with a rising section in the centre which is 1.5 to 2 mm in diameter. 

Here's the one on the left :

And the one on the right :

One of the rhynchonellids on the reverse of the hash shows much more distinct growth lines but would only have been 1.5 cm wide.

 

 

 

 

[Tidgy's Dad]

Here are some loose specimens of the rhynchonellids : 

The one on the left comes from a piece of matrix that broke off during transit from the USA and then I boshed about to get the valve separated and tidied up a tad.

2 cm across :

The next one, second from left,  also came loose from the main hash plate during postage, 1.8 cm wide but 2 cm high :

The two on the right were found loose at St. Leon, so it's uncertain if they're from the same formation, but they are lovely.

The one on the left is flatter, has a more obvious fold and a less incurved beak. Two species or variations of one? 

 

 

 

 

 

 

 

[Tidgy's Dad]

And the other rounder one on the right. 1.5 cm across.

 

 

 

[FossilNerd]

I really like those rhynchonellids of your’s. Little beauties! 
 

18 hours ago, Tidgy's Dad said:

Two species or variations of one? 

This. This is what gets me. I often don’t go farther than genus on specimen IDs simply because the variations can be so subtle. Is it two species, a variant, or just a younger version of the same species? This is especially true for me on brachiopods. 

 

It can be maddening, but I remind myself that I was lucky to get any ID to phylum a year ago. So I’m getting there. Slowly, but surely!  

[Tidgy's Dad]

3 hours ago, FossilNerd said:

I often don’t go farther than genus on specimen IDs simply because the variations can be so subtle. Is it two species, a variant, or just a younger version of the same species? This is especially true for me on brachiopods. 

Well, I'm a lumper, so I think there are more species than there should be anyway. 

But brachs are often classified by their internal structure, which is fine, but not of a lot of help with rhynchonellids, among other groups, because they have such good articulation that the valves rarely open or separate after death. Cutting them open ruins the specimen and often reveals nothing. 

It's okay, i think I know which ones above are which, but then if I overthink it, i change my mind again. 

Thanks for you comments.  

I'm glad you like these rhynchonellids, and I'm happy too, because I have a section of rhynchonellid evolution in this thread, from Rostricellula through Rhynchotrema to Hiscobeccus and Lepidocyclus. Lovely. 

[RuMert]

Look like our Mosquella (mid-Tithonian)

[FossilNerd]

1 hour ago, Tidgy's Dad said:

...if I overthink it, i change my mind again. 

You said it! Overthinking is probably my biggest problem honestly. 

1 hour ago, Tidgy's Dad said:

I'm glad you like these rhynchonellids, and I'm happy too, because I have a section of rhynchonellid evolution in this thread, from Rostricellula through Rhynchotrema to Hiscobeccus and Lepidocyclus.

That’s great Adam! 

[Wrangellian]

The prepping is looking good, Adam. I love those hash(?)plates, with fat little brachs and bryos. Do you ever apply a bit of acid (vinegar) when you're done, to disguise the white scrape-marks around the shells, or do these pieces not respond well to that treatment? I figure Nature does the same over longer periods of time when the hashplates are exposed to the rain, so it should work, but I've never tried it because I haven't gotten into prepping such things.

I've got one loose brachiopod of that sort from that general area but offhand I'm not sure of the ID or which location it came from as it was a purchase years ago and the data was lost. I should get a pic of it for you.

[Tidgy's Dad]

16 hours ago, RuMert said:

Look like our Mosquella (mid-Tithonian)

Yes, the rhynchonellids are not generally particularly morpholgically very variable, with one or two notable exceptions. They evolved a good body plan and stuck with it. 

Mosquella is a Tetrarhynchiid and thus about as far removed from the original Ordovician families as is possible, but the similarities in external appearance are obvious. 

Mosquella is on my wants list! 

Thank you for looking at my thread. 

[Tidgy's Dad]

12 hours ago, Wrangellian said:

The prepping is looking good, Adam. I love those hash(?)plates, with fat little brachs and bryos. Do you ever apply a bit of acid (vinegar) when you're done, to disguise the white scrape-marks around the shells, or do these pieces not respond well to that treatment? I figure Nature does the same over longer periods of time when the hashplates are exposed to the rain, so it should work, but I've never tried it because I haven't gotten into prepping such things.

I've got one loose brachiopod of that sort from that general area but offhand I'm not sure of the ID or which location it came from as it was a purchase years ago and the data was lost. I should get a pic of it for you.

Thanks, Eric.

Yes, love this hash plate, not just brachys and bryos but crinoid columnals and trilobits too. 

Haven't tried the vinegar on the white scratch areas, doesn't bother me too much, but these shells are easily dissolved in vinegar from a previous test, so i'll leave it. 

Yes, please post your brachiopod when you can, I've been studying the fossils of this region quite extensively so may be able to have a stab at an id. 

[Monica]

Adam - your hash plate looks delicious - great find from Ralph, and great prep work by you!!! 

 

I especially like the Leptaena (I'm assuming that's what they are!) brachiopods