Adam's Ordovician.

[Tidgy's Dad]

On 10/2/2021 at 5:19 AM, doushantuo said:

e.g.:

Indeed. 

Hi, Ben, long time no see. Hope you're well. 

[doushantuo]

THX,ADAM.

Health could be better,truth be told

[Tidgy's Dad]

7 hours ago, doushantuo said:

THX,ADAM.

Health could be better,truth be told

Sorry to hear that.

Take care and :

 

[Tidgy's Dad]

Some more crinoid stem bits from the Late Ordovician of Rattvik, Sweden, including some bigger than the ones I had previously, 

These came from the Sara the World Travelling Ceratopsian overburden and I'm pretty sure are down to our wonderful Forum Friend @Kasia

 

[Kasia]

They do indeed

[Tidgy's Dad]

Some brachiopods from the Platteville Formation of Fennimore, Wisconsin, now. 

These are all from the family Strophomenidae and were sent to my by the ever kind, helpful, knowledgeable and thoughtful Mike @minnbuckeye.

Indeed, the specimens in the several posts that follow with brachiopods from Decorah and Eldorado, Iowa are also courtesy of Mike. 

Thank you, my friend. 

The big one on the top right is a pedicle valve interior of Strophomena plattinensis.

I was desperate for an example of this species and when Mike heard that Tidgy and I were prepared to sell wifey in order to purchase one, he leapt into action and sent a package to me forthwith. wifey is very grateful. 

Notice the large size, remains of the diamond shaped muscle attachment area and comparative flatness of the valve with a slight, gentle dip down toward the anterior. Remember that this is the ventral valve interior as the valve was concave:

Anterior view (above) and posterior view (below) showing the low, flat shell and the slight curve down to the anterior:

Where the outer layer of shell is missing you can see the pseudopunctate shell structure:

 

 

 

[Tidgy's Dad]

The other three are smaller, more domed and the angle of dip towards the anterior is more gentle. 

These are Oepikina minnesotensis. The first one is a complete specimen!

Cleaned up a little:

The concave valve was full of matrix and I couldn't quite get it cleared completely as some of the gloop was pretty resistant. 

Note the 'chevron' pattern on the hinge line which are transmuscle septa. 

And on the other valve:

Very fine parvicostellate ribbing. 

The other two specimens show the interior of the pedicle valve, which is new to my collection.

Notice the large, crenulate teeth and lack of a heart or diamond shaped muscle attachment region :

Lots of little bumps created by the pseudopunctate nature of the interior shell layers.

The pedicle interior of the other specimen: 

Looks like there's a rather lovely and quite large ostracod next to it as well! 

More fan-shaped, unenclosed muscle attachment area:

 

 

 

Edited August 28, 2022 by Tidgy's Dad

[Tidgy's Dad]

Here's the ostracod; Eoleperditia fabulites.

Probably the Mifflin Member of the Platteville Formation. 

[Denis Arcand]

10 hours ago, Tidgy's Dad said:

Here's the ostracod; Eoleperditia fabulites

 

A Class of Crustaceans, Tiny shrimp-like animals live in clam-like shells; the fossil record’s most common arthropods

 

I didn't know that it existed in the Ordovician 

 

Thanks, I just learn something new

 

 

Edited August 30, 2022 by Denis Arcand

[minnbuckeye]

12 minutes ago, Denis Arcand said:

I didn't know that it existed in the Ordovician 

 

@Denis Arcand, the Ordovician Platteville I love to collect from is LOADED with ostrocods. They may outnumber even the brachiopods in number in selected areas.

[Denis Arcand]

2 hours ago, minnbuckeye said:

2 hours ago, Denis Arcand said:

I didn't know that it existed in the Ordovician 

 

@Denis Arcand, the Ordovician Platteville I love to collect from is LOADED with ostrocods. They may outnumber even the brachiopods in number in selected areas.

 

It look like a fun place to collect 

[Tidgy's Dad]

On 8/30/2022 at 2:22 PM, Denis Arcand said:

 

I didn't know that it existed in the Ordovician 

Yes, Ordovician to Recent. Ostracods may have had a Cambrian origin, but most, if not all, of the supposed Cambrian specimens have now been assigned to a separate and quite different class; the Phosphatocopida which became extinct before the end of the Cambrian, so the ostracods are sort of a successor group. 

Here's a phosphatocopid Falites fala from the Late Cambrian of Sweden.

It's the larger knobby thing near the bottom of the photo, just left of centre and is 2mm wide. 

 

Edited August 31, 2022 by Tidgy's Dad

[Tidgy's Dad]

Getting back to the Ordovician, the next two specimens come from the Galena Limestone, Galena Group of Decorah, Iowa. 

I'm not sure which formation. Dubuque? 

This one on the left is Dinorthis meedsi, often listed online by its old name Plaesiomys meedsi. It still belongs to the subfamily Plaesiomyinae, though. 

 

[Tidgy's Dad]

And this is Strophomena trilobata., It looks more like the Platteville  Oepikina specimens shown above than the Strophomena. 

But if we could see the internal structures it would reveal the characteristic diamond or heart shaped muscle attachment area. 

Profile showing the sudden drop off and high domed shell:  

Anterior view:

It is covered in very fine striae:

Nice couple of additions to my Galena Group fossils and material from Decorah, Iowa. . 

 

Edited September 4, 2022 by Tidgy's Dad

[Tidgy's Dad]

Now for a nice selection of brachiopods from the Maquoketa Formation, Elgin Member of Eldorado, Iowa. 

I'm very happy with these, as before this, I only had two brachiopod species from the Maquoketa, plus an couple of trilobits and a pair of Isorthoceras, so this is great. 

Firstly, a few orthids:

As is so often the case, many of the species of orthid in this formation are quite similar in appearance and quite often difficult to tell apart. 

This first large one, top left in the photo above, is Glyptorthis bellarugosa. 

It all gets a bit confusing as there is another species of Glyptorthis present that was known as Hebertella insculpta, was then changed to Hebertella insculpta maquoketensis , then became Glyptorthis insculpta maquoketensis and finally Glyptorthis maquoketensis. 

See here for details :

Glyptorthis.pdf

Notice the pointy beak.

The cross-hatching / reticulate ornamentation diagnostic of the genus is fainter on this species than G. insculpta, and my specimen is a bit glooped up, but you can see it is present:

 

Edited September 7, 2022 by Tidgy's Dad

[Tidgy's Dad]

This one is Plaesiomys occidentalis. Medium sized but they can get quite a bit bigger. 

The species has gone through several name changes over the years, most recently it was known as P. subquadratus occidentalis, but Wright and Stigail elevated the subspecies to species level in 2013. 

Notice the the sub-quadrate shape and fine striae. 

  

Here one can see that the species is convexo-concave, though the brachial valve rises towards the umbo:

There is a second species of Plaesiomys present in the Maquoketa Formation of Iowa. 

P. proavitus is smaller and has fewer and broader ribs.  

[Tidgy's Dad]

Another orthid from the Elgin Member of the Maquoketa Formation of Iowa is Onniella quadrata, sometimes listed as O. porrecta in older literature. 

These are very small, though the species can grow to over 1.5 cm wide.

This is the pedicle valve which has a quite sharp fold running the length of the shell, though it doesn't show up too clearly in the first couple of photos. 

 

The articulation 'teeth':

You can see the fold more clearly here:

The smaller specimen has both valves intact:

Look what pin prepping has done to my thumb! 

 

Notice the 'V' shape in the commissure due to the fold and sulcus. The very similar looking species Diceromyonia ignota that is found in this formation has an almost flat commissure as the fold and sulcus become weak just before the anterior margin.  

 

[Tidgy's Dad]

Before I leave my orthids from the Maquoketa Formation, I'll quickly post a species I received a while back from the still much missed Doren. (caldigger). 

Paucicrura corpulenta is very common in the Maquoketa of Minnesota but extremely rare in Iowa. In Iowa the species is replaced by P. rogata. 

For more pictures, please see two thirds of the way down page 11 of this thread. 

Paucicrura is more rounded than Onniella quadrata, larger, has a less obvious ridge to the fold and a flat commissure.  

 

N.B. Several other orthids occur in the Maquoketa formation which i have not mentioned. 

 

[Tidgy's Dad]

The Maquoketa Formation, In common with most Late Ordovician marine deposits, has a brachiopod fauna dominated by orthids and strophomenids. 

But there is nearly always a species of rhynchonellid or two lurking about. 

There seems to be tendency to identify all the rhynchonellids from the Maquoketa as Hiscobeccus capax ( was Rhynchotrema capax and then Lepidocyclus capax before its current designation.) But there are three common species of rhynchonellid found in the formation. The trouble is they are all from the same subfamily and very similar in many regards, both externally and internally. 

Hiscobeccus capax is large, globose and criss-crossed by notable growth lines. 

Hypsiptycha (Rhynchotrema) anticostiense  is smaller, flatter and with less prominent zigzag lamellae. It also has a more extended beak. 

Rhynchotrema iowense is also small and flat, but has very weak lamellae and a tucked in, blunt beak. It is also more transversely subelliptical. 

The trouble is that juvenile H. capax can resemble either of the other two, externally at least. 

So I think this one is a nicely flying Rhychotrema iowense. But could be a young Hiscobeccus, though brachiopods grow to adult size very quickly, they were, like me, young once. 

[Tidgy's Dad]

Now for some Maquoketa Formation strophomenids.

The smallest one is Eochonetes recedens. 

This one has gone through an awful lot of name changes. 

Leptaena recedens, to Plectambonites recedens, then Thaerodonta recedens, next was Eoplectodonta recedens before returning to Thaerodonta recedens until it was finally placed in Eochonetes in 2016. The other species of sowerbyellid listed for the Maquoketa, Eoplectodonta saxea went through similar name changes before being synonymized with Eochonetes recedens. Phew. 

Note that Eochonetes is not a chonetid, but that it is the genus that is considered to be ancestral to chonetids and therefore to the productids.

Convex brachial valve but showing interarea caused by overhanging pedicle valve. 

Detail of brachial valve, interarea on pedicle valve and pedicle opening. 

Very fine lamellae;

 

Concave pedicle valve:

Weird profile:

Anterior view:

N.B. There is a species of Leptaena found in these beds; Leptaena raymondi. 

 

 

 

 

 

 

 

Edited September 19, 2022 by Tidgy's Dad

[Tidgy's Dad]

There are a few different species of Strophomena present in the Elgin Member of the Maquoketa. 

Mostly, they are slightly to very triangular in appearance and are nasute, which means having a long snout. This refers to a finger like extension on the centre of the anterior margin of the shell. Indeed, Strophomena fluctuosa had such a huge 'nose' that a new genus, Nasutimena was created for it. 

Strophomena fluctuosa occidentalis was a subspecies that was much less triangular and nasute, so it was afforded species status by Wang 1949. But it has remained in the original genus, so this is Strophomena occidentalis. 

The 'noses' often break off or become eroded, but I think there is some evidence of it here. 

Note the slightly triangular shape:

Quite low domed:

Perhaps a little nasute at the anterior end and at the hinge you can see a little of the interarea where the concave pedicle valve overhangs this convex brachia valve. 

Also, the abundance of very fine striae are clear: 

Part of the 'nose' extending beyond what would be the usual edge of the anterior margin: 

Hinge detail visible through the shell, also the pseudopunctate nature of the shell is revealed where it's a bit worn:

Details of the pseudopunctae: 

And striae on a less worn piece of shell:

The overlap of the pedicle valve;

Lateral view:

 

 

[Tidgy's Dad]

I've posted this one earlier in the thread, but now seems a god time to repost it so I have all my Maquoketa Formation specimens together and this belongs to the family Strophomenidae, though a different subfamily. 

This is Megamyonia unicostata from Spring Valley, Minnesota. 

It is 1.9 cm wide a the hingeline. 

[Tidgy's Dad]

The last brachiopod that I have from the Elgin Member of the Maquoketa Formation in Parsons, Tennessee is this Rafinesquina deltoidea. 

R. nutans and R. trentonensis also occur here, but the former has a notable 'nose / tongue' in the centre of the anterior and the latter is flatter with more secondary costae.   

This specimen was broken and glued together when it arrived, (easily done, I know from experience!) so originally I decided not to prep it, but then couldn't resist. These photos are pre-prep, but the post-prep isn't much different so I haven't bothered with new photos.

[Tidgy's Dad]

One couldn't have failed to notice the crinoid holdfasts on the specimen of Rafinesquina shown above. 

These are Lichenocrinus minutus, though the actual species of crinoid they belonged to is unknown though a disparid such as a heterocrinid has been suggested. Lichenocrinus is just a catch all name for holdfasts whose owners are unidentified. 

And a tiny one :

So a huge thank you to my friend Mike, @minnbuckeye for his generosity in helping me to build up my Elgin member, Maquoketa collection as shown in most of the last several posts. 

Marvelous.  

Edited October 8, 2022 by Tidgy's Dad

[Tidgy's Dad]

For my birthday wifey gave me this Ogygiocarella debuchii to replace an O. angustissima I found near Builth Wells in Wales forty years ago but is no longer in my collection. 

This specimen is Middle Ordovician, Llandeilo Group; Middleton Series, Abereiddion Stage, Meadowtown Formation (was the Meadowtown Beds). 

Location : Lower Wood Brook, Meadowtown, Shropshire, England.

 

This species is said by some to be the first trilobite to be described in a scientific publication.

The Welsh Rev. Edward Lhwyd  published a lovely drawing of it in "The Philosophical Transactions of The Royal Society" all the way back in 1698, in a letter "Concerning Several Regularly Figured Stones Lately Found by Him". He described it as "the skeleton of some flat Fish........"

He seemingly found it near Llandeilo, likely on the estate of Lord Dynefor. 

Wonderful, and you can see the resemblance to a plaice or other flatfish.