ADAM'S SILURIAN

[Tidgy's Dad]

This one appeared in one of the group photos above. 

It is 1.4 cm long and 5 mm wide maximum, 2.5 mm in the middle of the 'stem'.

Also from the excellent @JohnBrewer

It is rather like a favositid coral in its structure but is much too small and ramose. So I think this is the Trematosome Amplexopora microtoma. From the Wren's Nest.

[Tidgy's Dad]

And this little 'stick' trepostome is quite pretty. 

This was from the quite canny Candace @thelivingdead531and thus from Wren's Nest, Dudley. Thanks, friend! 

There are three species of Asperopora found here, Asperopora aspera, which is the massive form, Asperopora multipora, which is encrusting and Asperopora denispora, which is ramose. 

So, i'm guessing this is..........(1 point for a correct answer). 

Length 10.5 mm, max width 8 mm, stem average width 2.5 mm. 

 

 

 

 

[Tidgy's Dad]

Not all of the ramose bryozoa were tremastomes, this one is a cryptostome (actually, there is a bit of debate!) I think it is Rhombopora mawi, the third most common bryozoan species found at Dudley . Thanks again to the kind Candace @thelivingdead531

It looks very much like Eridotrypa cava, but the zooecia do not have  such a high angle of exit, the 'caves'. It is also much thinner on average, but this specimen appears wider as it is a bit squished. 1.3 cm long, 8 mm wide at the top, stem 3 mm in the middle, though a bit flattened so was probably half of this. 

[ynot]

Getting quite a collection here Adam.

[Tidgy's Dad]

11 hours ago, ynot said:

Getting quite a collection here Adam.

Yup, really have a great number of these Wenlock limestone fossils, a good representative collection, though it was a very rich ecosystem. 

After the rest of the bryozoa, I've still got to post the brachiopods, gastropods, crinoids and trilobites too! 

[ynot]

3 hours ago, Tidgy's Dad said:

e brachiopods, gastropods, crinoids and trilobites too! 

Oh my!

[Tidgy's Dad]

This little bryozoan is also a cryptostome, it's tiny size and the fact there is a handy partial cross-section of one leads me to think this is Pachydictya crassa. 

Which is nice as I have this genus from the Hirnantian (Uppermost Ordovician) of the UK too! Thanks, Candace! @thelivingdead531

The bigger one is 9 mm long and 2 mm wide. 

On the reverse is a very interesting double of a piece of Pachydictya lying immediately under the similar looking but much larger coral Thamnopora cristata. It's a good example of how bryozoa usually have much smaller living chambers than corals. 

[Tidgy's Dad]

The most common bryozoan found in the Wren's Nest is said to be the encrusting cystoporatan Fistulipora nummulina. 

In my own collection, I think this is pretty much true, I have several. 

Here is one, not from Dudley, but from Hobbs Quarry, Longhope, Forest of Dean. It's encrusting the underside of the tabulate coral Thecia expatiata. 

The whole coral, as seen below is 6.5 cm long and 4.9 cm wide. The Fistulipora covering the bottom left quarter about 2.3 cm in diameter. 

Here is a close up :

Fistulipora seems to like the underside of this coral. Here is another example from the Wren's nest this time, on a Thecia kindly given to me by Candace @thelivingdead531 Thanks once more, Candace! 

The whole rock is 1.9 mm long and 1.4 mm at it's widest. 

There are a couple of other nice examples of Fistulipora on the underside of Thecia on the net. But it also encrusts other bryozoa, crinoids and brachiopods. 

Here is one on the bryozoan , Asperopora aspera for example . Total length of the whole specimen (Asperopora)  1.9 cm. This one again from Wren's Nest, again thanks to Candace. 

[thelivingdead531]

I’m so happy that you are still enjoying these, Adam @Tidgy's Dad. Your photography really brings out the details. 

[Tidgy's Dad]

On 11/26/2018 at 11:06 AM, thelivingdead531 said:

I’m so happy that you are still enjoying these, Adam @Tidgy's Dad. Your photography really brings out the details. 

Thank you, Candace, as this next one is also one of the many delightful specimens that you sent me. 

It's  bryozoan that formed mats, encrusting on the sea floor, the cystoporid Favositella interpuncta, as it looks quite like a smaller version of the coral Favosites. 

The specimen is a fragment, 3.4 cm long and 1.8 wide.

It grew on the substrate and here is up to 5 mm deep. Seems to be growing on a substrate which is now just calcite, but was presumably a limey sediment or rock back then.  

[Tidgy's Dad]

Fenestrate bryozoans aren't particularly abundant in the Wenlock, they become more diverse in the Devonian and then a major part of the reef communities in the Carboniferous and Permian. However, a few genera and species do occur, and they can be had to tell apart, as is so often the case with bryozoans unless you have good quality polished sections. 

These ones are from Wren's Nest and were gifted to me by jaunty John, @JohnBrewer

From the general form of the zoarium (or at least the fragments preserved) , the  shape of the zooecia and the fact that each zooarium can be horizontally next to its neighbour rather than diagonal to it, plus the size, I would tentatively suggest these are bits of Archaeofenestella rigidula. 

 

This one's 1.6 cm high.

And this one is 1.5 cm wide : 

[Tidgy's Dad]

That's all the bryozoa I have from the Wren's Nest, Dudley, but I have one more to show from the Wenlock Limestone, this one found at my spot in the South Malvern Hills, Worcestershire. 

It is another fenestellid, Fenestella subantiqua, noted for it's large size and rather more squamous zooecia.( it does not appear at Wren's nest where it is replaced by the smaller F. pseudosubantiqua.) 

Here is the specimen, shown next to the Wren's Nest fenestellids to show the size difference. The actual fossil in the matrix is 1.8 cm long and 1.5 cm wide. (specimen on right) 

Close up :

And closer still:

[Tidgy's Dad]

Sidetracked by older specimens, it's been so long since I've made an entry here! 

And it'll be a while before i continue with my Wenlock material. 

However, just a little graptolite for now, part of a competition win from Guy and Maryse, so thanks @marguy

This is Llandovery age from Chalonnes-Sur-Loire in France. It would appear to be a monograptid, maybe Campograptus lobiferus, but it's not well enough preserved for me to be certain. 

And some little bits on the reverse :

 

[Tidgy's Dad]

Close ups of detail :

[Tidgy's Dad]

Blimey! 

It's been more than 21 months since I last delved into the Wenlock Limestone. Busy with earlier stuff, but now caught up again. 

And my friend John, @JohnBrewer had sent me even more stuff to sort through before then, so I'll be kept busy for a while. 

Notice the two bags of micro-matrix. 

Sorting these was my first task. 

I love sorting through this sort of stuff. 

Full of tiny little things, some identifiable, some needing some prep, some junk, but all good fun.

Here are just the corals and bryozoa that I have managed to separate and have begun to sort :

This should keep me off the streets for a bit. 

 

[Tidgy's Dad]

First up, a nice little bryozoan hash, 2.5 cm across.

[Tidgy's Dad]

An attempt at providing some ids for the most commonly found bryozoa from the British Wenlock Limestone.

Please note that the bryozoan fauna is very different to the equivalent Wenlock age faunas of the Lower Rochester Shale of North America or the Gotland area of Sweden.

1. Fistulipora nummulina. 

The most common bryozoan in the British Wenlock limestone, accounting for 24% of the bryozoan fauna according to Owen 1969, F. nummulina is easily recognized as it is tiny, encrusts other organisms including corals, brachiopods, crinoids and other bryozoa, and has fairly closely packed zooecia, with what appear to be thick walls in between, and are very variable in shape. 

I have posted a few examples further up this page and here are just a few more. I'm sure further examples will be posted clinging to other specimens as this thread continues. 

Once again on Asperopora aspera, another bryozoan, it seems to favour this species and the coral Thecia expatiata in my limited number of specimens. 

Scale in mm. 

  

You can see another little bit of it growing round onto the reverse side. 

And on another specimen of A. aspera. 

This one has come loose from it's host. This is the curves inwards attachment side which seems to indicate it was growing around a curved object with horizontal ridges, maybe a rugose coral or crinoid stem. 

The outer surface:

 

 

 

[FossilDAWG]

Thanks Adam.  This will be very useful when I find the time to sort and ID my Wren's Nest material.

 

Don

[Tidgy's Dad]

19 hours ago, FossilDAWG said:

Thanks Adam.  This will be very useful when I find the time to sort and ID my Wren's Nest material.

 

Don

 

I hope it helps, but I'm not getting carried away. We both know that to properly id bryozoa often requires polished cross-sections and even then it's a specialist field. This is just an attempt to be able to have a chance of getting an id with just a hand lens but I am not claiming it is a definitive guide or infallible, not by any means. 

[Tidgy's Dad]

2. Eridotrypa cava.

Most of the bryozoan species found in the Wenlock limestone are ramose 'stick' bryozoans and are often broken into small sections. Obviously, this is true with the micro-matrix in particular. These stick bryozoans are fragile, suggesting deeper, quieter waters with slow sedimentation.

Eridotrypa cava is the second most commonly found bryozoa accounting for 20% of the bryozoan specimens found. I already posted one on the previous page. 

It is a ramose form with oval to elongated zooecia and the apertures are angled downwards into the zooarium, hence the specific name 'cava'. Sometimes the mesozooecia, smaller openings between the larger autozooecia are obvious, sometimes not. Mesozooecia are immature features that would have developed into adult autozooecia given time.

This species is easily confused with other genera which also have oval or elongate openings, but the angle of exit from the zooarium is the giveaway, as the others have zooecia which go only horizontally into the 'stem'. 

However, as the opening are often filled with sediment, one can't always see the difference, so look for worn or broken areas that show the slant or try to find a zooecium that you can prep. Prepping is very difficult as these are tiny and the zooecial walls are quite fragile. 

Some examples :

Wear on the specimen shows the elongated zooecia running under the eroded wall of the zooarium. 

Here the mesozooecia are quite obvious.

 

 

 

 

[Tidgy's Dad]

3. Rhombopora mawi.

 

At first, I was beginning to wonder where these were. The third most common bryozoan species representing 14% of the specimens found. That means that the three top species represent 58% of the bryozoan fauna between them. So a lot of what you find will be these three. 

But where were mine? 

Rhombopora with its oval; sometimes slightly squared off zooecia, arranged neatly in rows and diagonal patterns is very distinctive. The reason is that the species in the British Wenlock are R. mawi and it is tiny, with the zooaria being ramose but with the stems only 1 to 1.5 mm in diameter at the most! So, they are very fragile and you won't find many in the micro-matrix, but check your rock pieces and hash plates and you'll find loads of them. 

On a very small crinoid columnal :

[Tidgy's Dad]

4. Hallopora elegantula. 

 

Hallopora elegantula constitutes 5% of the bryozoan fauna in the British Wenlock Limestone. 

This is one of the few species that is also found in the equivalent Lower Rochester Shale of North America where it accounts for 16% of the fossil bryozoans. 

Hallopora also accounts for 15% of the Swedish Gotland bryozoans, but not the same species. 

In eroded matrix there seems to be a lot more than just 5%, because these are a lot more robust than most of the other species and are rather noticeable and pretty as you can see the zooecia even with the naked eye. So, I think preservation and collecting bias come into play. 

Although this is another ramose form, the zoarium can be very variable in the width of stems or branches and the shape of the base and junctions of branches. 

The zooecia are usually rounded, but may be sub-rounded or even polygonal when they grow closely together. They are also very large compared to most other bryozoan zooecia, comparable to some of the openings in smaller 'stick' tabulate corals. But these have mesozooids in between them. 

Here is a group of specimens showing the scale in mm : 

And an H. elegantula, on the left, next to a bryozoan with more 'standard' sized zooecia.

Sometimes, you can see a small central 'pillar':

A cross-section :

A specimen covered in the similar looking, but with much smaller zooecia, encrusting bryozoan Asperopora multispora. 

 

This side is almost completely covered :

Some internal structure : 

Another one with an encrusting bryozoan on it :  

 

 

 

[TqB]

It's a lovely bryozoan! What would you say is the largest zooecial diameter? - as you know, the question of the crossover size between bryozoan/tabulate/chaetetid is always coming up.

[Tidgy's Dad]

6 hours ago, TqB said:

It's a lovely bryozoan! What would you say is the largest zooecial diameter? - as you know, the question of the crossover size between bryozoan/tabulate/chaetetid is always coming up.

Yes, they're rather lovely. 

The maximum diameter is over 0.5 mm, I'd say, but I'm rather ashamed to say I have nothing for accurate measurement.

The only chaetetid I have from the Wenlock is Solenopora filiformis .

The apertures are really tiny :

Hallopora compared to the ramose tabulate coral Thamnopora cristata : 

And to the encrusting or massive tabulate Thecia expatia :

And the odd tabulate Coenites juniperus : 

Perhaps most similar to Coenites seriatopora :

But the organized lines of the tabulate corallites and its lack of mesozooids are the giveaways. 

[TqB]

Thank you! That's very helpful, and confirms the usual advice that 0.5-1.0 is generally the awkward range, apart from some odd but identifiable small tabulates.