ADAM'S SILURIAN

[Tidgy's Dad]

17. Pachydictya crassa.

 

Bifoliate cryptostome bryozoans are quite rare in the Much Wenlock Limestone Formation and include Pachydictya crassa and Ptilodictya lanceolata. In total bifoliate cryprostomata account for less than 1% of the bryozoan fauna. 

Pachydictya crassa can be ribbon like to sub-rounded and is a branching form. It is very small, the stems are only a mm or so in diameter. Oval apertures.

Here are a couple : 

[Tidgy's Dad]

18. Ptilodictya lanceolata. 

 

The other bifoliate cryptostome is Ptilodictya lanceolata, which is a really beautiful, curved bryozoan when complete, but all I have are fragments which is apparently usually the case, as with most of the bryozoans in the Wenlock Limestone. It's actually got a ridge running along one side, so is sort of triangular in cross-section. Ptilodictya lanceolata is also the only bryozoan that can also be found in the equivalent Wenlock strata of Gotland, Sweden. 

You usually can't actually make out the zooecia without a very powerful microscope, but the rows of bumps, which are not acanthpores, are very distictive. 

 

 

 

 

 

 

[Tidgy's Dad]

19. Meekopora dudleyensis.

 

I had one of these incorrectly labelled as a coral a couple of years ago in this thread. I had it listed as Trachypora seelyi, but it's much too big among other differences. I have learned a lot since I started this thread, and I'm sure I'll have recognized further errors in a couple more years time! 

Meekopora dudleyensis is a bifoliate cystoporid. It can be strap-shaped or leaf-like and has small circular maculae (holes that look like corallites but are actually formed of cystpores) The zooarium has lots of smaller apertures surrounding these and leading away and each of these is itself surrounded by even smaller cystopores. They can be quite variable but I think they are the most beautiful of the Much Wenlock Limestone bryozoa. 

The larger maculae and the smaller multiple zooecia can be clearly seen.

 

The close ups reveal tiny cystopores between the zooecia. I had no idea they were even there until I got the specimen under the microscope. 

Another specimen : 

This one's much more like Fistuliopora (same family). 

And this one's very similar to the coral, Aulopora, but I think you can still see the zooecia :

 

[Tidgy's Dad]

20. Nicholsonella parva.

 

Another bifoliate/frondose  species, Nicholsonella parva is a trepostome which used to be assigned to a family and suborder but has now been removed and is an 'unassigned' genus. It's pretty unusual. The zooecia are quite thick walled and separated by large polgonal mesozooids. It has styles which is the modern name for the acanthopores, or the spine bases that form hollows in the surface of the zooarium but are rarely preserved. The specimen is 3 cm tall. It is found at the Wren's Nest, but I don't have any from there, this one is from a road cut in the South Malvern Hills in Worcestershire from my collecting days there 35 years ago! I had it wrongly identified as Hallopora elegantula even posting it as such earlier in this thread, but now I've got my microscope and more information, it clearly isn't. 

Here is the complete zooarium :

 

You can see how little detail can be seen in hand sample. 

The other side. I haven't fully prepped this one.

The top view showing the flattened, frondose shape.

A different angle showing a growth bulge on one side.

And the amount of detail I couldn't see before that is revealed with the microscope is amazing.

The white circles are the zooecia, surrounded by the large grey polygonal mesozooids and with the occasional black spot which are the styles.  

Another section, lower down on the zooarium, showing comparatively few zooecia and a huge amount of mesozooids. 

[Tidgy's Dad]

21a. Monotrypa macropora.

22b. Monotrypa paterella. 

 

Monotrypa macropora has comparatively large zooecia, as the name suggests. It has a domed zooarium which is often concavo-convex as it begins its growth on a coral or brachiopod. They can be quite small but grow up to 15 cm across. The zooecia are polygonal, thin-walled and adjacent with no spaces, styles or mesozooecia present. This gives it a look similar to a favositid coral, but in cross-section it is thinly layered. 

Monotrypa paterella (was M. patera) is smaller with the zooarium being a button-shaped disc only 1 to 2 cm in diameter and 1 to 2 mm thick. It has much smaller polygonal, adjacent zooecia. 

I don't know if I have any of these at all, but these could be M. macropora, the top layer of Favosites sp. Dunno.The apertures are up to 5mm wide in this top one, so probably favositid?

These are much smaller, apertures 1 to 2 mm wide, so maybe Monotrypa? 

These lumpy ones I thought were M. paterella but i wouldn't call them button-shaped and the openings are not very clear but don't seem to be polygonal and adjacent, so not sure what these are either! 5 mm or so diameter , this first one on a favositid coral, I think. 

Another :

This maybe just something else a bit eroded.

Bit blurry this one. Sorry.

Possible.

 

 

 

[Tidgy's Dad]

There are many other bryozoans that occur in the Much Wenlock Limestone Formation.

Mitoclema sp. is a tiny tubular form with tubular zooaria raised in a spiral around the stem. 

Glauconomella looks like feathers and is very beautiful.

Pseudohornera resembles a dendroid graptolite.

There are also several that are encrusting on brachiopods; Corynotrypa, Lichenalia, and Sagenella. 

I haven't found any of these, but as I haven't fully prepped most of my brachiopods yet, I'm hopeful I may find at least some of the above later. 

For now, here are some small fragments and weird things that may be unidentified bryozoa. Some of them, I think I might be able to fit into species I've already covered, but I'm not certain. Others I have no idea. 

This one makes me think Lichenaria, but it's too big and not encrusting on a brachiopod, as far as I can tell.

 

This one, bottom left, looks like Mitoclema, but I thought they were single tubes, not branching:

No idea, but it's very pretty :

This looks like a very weird fenestellid :

 

 

 

[Tidgy's Dad]

I don't have any specimens from the equivalent age formations of the Niagaran of North America, but I do have a few pieces from  Gotland in Sweden thanks to the wonderful @Kasia

This hash is from the coast near Irevik, Gotland and is a nice piece of crinoidal limesone. The crinoids are represented by isolated columnals and sometimes quite long sections of stem, but further identification is not possible as there are about 200 species belonging to more than fifty genera. It is probably from the Visby Beds. There are also fragments of large brachiopods and tabulate corals; you can a really nice specimen of the small mound coral Favosites favosus quite clearly. The whole rock is 15 cm long and the longest crinoid stem section about 2 cm.

If you look very closely you can also see some rather thin stick bryozoans up to a centimetre in length and 0.5 to 1.5 mm wide. 

The Gotland bryozoan fauna is very different from that of the British Wenlock Limestone Formation. It is odd as many of the corals, brachiopods and other fauna are shared. It has been suggested that free-swimming bryozoan larvae don't travel as far as other animal groups larvae. 

The most common species, making up 26% of the Gotland bryozoan fauna, is Helopora lindstromi, a cryptostome. (Nothing to do with Hallopora, lots of bryozoa have confusingly similar names.) It has well spaced zooecia arranged in rows entering the zooarium at an angle and contained in little tubes that stick out. Here are some from the hash plate shown above : 

This one has a another smaller, unidentified species just below it.

And from the reverse of the same piece of rock :

[Tidgy's Dad]

This piece is packed full of ramose tabulate corals. It is from the small island of Faro, just north-east of the main isle of Gotland. The rock is 10 cm at it's widest.

The longest coral is 4.5 cm.

The reverse :

In this piece too are little Helopora lindstromi.

 

 

[Tidgy's Dad]

The second most common bryozoan, representing 22% of the bryozoan fauna of the Gotland Wenlock is Phaenopora lindstromi, another cryptostome. Small and well separated zooecia. It's very interesting that the Wenlock of the UK is dominated by ramose trepostomes and encrusting bryozoa, but here cryptostomes seem to dominate.  

This one's from the first piece of rock from Gotland shown a couple of posts above. About 1.5 cm long. But it's not too well preserved so I'm not certain as to the id.

So this species and Helopora lindstromi account for almost half of all the bryozoans found in the Gotland Wenlock. 

 

[Tidgy's Dad]

The trepostomes found in Gotland are poorly preserved, show little detail and cannot be identified to species level. The genera Hallopora ( 15% of the bryozoan fauna) and Eridotrypa ( 8%) are the most common, but ,though they can't be allocated to a species, it is clear that they are not the species found in the British Wenlock. There is a theory that the environment here was ideally suited to cryptostomes , but the trepostomes grew nearby and were washed in during sedimentation explaining their poor preservation. Some of the more rough looking unidentified specimens in the above photos could be trepostomes as could these ones (nice crinoid ossicles) :

And this, or could it be a coral? 

 

[Tidgy's Dad]

Of the other Gotland bryozoa, the encrusting Fistulipora mutabilis accounts for 16% of the bryozoans found. It seems to be the equivalent of F. nummulina in the UK. 

Then there is Ptilodictya lanceolata, also found in the UK which makes up 6% of the bryozoa.

And another encruster, Crepipora lunariata. (3%) 

All the other species comprise only 4% of the bryozoans in the Gotland Wenlock reef and include Berenicea consimilis which is the only species said to occur in the UK, Sweden and North America but is very rare, has not been properly studied and seems to actually proably be three different species. Also included in the 4% are the fenestrates which are usually only fragmentary. Here are a couple from my big hash from Irevik, Gotland.

[Tidgy's Dad]

Sometimes tabulate corals or sponges can be mistaken for bryozoans. 

Even small favositids, like the Favosites favosus from my hash plate from Irevik, Gotland, have apertures too big to be bryozoans. 

Here's a close up of the one shown above. The corallites are up to 2 mm across, much smaller than some other  corals, but bigger than bryozoan zooecia. The colony is 2.3 cm across. 

Even closer : 

The corallites from the side. 

 

 

[Tidgy's Dad]

Coenites has to be one of the most difficult genera to distinguish as coral rather than bryozoa. Indeed several palaeontologists even quite recently have written papers to show that it is a bryozoan. But most still classify it as a tabulate coral, so that is where I put it for now. It is a ramose form with corallites  not much, if at all, bigger than than the zooecia of some bryozoa. 

The rock from Faro, the little island north-east of Gotland, Sweden,  shown a few posts above is largely composed of a mass of Coenites repens, the longer pieces being 4.5cm long. The diameter of the zooarium is from 2 to 7 mm.The corallites are less than a millimetre in diameter but still just about visible to the naked eye and bigger than most bryozoan zooecia. 

Here are some close ups, this first one seems to have a bit of paint on it : 

You can see a broken end here that looks more like a rugose coral or a bryzoan and is part of the argument of Brood in 1970 to propose the genus as a bryozoan. 

But you can also see a fairly standard bryozoan to the right centre of the photo which is much smaller. 

The next one is from the reverse of the same block. 

Here is a specimen of Coenites repens from another piece of rock from Faro. Also present is a Favosites favosus and some much smaller bryozoa. Hmmmm. Bit blurred, sorry: 

And this is a less well preserved specimen from my hash plate from Irevik, Gotland :

Here we see some specimens of Coenites repens and a heliolitid coral from my Irevik hash plate. Notice the stellate and rather large corallites of the heliolitid. 

 

 

 

 

 

 

 

[Tidgy's Dad]

At the Wren's Nest, Dudley, there are two other species of Coenites commonly found,  indeed they are among the most common finds in the loose matrix and hash pieces. Yet, I never found any at the other Wenlock Limestone sites I visited, so that's interesting. 

Here is Coenites seriatopora, notice the very much arranged linear pattern of the corallites and the large size compared to bryozoan zooecia. 

 

Hmmm.

Perhaps I've gone a bit overboard with pictures od this species, but i do think they're very pretty. 

 

 

 

[Tidgy's Dad]

I've already posted Coenites juniperinus but here are some more from the last batch of matrix I received from my friend @JohnBrewer I love these, they are instantly recognizable by their rather weird shaped corallite openings. 

 

Sometimes they are only small fragments : 

Or longer pieces : 

 

[Tidgy's Dad]

I think these three bits from the Wren's Nest matrix are bits of the ramose favositid Thamnopora cristata. Again they have large corallites to differentiate them from some similar looking bryozoans.

 

 

[Tidgy's Dad]

Perhaps the most troublesome of this type of fossil found at the Wren's Nest is Trachypora (?) seeleyi. Firstly, the genus is otherwise not known until the Devonian and also is often now referred to as Thamnoptychia, but not always.  It has traditionally been regarded as a favositid tabulate coral, but based on internal structure some have argues it's a heliolitid. Still others suggest that because of it's tiny size and the lack of proper studies carried out, it may well be a bryozoan.

It certainly is very small, the zooarium only a mm or so across, so the corallites / zooecia are really miniscule. But the later Devonian species are very similar. The exception that tests the rule?  

At least it is quite distinctive and easy to tell apart from other species. It is the long, thin, branching specimen with oval apertures in the middle left of this photo.

Here is another specimen in close up. Compare the size with a Favosites sp. and a fenestellid. 

This one has more rounded apertures and I think could be something else entirely. 

Not sure about this odd thing either.

[Tidgy's Dad]

 On her marvelous trip to Sweden, @Kasia collected some specimens from the beach at Djupvik, Gotland and kindly sent a few specimens to me. They are a bit water worn, but still rather nice to have.  Probably from the Slite Formation. 

Here is a nice colony of Favosites sp. Several species can be found in the Gotland Wenlock of Sweden, and I can't tell them apart, to be frank. 

You can see some of the calcite crystals sparkling as they catch the light. Very pretty.

Nice details of the tabulae and other details on the underside :

Here is an attractive slice of another Favosites sp. 

 

[Tidgy's Dad]

Also from Djupvik is this heliolitid. Could be Heliolites, Propora or Plasmopora, all occur in the Gotland Wenlock but I don't think there's enough detail here to be certain of the genus.

 

[Tidgy's Dad]

This one is also a Djupvik find. 

It may not be a terribly impressive example, but it's rather special to me, as despite being one of the more famous fossils from the Wenlock, I failed to find any during my own collecting trips in the Wenlock limestone and I didn't get any from Candace or John either, so it is great to finally have a specimen of the chain coral Halysites. 

This one's probably Halysites catenularius. 

It runs all through the rock in all directions. 

So, an extra special thanks for this one @Kasia

[Tidgy's Dad]

Finally from the Wenlock of Djupvik, Gotland is this rugose horn coral. I don't think any further id is possible, though one day I might try to polish an end.

 

[Tidgy's Dad]

And the final coral from my Wenlock collection is this tiny rugose specimen from the Wren's Nest, Dudley. 

I don't think any adult species from this location were this small, so it's a juvenile, but which species is not possible for me to guess at.

Scale's a bit blurred, but it's 4 mm tall. 

Next up : Brachiopods !

 

[Tidgy's Dad]

The Wenlock Limestone Formation is Homerian in age, which is the Upper part of the Middle Silurian. It can achieve a thickness of up 29 metres (95 feet). 

In the UK, the Sheinwoodian is the lower section of the Wenlock  and represented by the shales, marls, mudstones and limestones of what used to be known as the Wenlock Shales, but is now split into separate formations. This series can be considerably thicker than the Limestones with a thickness of up to 292 metres (960 feet). Much of it is non or sparsely fossiliferous, but parts of the grey green mudstones and shales of the Buildwas Formation can be very productive.  It is 72 to 131 feet thick. 

The discinids are a very interesting group of inarticulate brachiopods. They are a family within the order Lingulida and like their cousins from the family Lingulidae and the unrelated craniids have a comparatively simple design that has survived little changed to the present day. I find it fascinating that many of the more 'advanced' groups of articulate brachiopod achieved such success and diversity, dominated the sea floors and then became extinct while these inarticulate groups were not particularly dominant, numerous or diverse after the Cambrian, but still exist today. If it ain't broke, don't fix it; they fit their little niches very well and haven't been forced to change much. Wonderful. 

Anyway, this is Schizotreta walkeri from the Buildwas River Section, Buildwas, Salop (now known as Shropshire) of the Welsh Borderlands, UK. This is the dorsal valve, is 9 mm long, which is about as big as this species gets, and I collected it on one of my trips 35 years ago.  

[Tidgy's Dad]

There are three recognized subphyla of brachiopods, the majority and all the species that follow after this post belong to the Rhynchonelliformea. The Liguliformea are represented in my Wenlock collection by Schizotreta as shown in the post above. The third subphylum is Craniiformea and the order Craniida is still extant today. Petrocrania scabiosa commonly found affixed to Rafinesquina sp. brachiopods in the Upper Ordovician of the North Eastern USA is an example.  

This specimen is from the Order Craniopsida which were at their peak in the Middle Silurian, but declined thereafter, finally becoming extinct in the Early Carboniferous. 

Craniops implicata which looks a little like Schizotreta but is much smaller and far more conical in shape. From the Wren's Nest, Dudley. 

[Tidgy's Dad]

INTERLUDE 

 

While I was checking over various chunks of Wenlock Limestone to see how many brachiopods I could locate, I found this lump, from the Wren's Nest, given to me by @JohnBrewer
I thought it was nothing in particular, just a piece of rock with a few bits of little bryozoan and brachiopod shell fragments on it, but nothing noteworthy. But while giving it a closer examination, I realized the whole rock was a fossil! 

It's a chunk of the stromatoproid Clathrodictyon. 

It was the section towards the bottom right that ignited my suspicions.

The reverse which seems to show astrorhiza / mammelons (raised lumps) and pores. 

The side, showing laminae and pillars, but difficult to see with the naked eye:

The top surface under a microscope :

Pores :

And the reverse side, which may actually be the top, notice the mammelons with openings like craters in the middle of some :

And some views of the sides :

More mammelons visible here, but I think the black dots are mineralogical : 

Not sure what this is:

This is either an epibiont bryozoan colony or a Craniops brachiopod covered in an encrusting bryozoan. I think.