Middle Devonian Stromatoporoids, Belgium

[EmileC]

I have assembled quite the collection of stromatoporoid fossils in the last year and a half since I began this hobby. They are my 'main focus' for now, together with brachiopods and corals to a lesser extent (especially Gypidulid Brachiopods). I have been reading scientific papers on stromatoporoids for a few days because I hope to get a full understanding of them. The articles were mainly by Stephen Kershaw and collaborators and by the late Colin Stearn who have both produced some great stromatoporoid literature.

 

I am currently reading https://journals.ku.edu/treatiseonline/article/view/4088/3855 (Internal morphology of the Paleozoic Stromatoporoidea by Stearn 2015) in order to identify my fossils. I have found it a good tool but I'm having a hard time distinguishing between pillars and pachysteles and between laminae and pachystromes. I understand pachysteles and pachystromes are thicker and more robust versions of their counterparts, but the problem is that the figures provided in the paper don't have a scale (only magnification is mentioned) and it subsequently becomes very hard to distinguish. I have also not found any other clear illustrations of the difference on the internet.

Here's a useful table by Stearn for determining the type of stromatoporoid:

 

cyst plates and pillars (Labechiida)

laminae and pillars (Clathrodictyida, Stromatoporellida)

pillars and colliculi (Actinostromatida)

pachysteles and pachystromes in an amalgamate structure (Stromatoporida, Syringostromatida)

 

My questions are:

1. Does anyone know a useful way to determine genus/family other than what I'm doing?
2. Is there any particular way to distinguish pachystromes and pachysteles from laminae and pillars other than looking at their robustness? 
3. If anyone has some interesting literature about this, please tell me about it.

 

I have provided close-up pictures of an example specimen below (I have dozens more, so I'm able to provide them if necessary). Is anyone able to say if it is composed of laminae and pillars, pachystromes and pachsteles or any combination thereof (maybe also cyst plates)?

Also, I assume all my specimens are the same genus because:

1. They were all found at the same locality in the same formation (Middle to Upper Hanonet fm.)
2. Stromatoporoid assemblages typically have low species diversity, having one genus more abundant than others ( as stated in Kerschaw 1990; Da Silva, Kershaw, Boulvain 2011)

I will look at every specimen before assigning it a genus/species though, just to be sure.

 

There's also a question I have about why there are less stromatoporoid fossils in units 1 and 2 of Hanonet fm relative to the later units (at least in my experience). They are more abundant where there are argillaceous limestones than where there are calcareous shales. I know stromatoporoids preferred to grow on carbonate substrates so it might be because there's simply more carbon in the limestones. Then there's the question of why the shales are followed by limestones, which I think is because of a transgression resulting in the deepening of the sea (as mentioned by others in research). Limestones are more characteristic of deeper areas so that's why I think that. I have read articles about this in the past but I'll have to re-read them to fully understand.

Also, if there's anything I got wrong please point it out.

 

 

   

[Tidgy's Dad]

Those are really beautiful. 

[EmileC]

Here's an update: I have spoken to a stromatoporoid specialist and the species has been identified as Actinostroma sp.