Even when many brachiopods are in situ and later encrusted by reefbuilders this does not mean that these brachiopods are actively participing in frame building processes. There might be some Permian brachiopods doing this, but in generally they are passively incorporated in the reef frame.

I suggest some Carboniferous examples where brachiopods can be locally very abundant in the reef frame/fabrics:

Aretz M, Chevalier E. 2007. After the collapse of stromatoporid sponge—coral reefs—the Famennian and Dinantian reefs of Belgium: Much

more than Waulsortian Mounds. Geological Society Special Publications: London; 275: 163–188.

Chevalier, E. & M. Aretz (2005): A microbe bryozoan reef from the middle Viséan of the Namur Syncline (Engihoul Quarry). Geologica Belgica, 8: 109–119.

Mundy, D.J.C., 1994. Microbialite-sponge-bryozoan coral framestones in Lower Carboniferous (Late Visean) buildups of Northern England (UK). Memoir of Canada

Society of Petroleum Geologists, 17: 713-729.

Apart from richtofenids, I've not heard of any reef-building brachiopods. The closest I've seen is in the Late Ordovician of North Wales, where there are occasional pavements of orthids, all embedded vertically in the sediment to create a continuous surface over quite large patches. However, as they didn't cement onto hard substrates, this structure couldn't build up a reef from this point.

What sort of sponges are they? If lithistids, then you can be pretty sure that it was those plus the microbial deposits that formed the framework.

I have never heard of brachiopods as reef builders. They occur in clusters. But they are not reef builders.

I’m mostly agree with the others. Brachiopods, except few exceptions, should not be considered active reef framework builders. It is possible that they were more or less common “passive“ members of reefs during Paleozoic, being generally the most common representative of benthos. A good example is in Watkins (2000).

Taking as reference Harper & Moran (1997) as example, brachiopods with a possible more of less active rule in framework building could be considered those classified as: a) coral like, b) encrusting, c) cemented, d) cosupportive. I think that to consider your brachiopods as active reef builders they should show one of those listened morpho-functional/ecological characteristics. And also in those cases you should evaluate their influence, in terms of biomass, as reef builders.

References:

Harper & Moran, 1997. Fossils Explained 20: Brachiopod life styles. Geology today 235.

Watkins R. 2000 Silurian Reef-Dwelling Brachiopods and Their Ecologic Implications. PALAIOS, Vol. 15, No. 2 , pp. 112-119.

During the Carboniferous, brachiopods are usually simple reef dwellers, although some, especially the cemented strophalosiidines, contribute to the framework. There are examples well known from the Mississippian Waulsortian reefs from the Tournaisian; Craven Reef Belt and the Viséan (Mundy & Brunton, 1985, Brunton & Mundy, 1993). In the Pennsylvanian are less common, although some are known from the Urals and the Canadian Arctic (Carter & Poletaev, 1998), and fron the Cantabrian Mountains (Martínez Chacón & Winkler Prins, 2010). Exceptionally, Sutherland (1996) describes a patch reef composed exclusively by a primitieve Richthofenoid, Ardmosteges orchamus.

Sutherland, P.K. 1996. Ardmosteges orchamus new genus, new species, in the Early Pennsylvanian of Oklahoma - Possible ancestor of the richthofenoid brachiopods. Journal of Paleontology, The Paleontological Society Memoir 46, 25 pp.

I am not a specialist, but a very good reference on the topic is Watkins (2000) PALAIOS, V. 15, p. 112–119 (available at http://www.intl-palaios.geoscienceworld.org/content/15/2/112.full). As I understand from reading some references and from extant species of Brachiopoda (occasionally they can still be found, e.g., in marine sediment samples, despite the fact that most species known were extinct), they are (and were) more reef-dwellers (i.e., their past and present habitats may be reefs) than properly reef-builders.

My experience in study of Muschelkalk brachiopods and observations of brachiopod accumulations in many other formations uphold all previous comments.

No, only in the Permian.

It is correct that brachiopods commonly lived within reefs as dwellers, but not as reef-builders. In Paleozoic reefs of the Urals are many brachiopods association but they didn't be reef builders. They couldn't build reef frameworks.

Antoshkina A.I. Palaeoenvironmental implications of Palaeomicrocodium in Upper Devonian microbial mounds of the Chernyshev Swell, Timan-northern Ural Region. Facies, 2006, 52. p. 611-625.

Antoshkina A., Königshof P. Lower Devonian reef structures in Russia – an example from the Urals // Facies. 2008. Vol. 54. Р. 233-251.

Antoshkina, A. Ecology of Lower Devonian reefs in the Western Urals. – Cour.Forsch.-Inst.Senckenberg. 2003. 242: 111-123. Frankfurt a.M.

Dear all, thank you for the answer. It is very helpful for me to read the answers. I now understand what roles brachiopods would have done within the reefs. I will read carefully references you recommended.

Interestingly, in my case, brachiopods sometimes occupy up to half of reef volume (including what is in the shell). That was the reason that I thought these brachiopods are not simple dwellers, but rather actively involved in reef building. I am still at preliminary stage for this material, and have not understood it yet.

@Joseph Botting: it is hard to identify sponges. I know that they are some kind of demosponge for sure, but I cannot do any detailed taxonomy for them. But, it is likely that they are not typical lithistids. These sponges are preserved as irregular sponge spicule networks, which look similar to the one in following reference (cf. Kwon et al., 2012, http://www.sciencedirect.com/science/article/pii/S0037073812000991).

Are the sponge spicules carbonaceous or siliciacous? Or a mixture? I still maintain that Bryozoa and or Branchiopoda could be the major reef building organisms due to their fragility.

John Paul Jones MSU

@John Jones: Both, but not in mixture. Siliceous are often replaced diagenetically with calcium carbonate in limestones. HTH, Peter.

Reading over my answer I see that a "not" was excluded. Bryozoa were probably not reef builders due to their fragility and/or encrusting nature. Sponges may have calcareous spicules or siliceous spicules and often the two inhabit similar environments. It is possible to find a mixture of different sponge spicules( as this is often the only fossilized evidence of them).

In Silurian some of brachiopods such as Howellella, Microsphaeridiorhynchus, Rhynchotreta, Whitfieldella obviously, reef-dwellers.  They, apparently, settled in small spaces among the rather detached and fine constructions of tabulat-coralls and stromatoporoids (for example Muksha bioherm of Podolia). This promoted and lengthened and rostrum-type umbonal part of shell. It is necessary to note, that brachiopods settled not in all reefs. For example, dense bioherm  of construction in the beginning of ludlovian (Silurian) time consisting from large stromatoporid and corall colonies, were poorly suitable for their settlements. They here meet extremely seldom and as individual copies. More favorable sites for their existence were subbioherm sites, mainly bioherm slopes, which served a place of an attachment, to what the prevalence brachiopods of an anchor type testifies.

I deal with the Paleozoic reefs of the Urals and observed  reefs of different  ages and regions and I didn't see that brachiopods participated in reefs construction as reef-builders. Commonly they lived within reefs as dwellers, but not as .

I do not think brachiopods always build reef and it depends on the sedimentary enviornment. For example,  the brachiopods from deep-water during the Changhsiangian (latest Permian are not related to reef.

Dear all, thank you so much for the answer. I found out that they are acturally bivalves, not brachiopods. Therefore, it is consistent with answers saying that brachiopods are mostly dwellers. I will submit this manuscript soon, and will present it in upcoming GSA meeting.

Dear all, thank you a lot for all your comments. The result of this idea has been published in Palaeo3. Please refer to following link if you are interested:

https://www.researchgate.net/publication/303739185_A_new_Middle_Ordovician_bivalve-siliceous_sponge-microbe_reef-building_consortium_from_North_China

Article A new Middle Ordovician bivalve–siliceous sponge–microbe ree...