Tabulate corals - (Lower Ordovician to Permian) of colonial corals characterized by slender corallites with prominent tabulae and reduced or absent septa (dividing-walls). Tabulate corals were reef builders.

Thanks Joachim, I think that these fossils are coral especially in the photo 1 and 2, but photo 3 I have not idea about it is.

Very welcome! Photo 1 and 2 are clearly like tabulate corals. Photo 1 is a cross-section, photo 2 a top view. Photo 3 is a top view of a rugose coral. Just look up Ordicician tabulate and rugose corals and compare the pictures.

thank you so much, Joachim.

Hi, Ana:

Check for Receptaculites.

Galina Nestell

I am 99 % (if not 100%) sure 1 and 2 are not Tabulate corals. Presumably something Algal, especially on figure 2. Algae of similar kind are quite usual in Ordovician. Number 3 seems to be recrystallized, so I have no exact idea

# 2 resembles a fragment of an alga like Coelosphaeridium. There are a number of algal taxa with such polygonal sections. Also, skeletal fragments of some other organisms like Crinoids may have such polygonal structures on thin sections

Thank you so much, Yury. I'm sad I like the idea that these fossils were corals, because they had been the first in the Middle Ordovician of the San Juan Formation.

I would like to know what the scale represents. Did I miss it some where?

May be Tabulate corals in different sections, not algae!!

These fossils are neither tabulate corals nor rugose corals. Reasons: 1) The skeletal elements are to small. 2) There is no microstructure of corals visible.

It think, these are algae or microproblematica, maybe receptaculitids

Picture 1 and 2 tabulare corals...

For me,  they are tabulate corals.

These are tabulate corals!

I agree with Andreas May - these are not corals. Algae, perhaps, but not receptaculitids.

I agree with Andreas and Yuri. Sure 1 and 2 are not Tabulate corals. Reasons: 1) too small (according to the scale the diameter is quite small for a coral), 2) lack of skeletal elements such as tabulae, 3) too much regularity. I recommend cheking algae.

The first one photo looks like cross-section through small rhombifera pectinirhomb. Second - probably bryozoans or algae.

First picture might be Halysis a problematic cyanophyceae  see paper Munnecke et al. 2001 in N. Jb. Geol. Pal. Mh., 1, 21-42.

the 2nd picture may be Palaeodictyon an enigmatic ichnofossil.

Hello Ana,

my first idea when I have seen the pictures 2 and 3 were similarities with some palaeozoic bryozoans (definitly no corals). But picture 1, and, with a closer view also 2 & 3 are clearly some kind of calcareous algae. You may check the dasyclad sections in FLÜGEL's MIcrofacies of Carbonate Rocks for comparison.

Best regards

Johannes

Thank everyone for your valuable answers.

Can you tell me what the scale represents in the first image?

200 micra

A  wild guess: plant tissue (e.g. tracheids).

First image.

Dear Paul,

non carbonised but micritic calcite tissues of higher continental plants in the middle Ordovician in larger ammounts inside of marine carbonates is a really wild guess... ;)

Best regards

Johannes

Dear Johannes,

You are quite correct. So much for wild guesses!

Best wishes, Paul.

Rhombiferan pectinirhomb for the first, almost certainly. The second could be a section through a holochroal trilobite eye fragment (quite common in Ordovician rocks). The third... maybe a punctate brachiopod fragment? On the other hand, at least some could indeed be algae; you really need more specimens, and to relate the sections to body fossils in the same rock.

For those micrographs, I suppose most of them are green algae.

The first one could be Flabellia, but not very sure.

The second one could be Mastroporella

The third one is perhaps Arthroporella.

I remember already adding an answer? In my opinion this is the problematic alga Halysis. See e.g., Munnecke et al. 2001, N. Jb. Geol. Paläont. Mh., 1 (2001), 21-42.

Thank you so much Yuefeng and Felix.

Yuefeng have any paper about this green algae. 

For the difference between Flabellia and Halysis, you can find the paper from Guilbault et al., 1976, but Flabellia is supposed to be a synonym of Halysis.

For the Macroporella, you can search the paper of Ivan Gusic: The Algal Genera Macroporella, Salpingoporella and Pianella (Dasycladaceae).

And for the last one, I'm not very sure about this, but there is a Chinese reference by Liu et al (2011): Calcareous algae from the Upper Ordovician Lianglitage Formation in the Tarim Basin, Xinjiang, China.

Perhaps the paper from Riding and Fan 2003 also helps. Ordovician Calcified Algae and Cyanobacteria, Northern Tarim Basin Subsurface, China.

Dear Yuefeng: Thank you. 

The best regards.

Ana

You are welcome Ana,

Have a good day.

Best,

Yuefeng