Unknown Fossils With Circular Cross-Section

[Shaunjones72]

Fossils found in sandstone/mudstone(?) in North Wales, near a man-made reservoir called Llyn Brenig, in an upland area called Mynydd Hiraethog, sometimes known as Denbigh Moors. The area's geology "...consists predominantly of Silurian sedimentary shales, mudstones, and siltstones of Wenlock and Ludlow age" (1994 British Geological Survey).

The exposed cross-sections are up to 10mm in diameter. A close look at the side of the rock shows that some of the fossils appear to reach most of the way through the rock, roughly 8-10cm. The internal structure is intricate.

I found a second rock containing similar fossils, but their shape is less obvious.

Any ideas?

Edited July 22, 2014 by Shaunjones72

[Auspex]

I'd wager on colonial coral, but cannot suggest a more specific ID.

[RyanNREMTP]

I too agree on colonial coral from what I can make out in the picture.

[TqB]

It's a good specimen of a Lower Carboniferous rugose coral, Siphonodendron sp.

These are widely distributed as glacial erratics - there are source rocks in North Wales and further afield.

[digit]

Given what appear to be radial septal lines and possibly a columella in the center, I'd be inclined to agree with the general diagnosis of coral but I'd have no clue more specific than that.

Cool rock--would look pretty cool tumbled and polished.

Cheers.

-Ken

Edit: See, there are such great experts on this forum in all kinds of fossil types and TqB provided a great response while I was typing my post.

Edited July 22, 2014 by digit

[Shaunjones72]

Thank you all! Very impressed.

[LanceH]

Have it polished.

[Ludwigia]

I agree with Tarquin. Siphonodendron and a good specimen at that.

[Herb]

nice coral

[Shaunjones72]

Thank you all sincerely. Was kiboshed by the 2MB limit for images, as I have much sharper images too large to post. Will look into getting it polished.

[Shaunjones72]

Here is a close up from the other specimen I found at the same location. It's a flatter, more irregularly shaped rock, and the fossils are less regularly shaped and arranged, but very clear and detailed nonetheless.

[FossilDAWG]

The difference in shape is due to the angle at which the corals are cut by the surface of the rock. The first specimen cuts the corals horizontally, so the individual corallites look circular. In the second specimen the coral is cut at an angle, so the corallites (which are fairly cylindrical) look like irregular ovals.

Don

[Ludwigia]

Thank you all sincerely. Was kiboshed by the 2MB limit for images, as I have much sharper images too large to post. Will look into getting it polished.

You could reduce the size of them using a simple image editing programm like GIMP or Irfan View.

[Shaunjones72]

Thanks Don, that's what I figured.

[Shaunjones72]

You could reduce the size of them using a simple image editing programm like GIMP or Irfan View.

Hi Ludwigia, I could do it easily if I was at home but I am on holiday with only an ipad and patchy wifi connection.

[Ludwigia]

Ok. I was just trying to be helpful, but now I understand your plight.

[Shaunjones72]

Ok. I was just trying to be helpful, but now I understand your plight.

I appreciate your help. Everyone has been extremely helpful and knowledgable.

[Ludwigia]

Thank you for the positive feedback. It does us good to receive such responses.