Lake Ontario Shoreline

[ttantalo]

Found today on the shoreline of Lake Ontario.

 

[Pumpkinhead]

They are Paleozoic corals. What the exact kind is I'm not sure

This has thrown me for a loop. They don't look like tabulates but appear like rugose corals. Rugose corals are also known as tetracorals because the septa (the lines radiating outwards from the center of the circle shapes on the rock) always appear in multiples of four. Sometimes when I'm really bored I'll actually count the septa on my specimens and I consistently get numbers like 80, 60, etc.

Having counted the septa on your specimens here, many of the numbers were 13 and 14. One might have been 16, but it was a little covered up so it was hard to be certain.

So with this in mind, I submit that your fossils are Rugose corals, and many of them were not yet developed enough to have their septa in a multiple of four. I'm looking forward to seeing what other people think

[Pumpkinhead]

Here is a sample picture of a rugose coral, you can see that the cup of the coral looks similar to what you have posted. This is a solitary specimen, but they can also occur colonially

Edited August 23, 2015 by Pumpkinhead

[TqB]

I agree it's a colonial rugose coral. ("Tetracoral" refers to them adding septa in four loci, but not always in an even way so they aren't necessarily in multiples of four.)

Edited August 23, 2015 by TqB

[Pumpkinhead]

Usually I find that the total amount ends up being a multiple of four anyway, so I do tend to use that as a "rule". Thanks for pointing that out.

I do enjoy reflecting upon life while counting septa though. Is that normal?

[Rockwood]

I agree it's a colonial rugose coral. ("Tetracoral" refers to them adding septa in four loci, but not always in an even way so they aren't necessarily in multiples of four.)

There would be septa that were not truly radial to indicate this condition. Would there not ?

Pumpkinhead: For those of us who can't chew gum and walk at the same time this is not normal

Edited August 23, 2015 by Rockwood

[TqB]

There would be septa that were not truly radial to indicate this condition. Would there not ?

Hi Rockwood - not quite sure what you mean - in rugose corals, there are fossulae where septa aren't inserted (but I can hardly ever spot them!)

Edited August 23, 2015 by TqB

[TqB]

Usually I find that the total amount ends up being a multiple of four anyway, so I do tend to use that as a "rule". Thanks for pointing that out.

I do enjoy reflecting upon life while counting septa though. Is that normal?

Counting septa is good meditation practice!

[Rockwood]

Hi Rockwood - not quite sure what you mean - in rugose corals, there are fossulae where septa aren't inserted (but I can hardly ever spot them!)

Newly forming septa are diagrammed as inserting at angles from the perimeter to a point that progresses toward the center along an existing septa in the textbook I have. Is there something about the process that I'm not getting ?

Here is a good online representation of it.

http://www.personal.kent.edu/~alisonjs/paleo/paleolab3cnidaria.htm

Edited August 24, 2015 by Rockwood

[TqB]

Newly forming septa are diagrammed as inserting at angles from the perimeter to a point that progresses toward the center along an existing septa in the textbook I have. Is there something about the process that I'm not getting ?

Here is a good online representation of it.

http://www.personal.kent.edu/~alisonjs/paleo/paleolab3cnidaria.htm

I'm with you now. Yes, insertion happens like that but you may only see it in the juvenile stage, near the base of the corallite. As the corallite grows vertically, the septa often separate, producing a much more regular distribution in cross section further up. For most rugose corals, you need serial sections of the early stages to see how the insertion occurs.

The classic pattern shown in your link and in many textbooks is based, I think, on Zaphrentites which has a simple, archetypal rugose structure where the juvenile insertion pattern often more or less persists up into the adult calice.

Even in that genus it varies - here are five different species, the fifth having lost all trace of this pattern.

In compound corals with long, cylindrical corallites the adult septal section can be stable for much of the length so you see this sort of thing in most sections (Diphyphyllum sp.):

Hope that makes sense!

Edited August 24, 2015 by TqB

[Mike times 2]

Hi, I have an extensive collection of fossils from Lake Ontario. If I post photos, can the group help me identify them? 

 

Thank you!

Michael

[Kane]

8 minutes ago, Mike times 2 said:

Hi, I have an extensive collection of fossils from Lake Ontario. If I post photos, can the group help me identify them? 

 

Thank you!

Michael

Yes, we can. Start your own topic in Fossil ID and post photos. Remember to put something in the photo to indicate scale, such as a ruler or tape measure. 

[FossilDAWG]

Also please number your photos or specimens, and don't put a lot of specimens in one photo.  It is very frustrating to have to count all the photos in order to be able to reply with a suggested ID.  No one wants to start a reply with "in photo 23, the second from the right hand specimen in the fourth row from the top is a...".

 

Don