Halysitas?

[dudeman]

Hello,

Here is a nice one I found while fishing here in south central Wisconsin, I am just not sure which one it is. I need help please...

[piranha]

Attached is a link to a few records from the Silurian of Wisconsin and those have only been designated as Halysites sp.

A specific ID might be difficult without an updated faunal list or paper describing the formation you collected the fossils.

LINK

PHOTOS

[piranha]

Here are a few species of Halysites listed from Index Fossils of North America (1944). I have no idea whether they are synonymous or still valid but thought they might be useful for the research to discover how to label your fossil.

H. gracilis

H. catenularia

H. microporus

H. labyrinthicus

Good Luck!

[dudeman]

Thanks Piranha, I need all the help I can get.

[glacialerratic]

Yes, Halysites. Looks like one you can treat with muriatic acid to remove the matrix.

Here's a post I did on the method:

http://www.thefossilforum.com/index.php/topic/16965-halysites-chain-coral/page__hl__halysites__fromsearch__1

[FossilDAWG]

You should also check into Catenipora as a possible genus ID. In Halysites there are tiny corallites interspersed between the larger corallites in the "chain", whereas in Catenipora the tiny coralites are absent. You need to look carefully and have a specimen that is not too heavily silicified to tell them apart. There are numerous Silurian species of both genera, distinguished on the basis of coralite size and length of the "chains" of corallites and size/shape of the "holes" (lacunae) in the colony. There are other genera as well, such as Cystihalysites, that have to be distinguished based on internal structures, but those are usually obscured in silicified specimens. It would help if you could provide a photo directly straight on the colony (not an oblique angle like the ones you posted), and with a metric ruler for scale. An oblique shot of a dime, at a different distance from the camera from most of the specimen, is OK for a general impression of size but it isn't adequate to tell if average corallite size is 0.8 mm vs 1.1 mm for example.

I'm guessing your specimen is Silurian, as that is the source of most such silicified material in Wisconsin/Michigan/Ontario. However there are also Ordovician chain corals, including other Catenipora species, as well as Tollia (=Manipora in the older literature) and rarer forms such as Quepora. "Halysites gracilis" in the old literature has been shown to include both Catenipora and Tollia species, and (as I recall) the type specimens have been lost so no-one knows what they really were, and so the name is rarely used these days. Tollia (Manipora) can be distinguished from the others because it has patches where the corallites are arranged in contact on all sides (like Favosites) as well as areas where the corallites are arranged in chains, all in the same colony. It was probably an intermediate in the evolution of the chain-coral growth from a Favosites-like ancestor with a solid colony form.

Don

Edited November 14, 2011 by FossilDAWG