Devonian Trilobite Trypaulites?

I found the rear section of a Devonian trilobite the other day. It was different than ones I have found before in that the center line or axial lobe was arched up like the roof of a house. These seems to match with a Trypaulites trilobite.

Since the piece is turned over I mold its shape with some Crayola modeling clay.

Silurian and Devonian Corals

Here are some fossils I have found in the Devonian/Silurian period layer or Jeffersonville/Louisville limestone. These fossils were found in Jefferson County, Kentucky.



First is a cross section of a Stromatoporoid sponge.



This next fossil is a cross section of Siphonophrentis elongata horn coral. I normally find this in reddish-brown-white rock but this one is light gray. On the other side it still has texture of the horn coral surface preserved.

Here is a polyp jutting out of the surface of a Heliolites coral.

Here are some pipe organ corals. I have not found a piece this big before. I have been using a ruler I got at the Cincinnati GeoFair 2009 from Kent State University exhibit. It is quite handy.

I am not sure what this next plate is called. It could be Heliolites coraL.

Here is a hemispherical shaped coral that might be some sort of Heliolites.

Another coral I am not sure what it is called. It has some distinctive growth rings.

Here is a Favosites or honey comb coral.

Silurian Horn Coral - A Mystery Solved

Recently, I have been collecting Silurian corals. I found this one which has several interesting aspects. One it shows four horn corals that have budding out of the main one and another coral that has budded out of its base. Second, the smaller horn coral at the base has holdfasts coming out of it.

It is this second point that merits my study today. I have been finding small horn corals with marks on their horn exterior surface and sometimes I find "spines" intact (see green arrows on first picture). At least that is what I assumed till I found this specimen. My thought was they were spines that kept snails from moving up the horn wall (corallum?) to the calice or horn rim. They reminded me of spines on crinoid calyx. I have found what appear to be snail boring holes or track lines on the corallum on other horn corals, so it made sense.

This fossil shows one of them intact that it is holdfast to anchor the smaller horn to the larger horn. So these protrusions were used as anchor lines to bond the corals together in this case.

These pictures where taken quickly under an incandescent light and I was not using a tripod. I will post more about this fossil later since it shows a good example of the budding reproduction process used by horn corals.

Reading up, the book calls the Silurian period, the "Age of Corals". From what I can tell the official coral of that period should be the Halysites chain coral. The Fossils of Ohio book identifies the following phylum has Silurian: Amplexus, Cyathophyllum, Holophragma, Rhegmaphyllum, and Zaphrenthis.