Isotelus?

[Fullux]

Howdy all,

 

Decided to dig back up a few of these Isotelus specimens I found this past summer in the Drakes Formation of Louisville, Kentucky.

 

 

I was showing them to one of my geology professors and she disagreed that they were isotelus, saying instead that they were armored fish remains. One of her reasons was the pores on this piece which I believe to be a hypostome.

 

 

She also said that Isotelus in Kentucky simply don't get larger than 2 to 3 inches (she didn't give an exact length, but she showed me a specimen that was about that large and said that was the max for Kentucky), depsite specimens reaching lengths of more than 10 inches.

 

she showed me a small Isotelus specimen in her collection, and I compared some of its ribs to this piece.

This piece looks like the ribs on hers, just flipped upside down, which checks out, as these are molt fragments of the exoskeleton. You can even see the pleural furrow on this one.

 

I suppose my question would be: Who's right on this?

 

I would include the previous posts I've made on these pieces, but I'm afraid I don't know how.

Edited November 12 by Fullux

[Fossildude19]

Very few fish in the Ordovician, at least, as far as I am aware of.

These look like Isotelus pieces to me. 

 

@Kane  @piranha

[Kane]

I agree.

[Newbie_1971]

Tell her she is crazy, hahaha. They are isotelus 

[EMP]

I’ve definitely found large Isotelus fragments in Kentucky, including a partial cephalon/thorax trilo that was itself 2-3 inches  

All of your specimens are molt fragments from Isotelus, including some nice hypostomes!

[Fullux]

On 11/13/2024 at 10:34 AM, EMP said:

I’ve definitely found large Isotelus fragments in Kentucky, including a partial cephalon/thorax trilo that was itself 2-3 inches  

All of your specimens are molt fragments from Isotelus, including some nice hypostomes!

Thanks for the compliment!

 

An isotelus hypostome has been a bucket list find of mine ever since I started hunting Ordovician deposits. The strange thing is, the specific deposit where I found all these is chalk full of nice Isotelus specimens, many of which are diagnostic. Other sites in other areas of the park only have tiny bits of molt fragments, or nothing at all. What is also strange is those sites with very little isotelus material have tones of corals, especially tabulates. The "isotelus site" as I've been calling it has a rather significant amount of horn corals, but tabulate corals are completely absent!

 

Why do you think that is?

 

Personally, my thought is that maybe that site was where isotelus would gather to molt, as it was free of the obstruction of reefs.

[EMP]

1 hour ago, Fullux said:

Thanks for the compliment!

 

An isotelus hypostome has been a bucket list find of mine ever since I started hunting Ordovician deposits. The strange thing is, the specific deposit where I found all these is chalk full of nice Isotelus specimens, many of which are diagnostic. Other sites in other areas of the park only have tiny bits of molt fragments, or nothing at all. What is also strange is those sites with very little isotelus material have tones of corals, especially tabulates. The "isotelus site" as I've been calling it has a rather significant amount of horn corals, but tabulate corals are completely absent!

 

Why do you think that is?

 

Personally, my thought is that maybe that site was where isotelus would gather to molt, as it was free of the obstruction of reefs.

That’s an interesting observation. I noticed it too, since some sites were chock full of Isotelus parts and others didn’t really have any. My guess is the trilobites gathered in certain areas to molt, maybe for protection or something? Or the deposits were deposited at different times, and the population of Isotelus moved around during that interval. I don’t think there were any environmental factors since I think Isotelus did live in reef environments, except maybe in a reef the molt fragments got disturbed and moved around by other animals, or storms drifted them apart. 

 

Lots of different possibilities.