Which Pseuodechenella Is This?

[ClearLake]

I have a mostly complete trilobite that I found this summer at Paulding, Ohio (SIlica Fm, Devonian) which I had assumed was a Pseudodechenella lucasensis, partly because it looks like one and that was the only species of Pseudodechenella that I was familiar with from the Silica (granted, I'm no expert, I've just done some reading).  But in looking at this specimen a bit closer and reading a few of the articles, particularly Stumm's 1965 description of the species, I'm having some doubt on the ID and want to solicit the opinion of the Forum.  I know there are several Devonian trilobite enthusiasts out there and I would appreciate your thoughts.  The primary feature that has me questioning the ID is the lack of a medial groove on the brim of the cephalon which according to Stumm is supposed to be one of the diagnostic features.  I don't see one on this specimen, but could that be a matter of preservation, growth stage, or just variability within the species?  I have seen that P. alpenensis is also found in the Silica Fm. but that appears to have a much wider brim that what this specimen has (about 1mm wide).  There are plenty of other species of Pseudodechenella from other areas of the same age and I have looked at lots of pictures, but not picked an obvious match. Stumm made a comparison to P. rowi, but I am not aware of this species being found in the Silica Fm.   I am working on gathering the descriptions of these various species so I can see if that helps me, but I thought I'd see what some of you thought.  Any ideas are welcome, thanks.

The scale is mm's, it is about 19mm long.

[ClearLake]

And one more picture from a different angle, just for good measure:

 

[Darktooth]

This should be in the fossil ID section. Unless, of course this is up for auction?

[Kane]

Good catch. Topic moved.

[ClearLake]

Ooops, my bad.  Sorry  That what happens when I just start something while looking at a totally different thing.  Thanks for catching that.

[Darktooth]

Nice trilo by the way!

[Kane]

Agreed! I'll bid a dollar!  

[ClearLake]

13 minutes ago, Darktooth said:

Nice trilo by the way!

Thanks

 

11 minutes ago, Kane said:

Agreed! I'll bid a dollar!  

Now look what I've started!!  Nothin but trouble 

[piranha]

According to Lieberman 1994, Pseudodechenella lucasensis should have tubercles on the last 6 thoracic axial rings:

 

Lieberman, B.S. 1994

Evolution of the trilobite subfamily Proetinae Salter, 1864, and the origin, diversification,

evolutionary affinity, and extinction of the Middle Devonian proetid fauna of eastern North America.

American Museum of Natural History Bulletin, 223:1-176  PDF LINK

[ClearLake]

22 hours ago, piranha said:

According to Lieberman 1994, Pseudodechenella lucasensis should have tubercles on the last 6 thoracic axial rings:

I am not seeing those tubercles either, but I recognize that could be a preservation issue. 

 

Thanks for the link, that is a very useful publication.  It may take me a bit to wade through all of it, but I tried to hit all the parts that I think were pertinent to  this specimen.  The two most closely related species to P. lucasensis in his analysis are only known from very incomplete specimens but even so, don't seem to match what I have.  I will work my way through some of the other species to see if I can find something that matches better but I'm open to suggestions.