Unknown trilobite pygidium

[Collector9658]

This trilobite tail I found today is confusing me, and I can't identify it. Perhaps someone here might?

 

 I didn't notice the trilobite pygidium at first, but glimpsed it after getting a better angle in the daylight. The pygidium is exposed sunkin about 4 inches deep within a block of chert. I oddly found one other example yesterday as well, but it isn't near as nice as the specimen I found today for comparison. The second example is also ventral side of the pygidium exposed.

 

 These Mississippian pygidia are not like others I have collected, even from Burlington Formation chert. I do not believe Exochops is a good match here. Perhaps I am wrong, but I couldn't find anything like it in my resources. These pygidia are covered in ornamentation/ pustules, and the flange almost resembles like what one would see in Ameura or Sevillia. I am uncertain what the best fit would be.

 

 

 

[Collector9658]

For consideration, possibly a Sperngenaspis species? Image is not the best.

 

Photo from- Spergenaspis: A New Carboniferous Trilobite Genus From North America, by David K. Brezinski.

[Fossildude19]

@piranha  @Kane  @GerryK

[Isotelus2883]

It’s a Piltonia.

[Isotelus2883]

I think it is similar to a undescribed species also from Missouri, in a fellow TFF member’s collection.

http://www.crinus.info/trilobites/data/pilt.htm

[Collector9658]

1 hour ago, Isotelus2883 said:

It’s a Piltonia.

There are a few reasons why I can think and assess that it is probably not a Piltonia. Could you share why you think it is?

 

This specimen does not compare the best with Joe's specimen.

Edited 41 minutes ago by Collector9658
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[Isotelus2883]

Similar number of pleural ribs, two sets of axial nodes on either side of the axis, and the defined “lip” around the edge. Although an actual Piltonia does seem to be wider and the “lip”less sharply defined.

[Collector9658]

30 minutes ago, Isotelus2883 said:

Similar number of pleural ribs, two sets of axial nodes on either side of the axis, and the defined “lip” around the edge. Although an actual Piltonia does seem to be wider and the “lip”less sharply defined.

A lot of these Mississippian bugs are notoriously hard to ID. Some being described from just pieces. While it looks alike, I thing it is probably not a Piltonia. I haven't see any reports of Piltonia in the Burlington Formation.

 

I don't think the flange compares well to any Piltonia I can find online.

[Collector9658]

Maybe Australosutura osagensis? Looks closer than Sperngenaspis. I'm out to time to study and look around for now. Photo from- Lower Mississippian Trilobite Biostratigraphy of the Central United States, and Some New Osagean Species, by David K. Brezinski.

 

Edited 20 minutes ago by Collector9658
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