Partial Devonian trilobite

[TNDevonian]

This partial cephalon is on a block of lower Devonian Birdsong shale from Parsons. Tennessee USA.

There are several types of Dalmanites in this shale and two other partials are on this same block. The problem is that none of the species that I am familiar with have an anterior margin that wraps around the glabella the way this one does. Even with the margin being broken along a suture, it still doesn't provide a match with anything I am familiar with from this formation, and I can only find a few types that would have this effect if a suture is followed. The lenses are missing from the eyes where they seem to have evenly broken at a suture. Even with it being distressed, the eye position is a bit odd. The closest I can find is Malladaia and it is not a perfect fit. I yield to sharper minds than mine.

 

[Fossildude19]

@piranha

[piranha]

Malladaia is not very similar and is only known from the Eurasian realm. An undescribed species could be a possibility, so I sent the photo to a specialist friend for further evaluation. I will report back with any additional info.

 

 

Flick, U. 2000
Malladaia extrania n. sp. (Trilobita) - Ein Fremdling im Rheinischen Schiefergebirge.
[Malladaia extrania n. sp. (Trilobita) - A Stranger in the Rhenish Slate Mountains.]
Der Aufschluss, 51(4):206-210

[piranha]

As I suspected, this specimen is most likely an undescribed species. One possibility could be the cranidium ‘Dalmanites’ retusus  Dunbar 1920, but it was based on only a pygidium. Because only the pygidium is known, additional cranidia with the associated pygidia of D. retusus  would be necessary in order to reach that conclusion. Pending any future discoveries of this unusual specimen, Dalmanitidae indet. will have to suffice as a temporary label.

 

Dunbar, C.O. 1920

New Species of Devonian Fossils from Western Tennessee.
Transactions of the Connecticut Academy of Arts and Sciences, 23:109-158  PDF LINK

[ScottBlooded]

Suuuuch a cool find!

[TNDevonian]

1 hour ago, piranha said:

As I suspected, this specimen is most likely an undescribed species. One possibility could be the cranidium ‘Dalmanites’ retusus  Dunbar 1920, but it was based on only a pygidium. Because only the pygidium is known, additional cranidia with the associated pygidia of D. retusus  would be necessary in order to reach that conclusion. Pending any future discoveries of this unusual specimen, Dalmanitidae indet. will have to suffice as a temporary label.

 

Dunbar, C.O. 1920

New Species of Devonian Fossils from Western Tennessee.
Transactions of the Connecticut Academy of Arts and Sciences, 23:109-158  PDF LINK

  

D. retusus pygidia are common and Huntonia cranidia are common, but the reverse of both are not, and a full specimen of either would be a very rare find, but would shed some light on the gray areas that cloud the descriptions. Thanks for the effort in finding an answer; I needed verification that it was an undescribed species, or that it may very well be the elusive D. retusus. Perhaps time will tell. Thanks again.