U.T.F.! (Unidentified Trilobite Fixigena!)

[Pseudogygites]

It's a UTF! I found this in an exposure of the Ordovician aged Billings Shale Formation. It's clear that it is a Trilobite fixigena, but I was wondering if a Trilobite genus can be identified from one alone? I have found three distinct forms of Trilobite in this formation: Pseudogygites pygidiums, Isotelus fragments, and Triarthrus head pieces. Any ideas? Thank you very much!

[Kane]

I thought the fixigena was the part beside the glabella? What I see here is a glabella, and I would wager it would belong to Pseudogygites latimarginatus (although it is quite similar in appearance to Isotelus gigas).

 

The second picture contains two fragmented pygidia of the same species, with another glabella. To the right of that is a partial impression of a Triarthrus glabella.

[Pseudogygites]

Oops! Sorry for the confusion! What I meant by Fixigena was the glossy, red-ish brown thing in the centre of both pictures. (Glabella). Thank you for the reply! I was also just about to make a post about that mysterious Trarthrus glabella! Two Trilobite Arthropoda hit with one post!

[Kane]

I think you'll find that Pseudogygites and Triarthrus tend to be found together fairly often in that particular layer, in mass moult assemblages. In my experience, the shale by the Ottawa River tend to more or less resemble plates like the one you pictured here with the trilobites being "in colour" (or tending toward a whitish-yellow) whereas the exposures at Strathcona tend to be black like the matrix, but with a kind of slight "rainbow" sheen.