Ordovician Trilobite Microfossil

[Doug D.]

I've had a lot of fun searching through some unsorted microfossil material, and today's find compels me to join The Fossil Forum and post my first message. This fossil is about 2 mm long, and it is from the Lower Pooleville Member of the Bromide Formation of Oklahoma. I show the top and bottom views. Sorry I don't have an ideal camera situation for my microscope! The fossil is very three-dimensional, and it is not easy to focus on the whole piece at once. It resembles the examples labeled Otarion sp. on the id card from D & D Fossils, but I haven't seen much about this species anywhere, and I wonder if anyone here knows a bit about the Bromide trilobites and can share some insights.

By the way, looking at these Bromide microfossils is terrific. It is the trilobites that lured me to them, but there are many other goodies as well. The ostracods have become special favorites. Thanks for your thoughts-

Doug

[piranha]

Otarion had much smaller eyes and the course of the facial suture is a better match with Homotelus bromidensis.

Meraspids and small juveniles had genal spines which were lost when the trilobite became a mature holaspid form.

Attached are two examples of H. bromidensis with genal spines:

 

 

Figure 5 is from:

 

Esker, G.C. (1964)

New Species of Trilobites from the Bromide Formation (Pooleville Member) of Oklahoma.

Oklahoma Geology Notes, 24(9):195-209

Figure 7 is from:

 

Shaw, F.C. (1974)

Simpson Group (Middle Ordovician) Trilobites of Oklahoma.

Journal of Paleontology Memoir 6, Supplement, 48(5):1-54

 

 

 

[Auspex]

Welcome to the Forum

We've a whole section devoted to microfossils, and I hope to see your discoveries there!

[Doug D.]

Thank you, piranha! I have now adopted my adult Homotelus fossil as my relevant avatar. Homotelus was my second guess- no, really!- but I was thrown off by that ID card and by the beautiful hexagonal ommatidia on the microfossil. Now that I have seen the Shaw paper, I will definitely look over the other "Otarion" pieces I have collected. I gather Otarion is rare in this formation, and the common species is the logical choice...I'm not used to seeing facets in Homotelus eyes. I never looked closely, and now I wonder how small and how many there are.

Auspex, thanks for the welcome. I would love to share more of my finds, maybe over the Christmas break when I should have more time to indulge this hobby!