Ok Devonian Trilobite - Odontochile Vs Huntoniatonia

[Doug D.]

This trilobite I purchased was labeled as Odontochile syncrama from the Bois d'Arc Formation, Cravat Member, near Clarita, OK. I'm trying to find out more about it- the descriptions and pictures I have seen make it seem more likely that it is some species of Huntoniatonia. It is about 1 and 3/4 inches, or 4 and 1/2 cm, long. I'd be happy to hear some Fossil Forum wisdom about this- thanks!

[piranha]

Odontochile syncrama has 15 pygidial furrows, so Huntoniatonia huntonensis is a much better match.

 

This classic monograph is excellent, but the online version has low quality photo plates.

I'll be happy to send you a better version if you send me a PM with your email address.

 

Campbell, K.S.W. (1977)

Trilobites of the Haragan, Bois D'Arc and Frisco Formations (Early Devonian) Arbuckle Mountains Region, Oklahoma.

Oklahoma Geological Survey Bulletin, 123:1-227

 

OPEN ACCESS PDF

 

 

 

[piranha]

After additional consideration, I'm more confident this one is actually Huntoniatonia lingulifer. Although the characteristic long caudal spine is broken and absent, it has 11 pygidial furrows as noted in Campbell's description. Typically these have a narrower anterior process, but apparently that feature is somewhat variable in this species.

[TNGray]

I had a conversation with Leon Theisen about these bugs. Based on the shape of the glabella "scoop", it should be an Odontochile.

Edited July 10, 2015 by TNGray

[piranha]

On 7/10/2015 at 3:41 PM, TNGray said:

I had a conversation with Leon Theisen about these bugs. Based on the shape of the glabella "scoop", it should be an Odontochile.

 

 

Unfortunately, Campbell 1977 is the only thorough formal description of the Oklahoma dalmanitids.  I have numerous examples in my image library of Huntoniatonia oklahomae that appear to match with the anterior cephalic process and still conform with the expected range of pygidial furrows / ribs, and axial rings of the OP specimen.  I also have similar images that claim to be Zlichovaspis (=Odontochile) syncrama, but do not conform to the expected range of pygidial furrows etc., as described by Campbell 1977.  Adding to the confusion is the limited amount of figured specimens published by Campbell.  Long story short, I would label it Huntoniatonia? sp. (possible undescribed species) until these get a much needed formal revision. 

 

 

Here is one from my image library labeled: Huntoniatonia sp.