aek Posted December 21, 2020 Share Posted December 21, 2020 Any ideas on this partial lichid? Sugar run formation. Measures about a cm. Also on the fence on the other cephalon. Proetid? Thanks for any help. Link to comment Share on other sites More sharing options...
aek Posted December 21, 2020 Author Share Posted December 21, 2020 Link to comment Share on other sites More sharing options...
aek Posted December 21, 2020 Author Share Posted December 21, 2020 @piranha @Kane Link to comment Share on other sites More sharing options...
Kane Posted December 21, 2020 Share Posted December 21, 2020 The two projections on the "lichid" look very similar to that belonging to the Odontopleurid, Ceratocephala goniata. The tubercle scatter makes me slightly less confident about that guess. Although your suspected Proetid is a bit worse for wear in being able to pick out the details of the glabella, the general appearance of the cheek puts me in mind of Cheirurus cf. niagarensis. Scott knows his northeastern Illinois trilobites much better than I do, so it will be his verdict as correct once he weighs in. 3 ...How to Philosophize with a Hammer Link to comment Share on other sites More sharing options...
aek Posted December 21, 2020 Author Share Posted December 21, 2020 Thanks for your input @Kane. The preservation is poor and not much to go on. Ceratocephala is something I considered but something seems off. Link to comment Share on other sites More sharing options...
Kane Posted December 21, 2020 Share Posted December 21, 2020 The only other possibility I can think of at the moment is that it is a lichid, and that what we are seeing is the terminal axial piece of Trochurus welleri. ...How to Philosophize with a Hammer Link to comment Share on other sites More sharing options...
aek Posted December 21, 2020 Author Share Posted December 21, 2020 @Kane that could be a possibility too. I decided to do a little more prepping and more spines were revealed. I think whatever it is is ventral. Link to comment Share on other sites More sharing options...
piranha Posted December 21, 2020 Share Posted December 21, 2020 6 hours ago, Kane said: ...puts me in mind of Cheirurus cf. niagarensis. ..or better yet.. Hadromeros Holloway, D.J. 1980 Middle Silurian Trilobites from Arkansas and Oklahoma, U.S.A. Palaeontographica Abt.A, 170:1-85 4 Link to comment Share on other sites More sharing options...
piranha Posted December 22, 2020 Share Posted December 22, 2020 Because there are very few examples of Trochurus figured in the literature, I consulted with a lichid guru to help determine with more precision, the spiny-barbed specimen. "The specimen belongs to Trochurus welleri Foerste, 1917. Since so little of the specimen is exposed, the orientation is not really clear. However, the two spines on the left are on the median glabellar lobe and the spine on the right is on the posterolateral cranidial lobe. It’s interesting that the specimen is from the Sugar Run; Foerste said that T. welleri came from the Racine but the Sugar Run may not have been recognised as a separate formation at that time; it’s possible that the range of the species extends from the Sugar Run up into the Racine." 4 Link to comment Share on other sites More sharing options...
aek Posted December 22, 2020 Author Share Posted December 22, 2020 @piranha @Kane Thank you both for your help. It is indeed Trochurus welleri. I spent the entire day yesterday carefully prepping out the specimen and was able to extract some of the spines. I thought you might be interested to see how it turned out. 6 Link to comment Share on other sites More sharing options...
Kane Posted December 22, 2020 Share Posted December 22, 2020 Congratulations, and great job on this exquisite example! 1 ...How to Philosophize with a Hammer Link to comment Share on other sites More sharing options...
aek Posted December 22, 2020 Author Share Posted December 22, 2020 1 minute ago, Kane said: Congratulations, and great job on this exquisite example! Thank you! Very happy how it turned out. Link to comment Share on other sites More sharing options...
FossilDAWG Posted December 22, 2020 Share Posted December 22, 2020 Nicely done!! Don 1 Link to comment Share on other sites More sharing options...
piranha Posted December 22, 2020 Share Posted December 22, 2020 "The presence or absence of cranidial spines in lichids is in our view usually worthy of recognition only at the species level, but taken in conjunction with the other differences may warrant the placing of T? welleri and the Arkansas species in a separate genus or subgenus." Thomas, A.T., Holloway, D.J. 1988. Classification and Phylogeny of the Trilobite Order Lichida. Philosophical Transactions of the Royal Society of London, Series B 321:179-262 PDF LINK I'm likin' this lichid! 1 Link to comment Share on other sites More sharing options...
aek Posted December 22, 2020 Author Share Posted December 22, 2020 @FossilDAWG Thank you- it was definitely a difficult prep job! @piranha Thanks for your help and the Holloway paper. Link to comment Share on other sites More sharing options...
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