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I'll see what I can do!  I'm quite low on prones as I've been trading or gifting a lot of those in the last while, keeping mostly my finest specimens in the trilobite area of the house. Of course, I still have a few rocks to split and a lot of prep ahead of me!

@Fossil-Hound: This trilobite is no longer considered to be part of the genus Peronopsis. Naimark (2012) reclassified it based on the pygidal characteristics of the type as part of the Morphogroup Vb of the genus Peronopsis, reassigning it as Itagnostus interstrictus.

On 10/27/2017 at 3:32 PM, Douvilleiceras said:

@Fossil-Hound: This trilobite is no longer considered to be part of the genus Peronopsis. Naimark (2012) reclassified it based on the pygidal characteristics of the type as part of the Morphogroup Vb of the genus Peronopsis, reassigning it as Itagnostus interstrictus.

It's a Perenopsis to me and there's some debate as to whether or not these are trilobites.

On ‎10‎/‎29‎/‎2017 at 8:44 PM, Fossil-Hound said:

It's a Perenopsis to me...

Perenopsis => Peronopsis

On ‎10‎/‎29‎/‎2017 at 8:44 PM, Fossil-Hound said:

...there's some debate as to whether or not these are trilobites.

True, but convincing evidence has been supplied to maintain their status in the Class Trilobita. Cotton and Fortey (2005) explained this very well, using cladistics to link the Eodiscina and Agnostina into the Trilobita. Although there are differences between the Order Agnostida and its polymerid counterparts, they concluded that the Agnostida were still derived from trilobites rather than a crustacean ancestor. 

Reference:

Cotton, Trevor & Fortey, Richard. (2005).

Comparative morphology and relationships of the Agnostida.

Crustacea and Arthropod Relationships. 95-136. 10.1201/9781420037548.ch5.

I use Itagnostus interstricta in my labeling, but use Peronopsis as a kind of colloquial term (just as others use Phacops instead of Eldredgeops). Old habits do die hard, but inasmuch as I try to use the most recent nomenclature, at least linguistically I know to what my interlocutor refers. If I were to insist on correct taxonomy in every conversation, I'd quickly find myself with fewer people to talk with!  

On 10/29/2017 at 11:44 PM, Fossil-Hound said:

It's a Perenopsis to me and there's some debate as to whether or not these are trilobites.

On what reasoning do you reject Naimark's analysis?

Don

15 hours ago, FossilDAWG said:

On what reasoning do you reject Naimark's analysis?

Don

Stubbornness @FossilDAWG I suppose some of the old timers still don't recognize Phacops by it's new classification in North America as Eldredgeops. I'm a bit old school on these smaller trilobites. Years ago when I was first introduced to them, I knew them by Perenopsis and I just can't bring myself to calling them any other name. 

OK.  Speaking for myself, as a biologist, these names actually reflect the relationships of these organisms to one another.  The genus name is sort of comparable to our last names (a crude analogy but bear with me).  In the past it was common (especially with difficult groups like agnostids) to have just a few genus names and to shoehorn everything into one of those names.  The effect could be like calling all people with red hair "O'Reilly".  Of course not all people with red hair are from Ireland, nor are they all from the same family.  Names should reflect that, such that only close relatives share the same name.  Of course this is not a great analogy but hopefully you will see the point.  "Peronopsis" had grown to include a few hundred named species.  Naimark looked at each one carefully and found most species had been put in the wrong genus, or they had to be described as new genera because they were too different to be included in any reasonable definition of Peronopsis.

Anyway, if you continue to use Peronopsis for the common Wheeler Shale fossil people will understand what you are talking about.  I just ask that you try to spell it correctly.  It is not Perenopsis.  The Fossil Forum is intended to be a resource for people to use to get information about fossils.  The reason we have tags for our posts is so that people, tomorrow or 10 years from now, can search for information using key words, particularly scientific names.  No-one would search for misspelled names, so those posts would never be found and the information they contain would be lost.

Don