My trilobite of the week.

[piranha]

On 1/29/2019 at 10:58 PM, rew said:

Trilobite #5 is a species of Pragoproetus from Tafroute, Morocco.  It is Early Devonian (Pragian stage) in age. 

 

I checked with a colleague specializing in proetids.  This trilobite is currently undescribed and is not "Pragoproetus" because it is lacking a well-defined preglabellar field and the pronounced anterior border furrow is absent.  Instead it compares more favorably with something similar to Coniproetus eurysthenes nomas Alberti 1969, although it is not that species either.  Most likely this specimen is a new genus of Proetidae.  Congrats on the great acquisition!

 

Coniproetus eurysthenes nomas

 

Alberti, G.K.B. 1969

Trilobiten des jüngeren Siluriums sowie des Unter- und Mitteldevons. Part I. Mit Beiträgen zur Silur-Devon-Stratigraphie einiger Gebiete Marokkos und Oberfrankens.

[Trilobites of the late Silurian, as well as the early and middle Devonian; part 1, Silurian-Devonian stratigraphy of regions in Morocco and upper Franconia.]

Abh. Der Senckenbergischen Naturforschenden Gesellschaft, 520:1-692

 

 

Gerastos granulosus is not a valid species in Morocco.  The species is: Gerastos tuberculatus marocensis

 

 

Gibb, S.L. & Chatterton, B.D.E. 2010
Gerastos (Order Proetida; Class Trilobita) from the Lower to Middle Devonian of the southern Moroccan Anti-Atlas region.
Palaeontographica Canadiana, 30:1-89

[rew]

8 hours ago, piranha said:

I checked with a colleague specializing in proetids.  This trilobite is currently undescribed and is not "Pragoproetus" because it is lacking a well-defined preglabellar field and the pronounced anterior border furrow is absent.  Instead it compares more favorably with something similar to Coniproetus eurysthenes nomas Alberti 1969, although it is not that species either.  Most likely this specimen is a new genus of Proetidae.  Congrats on the great acquisition!

 

Thanks for the info.  That's what I like about this site -- there's always someone who knows more than I do.

[rew]

Trilobite #6 is an Orbitoproetus africanus.  (If this is wrong then I'm 3 for 3 in misidentifying my proetids.)    This trilobite has indentations under the eyes that make it look like it has bags under its eyes.  On the right side view you can see a change in color and texture in the part of the cheek behind the eye.  This looks to me like it was damage done while the trilobite was alive that healed over.  It wasn't easy being small and edible.

[ynot]

That is a bunch of nice trilos You have shown.

Looking forward to what else You have to show.

[DevonianDigger]

On 1/29/2019 at 8:29 PM, rew said:

There are going to be two bugs this week, both humble Proetids.

Trilobite #4.  Gerastos granulosus.  This is a common Middle Devonian trilobite.  This specimen came from Foum Zguid, Morocco.

  

 

First of all, let me say, these are some awesome bugs! I too, am a trilobite collector, and several of these are species I haven't been lucky enough to collect. I'm looking forward to seeing the rest!

 

Second—and I am only doing this because someone did the exact same thing to me, and I'm just paying it forward—this isn't Gerastos granulosus. The proper name, as I was informed, is Gerastos tuberculatus marocensis.

 

Looking forward to the rest of the collection!!! 

[rew]

DevonianDigger, piranha beat you to it -- I've corrected the species name of the Gerastos in my local fossil database.

[DevonianDigger]

5 hours ago, rew said:

DevonianDigger, piranha beat you to it -- I've corrected the species name of the Gerastos in my local fossil database.

 

Lol, he's good like that

[rew]

Today's middle of the week bonus trilobites are both very common bugs.   Neither is the sort of bug with spines or other strange features that collectors lust after, but they dominated their respective ecosystems.

 

Trilobite #7 is Elrathia kingi.  This Middle Cambrian bug from the House Range in Utah is quarried by the tens of thousands.  This specimen is above average size at 37 mm, and was prepared with air abrasion rather than the wire brush treatment these bugs usually get.

[rew]

Trilobite #8 is Flexicalymene retrorsa, which I believe is the most common trilobite of the Cincinnatian Ordovician.  It's an elegant bug, and nicely 3D, and is the one I first show people when explaining what a trilobite is.  This is from the Arnheim Formation at Mt. Orab, Ohio.

[ClearLake]

On 2/6/2019 at 2:04 AM, rew said:

Trilobite #8 is Flexicalymene retrorsa, which I believe is the most common trilobite of the Cincinnatian Ordovician

This is a beautiful specimen indeed and it brings up an interesting question that I'm hoping one of our esteemed members can help me with.  I have dozens of these trilobites that I have collected over the years and ever since my college paleo classes in SW Ohio, they have been Flexicalymene meeki and certainly the most common trilobite of the area.  In the 1996 Fossils of Ohio book, there is F. meeki but no F. retrorsa, same for the Dry Dredgers site and the www.cedarville.edu fossil identification site as well as others.  I know F. retrorosa was described by Foerste at the same time as F. meeki, but as I understand it the differences were very minor (shape of the glabella if I remember correctly) and it seems many authors for decades only used F. meeki.  I now sometimes see the F. retrorsa used as the more common ID and saw a 2007 paper by Hughes and Hunda that seemed to indicate, F. meeki was only found in the Maysvillian strata and F. retrorsa is found in the Richmondian section.  If this is true, or at least the predominant current thinking, when did this change occur?  Can anyone point me to a paper that I can read about this?  Oh, the things that bug me about trilobites (pun intended)!! Thanks in advance for any insight folks can offer.

[piranha]

On 2/7/2019 at 11:42 AM, ClearLake said:

...I know F. retrorosa was described by Foerste at the same time as F. meeki, but as I understand it the differences were very minor (shape of the glabella if I remember correctly) and it seems many authors for decades only used F. meeki.  I now sometimes see the F. retrorsa used as the more common ID and saw a 2007 paper by Hughes and Hunda that seemed to indicate, F. meeki was only found in the Maysvillian strata and F. retrorsa is found in the Richmondian section.  If this is true, or at least the predominant current thinking, when did this change occur?  Can anyone point me to a paper that I can read about this? 

 

 

The size, shape and angle of the anterior border are the distinguishing features that differentiates Flexicalymene meeki and Flexicalymene retrorsa. 

 

Brandt 1980 treated them as synonymous and subsequently Brandt & Davis 2007 regards them as separate based on the description of Ross 1967.

 

 

Flexicalymene cf. F. retrorsa (Foerste) has little to distinguish it from F. meeki except the size, shape, and inclination of the anterior cranidial border. Foerste's original criteria included these and, in addition, lesser cranidial width (trans.) at the posterior border and lack of vestiges of genal spines; I have been unable to substantiate either of these. From Flexicalymene senaria this species does differ in its wider cranidium, straight rather than convex lateral outline of the glabella, inclination and shape of the anterior border, depressed axis of pygidium, and short terminal piece of pygidial axis. The species may have limited stratigraphic use.

 

Ross, R.J. 1967

Calymenid and other Ordovician Trilobites from Kentucky and Ohio.

United States Geological Survey Professional Paper, 583B:1-19  PDF LINK

 

 

Foerste’s species of Flexicalymene, Amphilichas, and Autoloxolichas have survived taxonomic scrutiny (other than reassignment to newer genera), but the many species of Flexicalymene are in dire need of modern taxonomic review. Ross (1967) acknowledged F. retrorsa, but with reservation, as it “has little to distinguish it from F. meeki except the size, shape, and inclination of the anterior cranidial border” (Ross, 1967, p. 15), which are character states that he was unable to substantiate. Ross (1967, p. 16) concluded that “the species may have little stratigraphic use.” Flexicalymene retrorsa minuens has not been referred to in recent literature, and is generally regarded as a synonym of F. retrorsa.

 

Brandt, D.S., Davis, R.A. 2007

Trilobites, Cincinnati, and the "Cincinnati School of Paleontology". pp. 29-50

In: Fabulous Fossil: 300 Years of Worldwide Research on Trilobites.

New York State Museum Bulletin, 507:1-248   PDF LINK

 

 

F. meeki and F. retrorsa were originally distinguished by "more obtuse genal angles" and a more strongly "reflexed" border in F. retrorsa (Foerste, 1910). Foerste elaborated on the distinction in 1919; he explained that F. retrorsa was characterized by "rounded genal angles, a narrower, less triangular cephalon, and a shorter, less nasute anterior border." The results of cluster and discriminant analyses suggested Richmondian trilobites were distinct from Maysvillian forms, but these analyses were not based on the morphologic features Foerste used to distinguish F. meeki and F. retrorsa. I could not substantiate this distinction in genal angles, "reflexion" of the anterior border, and outline of the cephalon with quantitative methods because of lack of enough well-preserved specimens. The anterior border is easily deformed, and measurements of G, G1, and G2 were highly variable, a variation I attribute more to preservation than to allometric growth because many of the specimens show "obvious" compression of the anterior border. The width of the cephalon is also sensitive to deformation by compression of the librigenae along the facial sutures, and these measurements were also discarded as unreliable. Qualitatively, recognition of the differences between trilobites assigned to F. meeki and F. retrorsa is very subjective for the trilobites collected in this study alone show a wide range of variation in the inclination of the anterior border and roundness of the genal angles. Because the criteria used to originally distinguish these species can not be substantiated by quantitative techniques, and because intermediate morphologies are common, I chose to synonomize F. retrorsa and F. retrorsa-minuens with F. meeki.

 

Brandt, D.S. 1980

Phenotypic variation and paleoecology of Flexicalymene (Arthropoda: Trilobita) in the Cincinnatian series (Upper Ordovician) near Cincinnati, Ohio.

MSc Thesis, University of Cincinnati, 148 pp.

 

 

 

figures reprinted and published in:

 

Scheer, A.W. 2019
Flexicalymene Species Determination.

M.A.P.S. Digest 42(2):51-55  LINK

[ClearLake]

WOW!  Now that is what I call a great answer. Not sure how you have all that at your fingertips so quickly, but thank you.  I had read the Ross 1967 paper but not seen either the Brandt 1980 or 2007 papers.  The drawing of the two cephalons is the best depiction of the discriminating differences I have seen.  I assume that is from the Brandt 1980 Masters thesis?  Those are indeed subtle differences.  It seems to me, unless some other literature shows up, there is a lot of uncertainty on the validity of F. retrorosa as a separate species (call me a lumper!!)

 

For my own peace of mind, I'm going to continue to live in my F. meeki world.  Thanks again @piranhafor the info.

[piranha]

Glad to assist!  As mentioned (link added above), the figures are from a privately published paper entitled:

"Flexicalymene species determination." by Al Scheer.  @Roadcut1

 

Here is another excellent thesis that covers this topic:

 

Hanke-Hunda, B.R. 2004

Flexicalymene (Trilobita) from the Cincinnatian Series (Upper Ordovician) of Ohio, Indiana, and Kentucky:

A case study of microevolutionary pattern within a single species lineage in a sequence stratigraphic framework. 

PhD Thesis, University of California Riverside, 248 pp.

[rew]

If there is general agreement that F. retrorsa and F. meeki are the same species, which species gets priority?  Do all the bugs become F. retrorsa or F. meeki?

 

[piranha]

43 minutes ago, rew said:

If there is general agreement that F. retrorsa and F. meeki are the same species, which species gets priority?  Do all the bugs become F. retrorsa or F. meeki?

 

 

Besides the citations posted above, numerous recent authors continue to publish: Flexicalymene retrorsa (Foerste 1910)

The general consensus has not changed, they are still separate species.  Google Scholar has many papers listed: LINK

 

Aucoin, C.D. 2014

Revised Correlations of the Ordovician (Katian, Richmondian) Waynesville Formation of Ohio, Indiana and Kentucky.

MSc Thesis, University of Cincinnati, 106 pp.

 

Brett, C.E., Zambito, J.J., Hunda, B.R., Schindler, E. 2012

Mid-Paleozoic trilobite Lagerstätten: Models of diagenetically enhanced obrution deposits.

Palaios, 27(5):326-345

 

Chestnut, A.J. 2009

Using morphometrics, phylogenetic systematics and parsimony analysis to gain insight into the evolutionary effinities of the Calymenidae Trilobita.

MSc Thesis, Wright State University, 108 pp.

 

Hunda, B.R., Hughes, N.C. 2007

Evaluating paedomorphic heterochrony in trilobites: the case of the diminutive trilobite Flexicalymene retrorsa minuens from the Cincinnatian Series (Upper Ordovician), Cincinnati region. Evolution & Development, 9(5):483-498

 

Koppka, J. 2016

Regenerierte Schalenverletzungen bei Flexicalymene retrorsa aus dem Ordovizium von Ohio, USA.

[Healed shell injuries of Flexicalymene retrorsa from the Ordovician of Ohio, USA.]

3rd German Conference on Trilobites. [Berlin, October, 8th and 9th 2016]. Abstracts of Lectures.

[ClearLake]

1 hour ago, rew said:

If there is general agreement that F. retrorsa and F. meeki are the same species, which species gets priority?  Do all the bugs become F. retrorsa or F. meeki?

Yes, I didn't mean to imply there was "general agreement".  It seems quite clear to me, there is general disagreement and as one or more papers have stated, there is need for a modern taxonomic update of the Cincinnati area Ordovician trilobites.  All I meant was that until that happens, i was going to use F. meeki to represent the common trilobite of the area (as the vast majority of other websites and authors seem to do).  I'll let someone with a much greater vested interest sort out the minutia.  Its always interesting when you dive into the details!!

[rew]

The official trilobite of the week is #9 Harpides sp. from the Fezouata Formation of Zagora, Morocco.   This species has been commercially available for a fair number of years, but has no formal description so far as I know.  So I don't have a species name, and even the genus might change.  This is a natural double, not a composite.  I have a photo of the original split rock showing the partially exposed trilobites on the same rock.

 

[rew]

The first close up:

 

[rew]

The second close up:

 

[ClearLake]

Very interesting !!  Is that coloration natural or some artifact of the preparation process?

[rew]

The color is natural.  It is due to the presence  of iron oxide (rust).

[rew]

Once again I have two midweek bonus trilobites.  These are both Silurian members of the Calymene genus.

 

Trilobite #10  Calymene breviceps from the Waldron Formation of Indiana.

[rew]

Trilobite #11 Calymene niagarensis from the Rochester Shale of Middleport, New York.

[rew]

Now for the official trilobites of the week.  And I use the plural, because there are two closely related trilobites to show.  Both are Ordovician trilobites in the family Trinucleidae.  Like all trilobites in that family, they were eyeless and blind.  The first is #12 Onnia superba, from the Ktaoua Formation in Morocco.  As is often the case, this is named after its closest European equivalent, and may or may not be the same species.

[rew]

Trilobite #13 is Cryptolithus tessellatus from the Trenton Group limestone of Bradford County, Pennsylvania.  Trilobites from the Cryptolithus genus are common enough among Ordovician North American trilobites, but most are poorly preserved in shale.  This one, preserved in limestone, is fully 3D.  I often see the claim that the pits along the rim of the head of these trilobites were for filter feeding, but since I see little evidence that the pits went all the way through the carapace I don't see how that would work.   The earlier idea that the pits contained organs for sensing vibrations makes more sense to me.