[WORKGROUP] the first pages have been released ! :)

OK, for all the persons who wonder what all this will look like, you can finally find the first three pages ;) More will come soon, but I wished to share with you these ones.

The next ones will certainly be the most important to the study and will certainly "seriously begin the debate" ;)

the first pages

Congratulations Jean-Brice, the new WorkGroup pages have a great look and the introductory paragraphs offer a very clear explanation of the WorkGroup's intent.

Da

Re: [WORKGROUP] the first pages have been released ! :)

JB, allright now this looks like a very serious start :) I hope you're not quickly running out of webspace when the pictures start to come, and don't forget to save some extra space because I am expecting a big group photograph of the workteam in bermuda's ;)

Anyway, I'm looking forward to reading more!

Best regards, Allart.

Hollardops info

Dear Jean-Brice

I have been reading the many comments about Hollardops at the trilobites2 website and how you will attempt to resolve some of the Hollardops problems on your website. Regarding the Hollardops problem, I would like to make my comments, state some of the problems and make some suggestions.

PROBLEMS : Some trilobite workers make two fatal errors when describing trilobites.

1) They assume the species they are describing is the same species that occurs at different stratigraphic levels and at different geographic localities.

2) They illustrate badly prepared specimens and try to compare them.

If one is going to describe a new species, one should collect the material from one stratigraphic bed at one locality and illustrate well-prepared specimens. Morzadec has not done this, which has resulted in 3 different trilobites being referred to Hollardops mesocristata. They are Pl. 7, fig. 6 (Morz 97) from Algeria, Pl. 8, fig. 6 & Pl. 9, fig.1 from Morocco (Morz 01). These three trilobites cannot all belong the species Hollardops mesocristata. Liebermann & Kloc (1997) described P. burtandmimiae and P. hyfinkeli which are Hollardops. Their descriptions are very difficult to follow and the illustrations are not large enough to make comparisons. This has resulted in difficult comparisons with other species of Hollardops. However, because the specimens are well prepared, each species(in my mind) is well understood and comparisons with other species is possible. Because of the above problems, it is easy to understand the confusion regarding Hollardops and all the variations/species.

OBSERVATIONS :

A) Hollardops mesocristata was described from Algeria and the holotype is a small enrolled specimen. Morzadec (97) redescribes this species from specimens collected through a 50-100 meter interval and from localities 40 km apart. From the illustrations I observe two different kinds of Hollardops. One "variety" the cephalon has a maximum number of 6 lenses in a file and a thin anterior border (Pl.6, fig.1 the holotype & Pl.7, fig.1). The other "variety" has a maximum of 9 lenses in a file and wider anterior border (Pl.6, fig.6 & Pl.7 fig.3) While the type material comes from the Erg Djemel area, most of Morzadec's material comes from Marhouma, 40 km away. Even though the holotype is an articulated specimen, I find it difficult to compare it to the larger specimens. One could conclude that what Morzadec illustrates as Hollardops mesocristata is possibly two different species or ontogenetic change. If there is ontogenetic change, where are the illustrated intermediate specimens with 7 & 8 lenses in a file? What needs to be done is collect more material from the type locality of Erg Djemel so the small holotype can be compared to larger specimens to get a better idea what the growth series of Hollardops mesocristata is suppose to look like and determine if it's one species or two.I have also observed that of all the material that Morzadec (01) illustrates from Morocco, none of it can be referred to Hollardops mesocristata. I would conclude that Hollardops mesocristata only occurs in Algeria and has not been illustrated from Morocco.

B) Hollardops hyfinkeli is a valid species and not a junior synonym of Hollardops mesocristata. Hollardops hyfinkeli is probably the most common Hollardops from Morocco. Morzadec (01) illustrates this species in Pl.8, fig.6. No way can Hollardops hyfinkeli be the same as Hollardops mesocristata. In the cephalon, Hollardops hyfinkeli has 10 (11?) lenses in a file, the S3 furrow is convex anteriorly and not straight as illustrated from specimens from Algeria and the glabella is wider. The pygidium is also different that those from Algeria. At the distal end of the lappet, there is a small spine.

C) Hollardops burtandmimiae: In Liebermann & Kloc (1997) the description of H. burtandmimiae is difficult to follow and have poor illustrations of well-prepared specimens. This makes comparisons difficult. Even though Morzadec (01) describes H. burtandmimiae, none of the trilobites he illustrates can be referred to this species. In the cephalon of H. burtandmimiae, there are 7 lenses in a file, the S3 furrow is straight, the glabella is narrower than H. hyfinkeli and the glabella lacks the prominent tubercles. In the pygidium, the distal ends of the lappets come to a point.

D) Hollardops boudibensis: No comments at this time.

E) Hollardops lemaitreae: This species may not be a Hollardops. The cephalon looks like a Hollardops but the pygidium does not. Until an articulated specimen illustrates that the unusual pygidium goes to the cephalon and has 10 thoracic segments, there will be some question as to the generic assignment.

F) Hollardops sp A: Morzadec (01) illustrates specimens (Pl. 9, fig 1-4) of a trilobite that is neither a H. mesocristata nor a H. hyfinkeli. The S3 furrow appears to be straight so it can't be a H. hyfinkeli. The pygidial lappets are very distinct and does not look like either a H. mesocristata or a H. hyfinkeli. It appears to be an undescribed Hollardops.

G) Hollardops sp. B: Morzadec (01) illustrates specimens (Pl. 9, fig 5-8) of a trilobite he refers to H. burtandmimiae. These specimens cannot be assigned to H. burtandmimiae. These specimens differ from H. burtandmimiae by having prominent tubercles on the glabella and a narrower axial lobe on the pygidium. If one compares the pygidium of Morzadec (01, Pl.9, fig. 6a & 7) to Liebermann & Kloc (97, Pl. 21, fig.1&3), I don't know how anyone could conclude they are the same.

CONCLUSIONS : As I was reading through the comments in trilobites2 on Hollardops, there was a lot of confusion as to what species someone had and discussions over some of the variations. As you can see from the above observations, I can distinguish 7 types (species) of Hollardops. Morzadec's (01) article on Hollardops has not been helpful and causes confusion on the species of Hollardops and Liebermann & Kloc (1997) article is difficult to follow. As you work on your Hollardops website, I would restrict H. mesocristata and H. lemaitreae to Algeria; H. hyfinkeli, H. burtandmimiae, and H. boudibensis to Morocco and realize that there could be at least 2 more undescribed species from Morocco. As the species of Hollardops gets sorted out, the numbers of lenses in a file and the number of axial rings in the pygidium may become important. I would also like to aid you in working out some of the Hollardops problems. I have high quality photographs of the holotype of H. hyfinkeli and photographs of other specimens of this species. These photographs will show that this species is not the same as H. mesocristata. I can also produce some high quality photos of H. burtandmimiae so others can better under stand this species. Lastly, I have a Hollardops specimen from Sharaoverland that is supposed to come from Algeria. It looks like some of the material Morzadec (97) illustrates and would be useful to illustrate.

Look forward to hearing from you, Gerald Kloc

Re : Hollardops info

Dear Mr Kloc, Gerald :)

First of all : happy new year. I wish you the best and an excellent health :) I received your mail several days ago and I am very honoured with it :)

I tried to answer you the very day I read it, but made a mistake in my reply and lost all the text... I was so tired that I couldn' rewrite it at that time, mostly due to the analgesia...

Well, it gave me time to think about your observations and I have to admit I have been really impressed. Your knowledge of the region and of the Hollardops genus is amazing to me :) I hope that this study will make it possible to answer the questions you are raise ; I am thinking of particular points like the remark you made concerning the collecting sites of the Erg Djemel. I know of several valuable dealers like Meredith Aaronson, by example, who might help us in collecting specimens from specific points. As a collector, I will ask to her and other sellers if they can get specimens from specific regions that could help us in determining ontogenic variations and changes.

I am currently working on the two next necessary steps of this project and I would be glad to have your opinion on it :)

The first one is to develop rules to take the pictures as the study will be based on pictures, and we need "standards". I don't possess such a a valuable reference as the "Handbook of paleontological techniques" (Kummel and Raup 1965) but several palaeontologists here in France shall help me in this part. I was thinking of things like : "dorsal view of the cephalon : picture taken from 10 cm above the cephalon, plan of the objective lens parallel with the occular plan". What picture do you consider necessary ? I was thinking of a dorsal and a frontal view of the cephalon, a dorsal view of the pygidium to study the number of axial rings, and one specific view of the lappets, and 2 pictures of both eyes. Last but not least, a global picture of the specimen, to appreciate it in a whole and (try to) see if there is no restoration.

I have a cruel dilemna with the whitening technique : shall we impose it to all ?, which will probably mean loosing many specimens as anyone cannot get all the necessay material. I am not even sure this absolutely necessary; I think it will depend on the trilobites... Well, this point is real problem to me.

The second part is the way we will handle the study : either a prospective statistical study, with a "H null" or "H0" hypothesis like the one you propose (i.e. 7 different species or variants, but we shall only consider the Morrocan ones, as I believe we won't collect enough Algerian specimens) and see if the results fits, or simply gather all the morphological datas and see in how many groups they significantly fit... I read Geyer's study on the Moroccan Fallotaspidids that brilliantly explain these problems of variants and propose regression analysis and multidimensionnal scaling (with a reevaluation of Rudolf Kaufmann's biometric methods). I think this is the way we shall handle this study.

Your message is important in the fact that it determines in a certain way the continuation of the events :) It sets precise goals and remarks. If you do agree with it (because I haven't yet officially published the page) I would like to copy/paste it to the pages of the workgroup. You might want to make several corrections to it due to this new "non-private" aspect (in opposite of the message you sent me)

Well, I am sorry, but I need to stop here for the moment (going back to lay a bit). I hope my next message will be to send you the links to the new pages about which I speak above :)

Jean-Brice.

Re : Hollardops info

JB

You have my permission the send my Hollardops email to the workgroup and the trilobites2 group. I did not want to send it to the trilobite group until you had first comments. You are welcome to add your comments.

Regarding pictures :

It would be best if the pictures of the trilobites are whitened and with scale. For best comparisons, this would have to be done. While color pictures look pretty, they are difficult in showing some of the fine details. Like I said before, I can supply some high quality pictures of whitened specimens. However, some people may have pictures of some other species/varities and colored pictures may have to be used. Then at some other time whitened specimens could be used to replace them. You may also have to use some of Morzadec's publised pictures.

The different veiws you suggest sounds good.

If you could get some dealers to get some unprepared Hollardops from Algeria, I would be willing to buy the material. Then I could prepare them and have whitened pictures taken.

Look forward in working with you, Gerry.

Re : Hollardops info

Hello Gerald :)

Thank you very much for your proposition of publishing the message on the YT2G. I know several persons there that will be mostly interested by your comments :)

I post it as soon as this message is sent.

JB.

[WORKGROUP] the first pages have been released ! :)

Hello all.

I received several days ago a message from Gerald Kloc, co-autor of a cladistic based study of the Asteropyginae which lead to an important revision of this subfamily. I post this message only today, as I needed his approval before doing it (I haden't stated at that time on the workgroup site that any messages will be copied there ad integrum).

This is a very constructive message and I think that many would like to react to it, which is easier here than via mail on the workgroup site.

Concerning myslf, the first thing is that I'd would like to sincerely thank Gerald Kloc again for his support in this study. He will be of great help to us.

The second point is jut to remind you that, at that time, you can find the great principles of the study there : groupbasis If you can't find the link, just go to www.trilobite-identification.net . I set up a link to it.

I am waiting for another (great) drawing from Sam, and I will post a page concerning the measurements and the pictures that will have to be done for our study. The drawings from Sam will permit me to clearly show what my text will sometimes try to explain with difficulty ;)

[here is a copy of the above message]

Jean-Brice

Re: [ TRILOBITES ] [Workgroup] A message from Gerald Kloc.

Hey JB,

This is really great news!

This Hollardops study is taking an even more serious path and I for one am both proud and thrilled to have a front row seat on all of this! :) You'd better start quickly with thinking of names for all the new species you are about to describe! ;)

Good luck! Allart

Re: [ TRILOBITES ] [Workgroup] A message from Gerald Kloc.

This is superb, JB. Kloc's comments are detailed and very helpful. Perhaps with Kloc's help, a really good description for the Hollardops spp can be worked out, solving the short-comings of both L&K and M.

Sam

Re: [ TRILOBITES ] [Workgroup] A message from Gerald Kloc.

With all due respect we haven't done very much yet! It is a major step to have an actual researcher take notice and appreciated, but we have yet to actually implement the workgroup.

And I still say once it does get implemented we should have messages about the Workgroup go to one trilobites group (either trilobites or trilobites2) and the general messages sent to the other. Like I said before, this would only make sense once the study group(s) get going.

By the way, I'm glad your're able to get back on the keyboard and I hope your recovery goes well.

Re: [ TRILOBITES ] [Workgroup] A message from Gerald Kloc.

Hello Kjiro2003 :)

Well, when you look at the website, yes, things seem to be a bit static or "sluggish" ;)

This is mostly due to me, as I am looking for serious bases for this study. This is our first attempt in this kind of work, and I think that if the things are strongly based, anything that will be done later will be both easier and much more quicker to set (besides of any corrections that I know that it will be necessary to do, whatever the time I may take to prepare the workgroup).

So, currently, the difficult part concerns the statistical analyses and the software that might be used ;)

JB

Hello Mr Geyer

Hello, my name is Jean-Brice Gayet,

[... introduction to the workgroup, links and so on...]

The aim of it is to see how many species of Hollardops are really present in Morocco, as there seems to be important intraspecific morphogical variations.

I bought (and read) your -simply excellent- work on Moroccan fallostapids. I wanted to know if the methods you used of regression analysis (and eventually MDS) could be adapted to determine generic/specific variations ? It seems that [a phylogenetic analysis] might "split" the genus, when [a morphological one] tend to "lump" it :) In the end, I would rather prefer to lump than split the genus, and show that what have been described is only due to variations.

I received a very detailed mail from Gerald Kloc on the subject, and I am pretty excited to go further.

I am currently working on the methodology part of how to take the pictures of the specimens, but the next step will be to determine what statistical method can be used in our study. I hope you can help me in this, as the statistical methods we usually use in medicine are not exactly the same that you used, and I am not really a statistician :)

I hope this mail finds you well. Thanks in advance :)

JB

Trilobites

Dear Mr. Gayet,

Thanks for your message and apologies for responding in English. My French is so horrible that it is better for both of us if I am writing in English.

I thank you for addressing the problem of Hollardops, which is a classic example for the usual problems which one is faced with as a paleontologists. Indeed, the problem is two-fold: First, there is a limitation of the recognizable characters of a fossil, due to the imperfect preservation. An important consideration is that trilobite identification often requires almost undeformed specimens with information on the external and internal morphology of the carapace. In addition, a purely morphologic approach to the group's systematics will for some trilobite groups not lead to unequivocal results because of a mosaic pattern of character evolution and frequent convergence in morphological details between the relatively similar lower-level taxa of the group.

Controversy also arose during the last years when purely a cladistic approach was considered by some collegues, who tried to designate apomorphic characters. Particularly in relatively smooth trilobites this approach does not function because of a confusion between the concept of a diagnosis and the recognizability of true apomorphies in fossil material. That apomorphies are not identical with and do not involve characters which can be used to define, typify, and recognize fossil arthropods is emphasized by the identification of the proximal endite as the principal apomorphy of stem-group. Trilobite taxonomy in general has to work with recognizable features, which are usually not true apomorphies. The tendency to evolve effaced morphology creates taxonomic problems, but such shared morphologies may also be a clue to systematic relationships and cannot be simply ignored or labelled as worthless plesiomorphy.

Secondly, quantitative measurements to arrive at reliable taxonomic data are an important tool in the interpretation of morphology and taxonomic status of trilobites. However, such quantitative studies include the problem of biased collections. A valid sample has to depict in all probability the morphological structure of the living population, and it rarely does if it is based purely on "collectors items" offered on the fossil market. I would also like to emphasize that statistic analysis automatically tends to produce homogenous data even of (provable) different species if the number of specimens is very high and the specimens are faintly distorted. Insofar, it is important to use both, paleontologic-taxonomic experience and measurements on well preserved specimens to develop a significantly conclusive image/concept of a trilobite species. I hesitate to say that a trilobite species in some cases may remains a matter of debate and forever will. Hopefully, you can live with this.

I am sincerely hoping that I could somehow contribute to your problem although I am only concerned with Cambrian trilobites. Let me know if I can answer palpable questions.

With best wishes for a healthy and successful year 2004,

G. Geyer

==================================================

Prof. Dr. Gerd Geyer

Institut für Paläontologie Bayerische

Julius-Maximilians-Universität Würzburg

Pleicherwall 1

D - 97070 Würzburg

==================================================

Re : Trilobites.

Dr Mr Geyer :)

Thank you very much for your answer.

I must sadly admit that my german is not as good as it used to be, and I think that english will be the language of this conversation :)

I really appreciate the synthesis you made about the difficulties of doing a study on morphological datas to set taxonomical groups. In order to have your opinion on some particular points, I would like to make several comments on the choice of Hollardops as the genus studied for this first test of an internet-based morphological workgroup :

1) Moroccan Hollardops do usually present very few tectonic distortions. At least, this will prevent the use of any software that might correct these distortions for this study, Gott sei dank ;) . In a similar way, Hollardops can be easily very well prepared. Last but not least, in an order to avoid biases of "collection-only" based specimens, we have set precise inclusion criteria that include a good knowledge of the finding localities and the preparators. Moreover, we will try to get specimens from different localities in Morocco. Some of these points are discussed in the inclusion and exclusion criteria I already set online, and some will be precised later (the need of specimens from specific regions, by example).

2) The genus Hollardops is known, a priori, from the Upper Emsian only. That might help us in avoiding some stratigraphic troubles.

3) Hollardops are quite common in Morocco. Your remark concerning the fact that "statistic analysis automatically tends to produce homogenous data even of (probable) different species if the number of specimens is very high and the specimens are faintly distorted" preoccupies me a bit. I hope we will be able to collect symetrical specimen enough, from various sites, to prevent this. As you say, "paleontologic-taxonomic experience and measurements on well preserved specimens" will help too.

By the way, to permit skillful persons to help us in identifying the trilobites, I will post online all the specimens of the study, with high grade resolution pictures. it will hence permit (even if "touching" a trilobite will always be different) to anyone to criticize the data collecting.

4) This study isn't necessarily based on a study of apomorphic characters as we are only trying to set populations inside a genus (at the beginning).

So, my principal question today is, supposing that the data collecting has been acurate even if I know that this is the point that will be the subject of most of the debates (not to speak of the accuracy of the measures ...) : can I use a regression analysis as you did for the Fallostapids to set groups amongst the moroccan Hollardops population that would permit to define species ?

By example, I wondered if the use of several ratios (like genal spine length/cephalon length, occular heigth/occular length and so on) combined to occular arrangement by example, might help us in determining morphological groups that could be assimilied to species. Our concern is that it seems (but this will have to be proven along the study) that some of the morphological characters do present a normal distribution (i.e. not discrete) in the Hollardops genus, and thus, that some species that have been defined could only represent extreme variants.

If a regression analysis seems to be the solution to our problem, what characters would you use ? If you consider this is not the best approach to the problem, could you propose me an alternative solution to handle it ? :)

I wish you a nice day

Jean-Brice

[WORKGROUP] Discussion rooms

The title must be understood with 2 meanings :)

1) I updated the discussion room of the Workgroup Site. Serious questions begin to arise, and I need feedbacks here. The statistical approach of our study is an important point, and if anyone here can help us in this, his help is welcome.

in short, to any statistician here, concerning the Hollardops study : we are trying to set groups of specimens based on morphological characters. The problem is that some of these characters seem to follow a Normal Distribution into the genus. The questions raised by this remark are : what kind of method analysis to use to determine intrageneric groups ? Regression analysis seems the easiest and more logical one (the method Geyer used for a revisions of Moroccan Fallostapids, by example, and that seems to be a powerful tool that has its limits, see mail of Geyer on the site) but phylogenetical analysis might be discussed here (method used by Lieberman & Kloc, by example, to revise the cladistic links of the Asteropigynae).

I don't have yet all the mathematical tools and theory to test them. These methods differ from the ones I use, and I lack the experience to criticize them. That is why I asked in private to Mr. Geyer and Kloc if the method they used seemed to be suitable to our problem.

I think it is time our group acts as a Workgroup : I need everyone's experience here, and I perfectly know that the answer might come from anyone (even including a paleontologist :) ).

Now, the second point :

2) Kjiro2003 proposed to move the [WORKGROUP] discussions to the reborn Yahoo Trilobite Group... Well, now that the group is at our disposal again thanks to Shawn (and moreover not dedicated to LPs ;) ), we might consider moving there. The introdution page could be set with a short introduction of the Workgroups, a notice to newcomers that the "active" group is here (I mean the YT2G) with a link to this group and the drawing of Hollardops made by Sam.

Shawn, would you mind if we use your group as the [WorkgroupS] forum ?

JB

[WORKGROUP] Back !

Well well :)

I am glad to announce you that the methodology pages are "over", at least concerning "my" part. I uploaded the last corrections made by Sam this night to the second and third methodology pages (well, this was tonight here in Europe) at 7.45 am today . What did it consist in ? Here is a short summary :

- The introduction pages explained why we considered this study was necessary and, in a way, precised that we were aware of the limits of such a study.

- The methodology pages will try to propose solutions to these limits. You can read there an excellent text from Gerd Geyer highlighting several problems that particularly concern us (btw, I realize while typing these words that I forgot to mention the precise reference at the bottom of the page...).

The methodology pages are currently limited to 3 pages :

- The first one describes inclusion/exclusion criteria. Something necessary as we simply can't base our study on any Hollardops specimen ;)

- The second page details the morphological characters that we might use in our statiscal analysis. I already mentionned in that page that the lists are quite exhaustive and that many characters might not be needed in the future. Here, though, we need the feedback of all, amateurs and specialists, before going on : did I forget characters ? Is this totally illusory to think that all the measures might be taken/used ? Which of these characters are known to be absolutely useless because of their inherent variabillity (even if this study is based on variability ;) ) ? etc.

- the third page is still "in construction". I mean, I first forgot to make the link active at the bottom of the second page, so to access it, you have to change htpp://...methodology2.htm to .../methodology3.htm in the "adress window" of your web browser. This being done, you will find a discussion on different methods of measuring a trilobite. I remind to all that the use of a micrometric slide caliper would be the best, but are we ready to invest in such a tool ? If not, I already propose 5 solutions that have to be discussed. I am sure that more methods can be found. I hope that a consensus can be found, "scientifically" approved and proven to be valid. Anyway, we all know that this is the second mostly criticizable part of this study (the first one being the collecting/sampling bias of the specimens), and this is why we need to have 2 things to be done : first, validate our measuring methods to reduce at its maximum the inter-individual variability, second take excellent screenshots from multiple angles of the Hollardops that I will upload on the Workgroup site, and that will permit to all to check any specimen of the study (huge advantage of such a work versus classical litterature)

So, the next steps are :

- discuss here (I can't find anymore Shawn's group ?? ) the methodology points resumed above.

- create a "picturial reference example" specimen page as a guide to reference the trilobites specimens in the future.

Last but not least, I remind to all that there is still a discussion to lead on the best statistical method to use in the future. Goal : sort out populations on morphological criteria among a group of specimens, approach similar to what did Lieberman & Kloc in 1997, but at a "specific" level (i.e. not the genus).

I hope my english is good enough to avoid any incomprehension or misinterpretation. Anyway, Sam corrected the pages, and you should refer to them from now on :)

Time to work, to discuss and to propose solutions, folks :) Here is where the words "international workgroup" will take their full significance.

JB

Re: [ TRILOBITES ] [WORKGROUP] Back !

Hi JB,

I looked over the requirements for specimen submissions and for most people who collect commercial trilobites, particularly those from Morocco (the Hollardops included), information about collecting localities is hard to come by. I have pressed dealers for this info and many times even the best of them lack this information. Most of them give a generic location such as Alnif, Erfoud, Atchana or Ofaten when it is given. Many times Atlas Mountains is given! Even superb specimens have this problem. If this generic information is adequate then the sample may be increased, but if we need more precise information such as the layer and formation, this is rarely if ever identified even by those who find and prep them directly.

However, I think we still need to make clear to people here in the club what this Workgroup means particularly to those who have joined us after the discussions last year. To those who are new to this discussion the Workgroup is a collaborative effort to bring together amateur collections in order to do some genus/species diagnoses in line with the professional literature and will be done alongside the normal discussions we've been having. The participation req's are given on the website Jean-Brice refers to.

This does sound exciting and I'm sure glad you are back in the saddle, but I think for this to succeed I know it should start with something acheivable and modest.

Best regards

Re: [ TRILOBITES ] [WORKGROUP] Back !

Hello kjiro,

There are several answers to the inclusion/exclusion criteria :

1) We want this kind of study to be reproducible in the future, this means that we have to set precise and strict criteria from "day one".

2) Specimen collecting might be much easier with anything that is NOT moroccan material. Future studies will be much easier if they concern french or US material by example, as we will have collected it by ourselves. But we wanted here to test our first workgroup on Hollardops because the specimens are often large and complete, not that rare, and last but not least, because of the obvious ambiguities that can be found in the litterature.

We are all aware that the moroccan trilobites need to be studied with a lot of precautions. I would love to have 150 + specimens for this study, but we have to prevent ourselve of the desire to include any suspiscious material just to say "our study is statiscally significant, as we have large populations".

This said, from now on, if you buy a Hollardops and consider to include it in the study, try to have precise infos from your seller. I know that we can ask to people like Meredith, Edcope or Docfossil to get precise geographical infos from their diggers. Maybe older specimens won't be precisely located, but the future ones should be.

I just want to remind that we are not working on the stratigraphical occurence of Hollardops (not feasible unless we dig by ourselves), but its variability.

All this said, we might only have 30 specimens in the end. Maybe more. The question will be : will our results be statistically significant. The answer to this is : our study will take the time to have enough specimens ;)

3) Anyway, and here I hope that Meredith and anyone that digs in Morocco reads this message, a single cephalon (or a pygidium !) whith exact geographical location will be more valuable than a full specimen "found from nowhere" ;) So, Meredith and others, if you have stocks of cephalons and pygidia, please don't throw them away :)

JB