Trilobiten.de

[Jens]

Hallo Leute,

habe beim schmökern im Netz mal wieder was Interessantes gefunden. Vor einiger Zeit hat man sich im Yahoo-Forum schon versucht sich den verschiedenen Hollardops-Arten von Marokko zu nähern.

Erfreulicherweise hat sich ein Profi namens Gerald Kloc in die Problematik mit eingemischt und gibt einige Informationen.

Ich bin mal so frech und kopiere die entsprechende englischsprachige Partie aus dem Diskussionsforum von Jean-Brice, siehe auch

http://elas.nerim.net/Workgroup/Discussions.htm


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- 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


Übrigens lohnt es sich auch die weiteren Kommentare in Jean-Brice´s Forum zu verfolgen, da auch Prof. Geyer aus Würzburg um Rat betreffend kambrischer Fallotaspiden gefragt wurde.

Grüsse,

Jens

PS: Mich würde interessieren, wie das Zitat von Liebermann & Kloc (1997) genau lautet. Habs bisher noch net gefunden.

[Jens]

Ein Grund für dieses Thema ist es auch, weil wir (und andere) früher die häufigste Hollardops-Art von Marokko als Metacanthina barrandei Oehlert bezeichnet haben, wie man es auch bei Levi-Setti sehen kann. Ein kurzer Blick in den Treatise zeigte mir aber nun, daß eine solche Bestimmung reichlich Quatsch war, da es sich bei der M. barrandei um die Typusart der Gattung Metacanthina handelt. Sie wurde erstmal aus dem Devon von Frankreich (D´Angers) beschrieben und sieht mit ihren dünnen Stacheln am Pygidium deutlich anders aus als alle Hollardops-Arten.



Nun die häufigste Hollardops-Art ist nach Liebermann & Kloc Hollardops hyfinkeli, da die beiden Autoren die Art seinerzeit noch unter einem anderen Gattungsnamen veröffentlicht haben, lautet der korrekte Name Hollardops hyfinkeli (Liebermann & Kloc, 1997).

Aber es gibt eben noch weitere Hollardops-Arten und wie es scheint sind wie so oft in Marokko auch noch unbeschriebene mit dabei.


Grüsse,

Jens

[Jens]

Ich habe mich ein wenig umgeschaut und ein paar Namen verschiedener Hollardops-Arten gefunden.

Hollardops burtandmimiae (Liebermann & Kloc 1997), aus dem Unterdevon, Marokko
Hollardops hyfinkeli (Liebermann & Kloc, 1997), aus dem Unterdevon, Marokko
Hollardops lemaitreae Morzadec, 1997, aus dem Unterdevon, Algerien
Hollardops mesocristata (LE MAITRE 1952), aus dem Unterdevon, Algerien

Hollardops struvei (MORZADEC 1969), aus dem Ober Ems, Betragne, Frankreich

Hollardops hyfinkeli soll der hauefigste Hollardops in Marokko sein, wahrscheinlich ist es jener, der laufend in unterschiedlichster Qualitaet im Handel zu haben ist. Hollardops burtandmimiae habe ich bisher auf gelblichen Kalken liegend gesehen, ein Fundort war Ofaten.

Vielleicht hilft es ja weiter, falls jemand versuchen sollte mehrere Hollardops-Arten zusammen zubekommen.

Gruesse,

Jens