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paleo

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Sonntag, 14. Dezember 2014, 21:46

Drotops armatus different species?

Hello all,
perhaps anyone has any info on different Drotops armatus species (if exist?)? I am familiar with D. armatus Struve with many long curved spines across the entire thorax, which form two rows on central thoracic lobe. But what about this specimen on photos below, the spines are short and differently distributed (especially on central thoracic lobe) as compared to D. armatus with two rows on central thoracic lobe, this one has three and four rows merging into two rows near the pygidium. There are commercial websites which promote this as a different species ("new", yet undescribed?), but I am interested in your opinion. Any comments welcome! Thank you!!
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Jens

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Sonntag, 14. Dezember 2014, 22:32

Hi Paleo,

yeah, a nice specimen. I try to get my hands on a similar one, but its not easy;-)

Its known to German collectors as Drotops armatus (short spined variant). Struve 1995 described this type only or already as an variant or forma of D. armatus and called it Drotops armatus forma accurata. Such variant-names could be questioned, for me it looks more as a missing link to Drotops megalomanicus then really that close to D. armatus. I say that, because of as you mentioned the different arrangement of the tubercles/spines, particularly on the thoracic lobes. So I would not have a problem to upgrade Struve's forma into a subspecies or to even species level, but the big problem is, we do not know where the Moroccans found that special type.

Is the horizon of such specimens really the armatus-horizon? Struve was not able to give accurat informations in 1995 and there is not much change since that time. We simply do not know if this less spiny specimen is associated with the species we know for sure, or are there much more horizons involved. At least in the Mrakib there are only 2 Drotops horizons, but who knows if they do deliver the same species at different sites?

Some more field work is necessary to answer your question. Maybe we know more in the future.

all the best,
Jens
Was wäre die Welt ohne Trilobiten.
:267: :240: :272:

paleo

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Sonntag, 14. Dezember 2014, 22:47

Hi Jens,
the missing link to Drotops megalomanicus theory really sounds interesting! Great explanation, thank you!

Michael

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Montag, 15. Dezember 2014, 08:47

Hi Paleo,

your Drotops looks really special, unfortunately I can´t help with determination... It looks great for me, and there are a lot of great details on this bug... Really an eyecatcher !
What is the size of this Drotops ? It seems as the Cephalon is prepped from the ventral side, is the hypostoma preserved and visible ?
Thanks a lot for showing this interesting specimen, hope that in future more will be known about these fascinating trilobites from Morocco.
:117:


Best wishes,
Micha

paleo

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Montag, 15. Dezember 2014, 10:30

Hi Micha,
trilobite is a little over 12 cm long and a bit over 6 cm wide. The hypostome is preserved and partially visible. I managed to find some more information regarding this species, looks like four types of spiny Drotops armatus were described by Struve: forma accurata, forma perspinosa, forma armata and forma hoplites.

Thank you!
All the best, Alex.

Michael

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Montag, 15. Dezember 2014, 10:51

Thank you for the information, Alex. Nice big bug, congratulations to this nice trilo !

Best wishes,
Micha

Jens

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Montag, 15. Dezember 2014, 10:53

Hi Alex,

yes this 4 variations have been briefly described by Struve 1995, he suggest that the Drotops armatus is a very variable species, which would be true if all material originates from one single layer. But this is not really sure (for me at least). The Moroccans dug for this spiny Phacopids in the whole Maider region, some trenches are several kilometres long, but the question is, are this everytime and everywhere really contempereous layers. Even for Drotos megalomanicus are 2 different subspecies described, the normal coarse tuberculated one and the less sculptured subspecies subornatus.

Maybe both are from the same layers but did we know it for sure, even the age of the Drotops horizons is in discussion;-) But for me it looks like Struve was right with an Late Eifelian age;-)

all the best,
Jens
Was wäre die Welt ohne Trilobiten.
:267: :240: :272:

Dieser Beitrag wurde bereits 2 mal editiert, zuletzt von »Jens« (15. Dezember 2014, 12:02)


paleo

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Montag, 15. Dezember 2014, 11:45

Hi Jens,
perhaps some of the differences are the case of sexual dimorphism? Lets hope that in the future with more field work more will be known.

Thank you!!
All the best, Alex