 Order Lichida, or Orders Lichida + Odontopleurida? |
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| Order Lichida, or Orders Lichida + Odontopleurida? |
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Greetings to all!
I'd like to know if it is generally felt that Order Lichida as listed by Fortey 1997 in the Trilobite Treatise (Lichoidea + Odontopleuroidea + Dameselloidea) is being followed, or if that group should be split into two orders: Lichida (Lichoidea only) and Odontopleurida (Odontopleuroidea + Dameselloidea).
Whittington's 2002 paper argued for the strong differences between lichidae and odontopleuridae. Even Thomas & Holloway suggested that if their ontogeny is similar, their evolutionary paths diverged greatly.
It seems only early on, in the Lichakephalidae and Eoacidaspidae that there is some overlap. Some don't like the lumping of Eoacidaspidae into Lichakephalidae, and claim some genera should be put into Odontopleuroidea.
So, what do you think? One Order Lichida with three superfamilies? or Two Orders: Lichida and Odontopleurida?
Thanks!
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Sam [goniagnostus]
A Guide to the Orders of Trilobites
http://www.trilobites.info
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27.08.2007 22:59 |
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Hi Sam,
in first also a smooth welcome from me.
There are servel points to regard:
The Lichidea and Ondontopleuridea are some reason associated.
The only thing is that it seems that the both families are being separated very early.
But this is the same thing with the Order of Phacopida. The families there also have a high diversity.
May a other example is if you take a late and spine beast like a Kroneprusia and you remove all spines, you make its behaviour more flat. It will start to look very lichid.
In the Palaeontology is one trend in the last century (s) the all stuff will being more and more spited. We may can call this overspliting.
The Question is : Did we get more information if we Split the Order Lichida so that we will understand it in a better way.
Well, I would say no.
In the current concept we say Odontopleurids and Lichids they are members of the class Trilobita . Thay are similar and the have the same roots so the are members of the Order Lichida. But they are not the same they are Lichids and Odontoleurids.
In the other concept we would say that they are Trilobites but they are completely different as a Asaphid is different from a Agnostid.
So what you thing?
Greetings
Heiko
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28.08.2007 12:34 |
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goniagnostus 
Registration Date: 27.08.2007
Posts: 68
Thread Starter 
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Actually, the Lichida summary page ordlichida.htm still lists the three superfamily version, but I have indeed created a ordlichida2.htm and ordodontopleurida.htm page, just to see how they would look. I also have drafted a button for Odontopleurida using Selenopeltis as a representative.
At one time, the order Bathynotida was recognized, with a single family and a few genera, based on what seemed a unique rostral plate morphology.
If Lichida is recognized without Odontopleurida, it is only Lichidae and Lichakephalidae
Odontopleurida would be only families Odontopleuridae and Damesellidae
I am still not certain what to do with Eoacidaspididae! The problem is partly that the cephalic features of Eoacidaspididae seem intermediate to Odontopleuridae and Lichidae, and the pygidium seems more akin to Lichidae than Odontopleuridae.
I notice that Richard Fortey posted a blank message on the same topic on the Yahoo forum Trilobites2. I don't know if that was intentional (just to indicate that he is there and reading the thread) or if he will soon say something. Certainly anything he says there would be very instructive!
Sam
| quote: |
Originally posted by Xiphogonium
Having checked your web site, Sam, I found that you already made up your mind assigning independent order status to the Odontopleurida. 
To the best of my limited knowledge an order is defined by being a group of closely related families. I think we are facing the same problems as with lower taxonomy on species level or taxonomy in general.
There seem to be significant differences between the groups in question but I do not have enough morphological knowledge to base my opinion on scientific grounds and my Lichid trilobites are small in numbers.
It would appear that sooner or later what we call "the normative power of the factual" will take its right and break up the Lichida. |
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Sam [goniagnostus]
A Guide to the Orders of Trilobites
http://www.trilobites.info
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28.08.2007 13:10 |
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goniagnostus
Registration Date: 27.08.2007
Posts: 68
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Consider yourself contacted! 
| quote: |
Originally posted by Xiphogonium
Anyone happens to have the Whittington paper available in electronic form? Please contact me! 
LICHIDAE (TRILOBITA): MORPHOLOGY AND CLASSIFICATION
H. B. WHITTINGTON1
Journal of Paleontology; March 2002; v. 76; no. 2; p. 306-320; DOI: 10.1666/0022-3360(2002)076<0306:LTMAC>2.0.CO;2
© 2002 Paleontological Society |
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Sam [goniagnostus]
A Guide to the Orders of Trilobites
http://www.trilobites.info
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28.08.2007 13:14 |
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goniagnostus
Registration Date: 27.08.2007
Posts: 68
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What an interesting post from him! So he is saying that ICZN isn't the deciding body. Your suggestion that what workers choose to use will determine the status of Odontopleurida over time, and I detect from some recent uses of Order Odontopleurida in the literature that the split is occurring!
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Sam [goniagnostus]
A Guide to the Orders of Trilobites
http://www.trilobites.info
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28.08.2007 13:37 |
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goniagnostus
Registration Date: 27.08.2007
Posts: 68
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I think these are good points, and the reason why I have kept Lichida as a single Order so far, though I am testing the water on my website www.trilobites.info with draft pages that split out the Lichida as two Orders. If the Volumes 2 and 3 of the Trilobite Treatise are ever published, it will be interesting to see how this is dealt with...
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Sam [goniagnostus]
A Guide to the Orders of Trilobites
http://www.trilobites.info
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28.08.2007 14:05 |
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Xiphogonium
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I take the liberty of quoting Richard Fortey's comments from the Yahoo Trilobites2 group in here:
-quote-
This question has caused quite a lot of heat in the trilobite community, and I wish there were a definitive answer. I can say that I have recently examined a huge, complete Lichakephalus in Ibrahim Tahiri’s collection in Erfoud, and this leaves me more than ever convinced that it does belong with the rest of the Lichida. If someone would like to buy the specimen for a non-private museum they would be doing the community a great favour (they’d also have to have quite a bit of cash!). I personally believe that Dameselloidea belong with odontopleurids, and set out some of the reasons more than ten years ago. I have since seen ‘odontopleurid protaspides’ in Upper Cambrian silicified samples from Kazakhstan, and they likely come from dameselloids. The argument about whether (or not) to classify Lichida and Odontopleurida together in one clade and taxon depends on how convinced one is that they descended from a common ancestor. If they did they should be classified together. The conservative approach is not to make any such assumptions and continue to separate the groups. In my view there are some larval characters that seem to link the two groups, but I’d be the first to admit that we have a distinct shortage of ontogenies of early members of the larger clade, and these might be the ones that hold the answers. Partly it depends on what you think the origins (of some) of the glabellar lobes of both groups are, and how to trace the homologies. I might say that I also noticed some possible similarities between lichid ontogenies and those of styginids, so I am not putting heavy money on a particular outcome. I’m not convinced it can be settled by voting, though.
-end of quote-
Mike
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28.08.2007 16:33 |
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Rudolf
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Dieser Disskusion kann ich nur bedingt folgen.wäre jemand von den Könner bereit eine Zusammenfassung der Disskusion mal in deutsch zu bringen.
Viele liebe Grüße
Rudolf
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28.08.2007 17:22 |
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Xiphogonium
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EDIT: Just translating for one of our members:
Hallo Rudolf! :-)
Es geht darum ob die Ordnung Lichida, so wie sie von Moore 1959 aufgestellt wurde, so belassen werden sollte oder ob die Unterschiede zwischen den verschiedenen (Super-)Familien nicht vielmehr eine Auftrennung in Lichida und Odontopleurida verlangen.
Heiko und Jens sind offenbar der Auffassung daß man es bei der gegenwärtigen Klassifizierung belassen sollte. Eine gleichlautende Frage wurde von Sam in der Trilobites2-Gruppe gestellt. Er möchte offenbar feststellen wie der Rückhalt für eine solche Aufteilung sein würde, insbesondere weil die "Ordnung" Odontopleurida schon von einigen Workers als solche geführt wird.
Dem Beitrag von Richard Fortey nach zu urteilen ist auch er sich keineswegs sicher, was die richtige Entscheidung wäre, er scheint aber den mehr progressiven Ansatz von Moore zu bevorzugen. Das Problem ist, daß nicht genügend Stadien aus den frühen Entwicklungsstufen dieser Familien zuordnungsbar vorliegen. Erst das würde Hinweise darauf geben ob die Lichida und Odontopleurida auf einen gemeinsamen Vorfahr zurückzuführen sind.
Wäre dem so (was Richard offenbar annimmt), dann wäre die bisherige Zusammenfassung unter der einen Ordnung Lichida korrekt, so wie sie jetzt ist.
Gruß
Mike
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28.08.2007 17:30 |
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Jens
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äh. ja. Wenn wir mal das mit dem Könner weglassen.
Also Problemstellung ist. Im alten Treatise werden Lichida und Odotopleurida als eigenständige Ordnungen aufgefaßt, im neuen Treatise nur als Überfamilien innerhalb der Ordnung Lichida mit einer dritten Gruppe den Dameseloidea, als wahrscheinliche kambrische Schwestergruppe der Odontpleuridae. Es gibt auch die Idee die Lichidae zu den Styginae zu stellen. Die Dameselloidea wurden dagegen bei den Ptyopariden seinerzeit untergebracht, in die man eigentlich fast alles untergebracht hat. Die Asphiden sind ja inzwischen auch ne eigene Gruppe, Und die Styginnae die Schwestergruppe der Scutelliden. Insofern kann man schon verstehen, warum die platten Lichiden auch mit den was zu tun haben könnten. Klarheit werden wohl nur gute Untersuchungen ontogentischer Reihen bringen, aber zur Zeit ist gerade bei den seltenen Formen noch nicht ausreichend vorhanden. Jedenfalls gibt es frapierende Ähnlichkeiten bei den Protaspis-Stadien der Lichidae und Odontopleuridae.
konnte ich weiterhelfen 
Grüsse,
Jens
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28.08.2007 17:54 |
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Rudolf
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Danke Mike,
bin ich der Einzige der da nicht ganz mitgekommen ist oder habe die Anderen nicht den Mut.Ich muß sagen das ich zu diesem Thema noch keine eigene Meinung habe da mir das Wissen und auch die entsprechende Lith, fehlt.Aber man ist ja lernfähig.
Viele liebe Grüße
Rudolf
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28.08.2007 17:54 |
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Rudolf
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Mit Euren beiden Antworten ist mir die Sache schon klarer.
Viele liebe Grüße
Rudolf
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28.08.2007 17:57 |
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