[Taxacom] the lesson of Pentastomids (was: Arthropods and idiots!)

[Kenneth Kinman]

Dear All,
        One variant of the old adage says that people who don't learn from their mistakes are bound to repeat them.  Pentastomids were long classified with other "Lobopodia", until molecular and other evidence showed that they are well-nested within Crustacea.  We should have learned from that mistake, but other "Lobopodia" are still used as outgroups to arthropods.  Although it is less obvious, I believe they are most likely dearthropodized.    It is even less obvious for nematodes, but I suspect they too are dearthropodized and that their ancestors sequentially lost a long list of arthropod characteristics.

         The case of pentastomids should have been a wake-up call:   be very careful what taxa you use as outgroups or your cladistic analysis is likely to give very deceptive results.  When deceptive results are used to create formal taxa, those classifications likewise become deceptive and highly destabilizing.

                          ----------------Ken

________________________________
From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu> on behalf of Kenneth Kinman <kinman at hotmail.com>
Sent: Wednesday, December 12, 2018 9:20 AM
To: taxacom at mailman.nhm.ku.edu; Stephen Thorpe
Subject: Re: [Taxacom] Arthropods and idiots!

Hi Stephen,
       Just as strict cladists of vertebrate paleontology have destabilized vertebrate classification, strict cladists of arthropod paleontology seem to be doing the same to arthropod classification.
       HOWEVER, with arthropods it will likely be much worse if (as I have long believed) their cladistic analyses are very badly misrooted.  At least vertebrate trees are generally well rooted with appropriate outgroups.  If onychophorans, tardigrades, and other ecdysozoans are actually ingroups (and are merely dearthropodized), using them as outgroups has been misleading researchers for many decades.   You can read my postings on that subject (here on Taxacom) back in 2010:
                   http://mailman.nhm.ku.edu/pipermail/taxacom/2010-February/068191.html

                 ------------------Ken

________________________________
From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu> on behalf of Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
Sent: Tuesday, December 11, 2018 9:39 PM
To: taxacom at mailman.nhm.ku.edu
Subject: [Taxacom] Arthropods and idiots!

Firmly in the category of pointless name changes, must be Euarthropoda for Arthropoda, which seems to be catching on, and has been recently adopted by Wikipedia! It all seems to be the result of one paper:

Ortega©\Hern¨¢ndez, J. 2014 (online) 2016 (print): Making sense of ¡®lower¡¯ and ¡®upper¡¯ stem©\group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848. Biological reviews, 91(1): 255-273. https://doi.org/10.1111/brv.12168

Needless to say that there are no formal rules which govern the appropriateness or otherwise of names at this level, and, in the case of Arthropoda, universal usage for hundreds of years should be the main consideration!

Big sigh!

Stephen
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