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

[John Grehan]

" 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," - of course this follows if
molecular  and 'other evidence' (what) is correct. I assume, in the absence
of familiarity with the group, that the initial classification was based on
morphology and the new classification is based on molecular similarity and
'other' evidence (morphology). If so, was this a combination approach or
two sets of concordant data. I know of one case where characters for a
morphological phylogeny (for ratites) was subsequently changed to fit in
with a different molecular arrangement.

John Grehan

On Wed, Dec 12, 2018 at 12:31 PM Kenneth Kinman <kinman at hotmail.com> wrote:

> 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‐Hernández, 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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> Nurturing Nuance while Assaulting Ambiguity for 31 Some Years, 1987-2018.
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