Acarina, pycnogonids, Permian ticks?

[Barry M. OConnor]

At 1:44 PM -0500 4/10/01, Ken Kinman wrote:
>     If Acarina are polyphyletic (i.e., the two lineages are not sister
>groups) as Van der Hammen's research indicates, the parasitiform lineage may
>be a little younger than the acariform.  However, I would still expect to
>see parasitiforms by the Upper Devonian.

I think Van der Hammen's work has been largely rejected because he looked
at a small subset of morphological characters in a small number of exemplar
taxa across the Arachnida.  The monophyletic Acari view, substantiated by
many more characters by Lindquist, is based on the best current evidence.

>      Silurian mites or any Silurian arachnids are something to look forward
>to.  Although scorpions are known from the Silurian, they are not arachnids.
>  Class Scorpionea (incl. eurypterids) goes back at least to the early
>Ordovician, so one can't completely rule out the possibility of Ordovician
>arachnids (but I wouldn't hold my breath).

There is certainly disagreement among arachnologists as to these points.

>      Then there is Class Pycnogonea (sea spiders), which Bonnie Blain
>believes are actually arachnids (supposedly related to mites, but I'm not
>sure which groups of mites she relates them to).  Have any of her papers on
>the pycnogonid-acarina relationship appeared yet?   Unless her evidence is
>particularly strong, I assume such a proposed relationship will be
>controversial.

I haven't seen this proposed as yet.

>     I wrote to Hans Klompen last week about the "hairy" New Jersey tick
>(Carios).  Some of the news reports were misleading, indicating that Klompen
>said ticks originated in South America.  Actually he said the genus Carios
>probably originated in South America, and that the ticks as a group probably
>originated in or near Australia.
>     That may be true, but I disagree with Klompen that ticks probably arose
>in the mid-Mesozoic (Jurassic?).  I think that they will definitely be found
>in the Triassic, probably in the Permian, and an Upper Carboniferous tick
>wouldn't shock me (although again, I wouldn't hold my breath on a
>pre-Permian origin).
>     Therefore I think that there were plenty of ticks in North America
>during the Cretaceous, and Klompen's hypothesis that the New Jersey tick
>hitched a ride on a seabird from South America is rather far-fetched.  The
>genus Carios more likely existed in New Jersey, feasting on New Jersey birds
>of some kind.  So I wouldn't be surprised to find more _Carios_ ticks in the
>Cretaceous of New Jersey.  In my opinion, we should be on the lookout for
>ticks throughout the entire Mesozoic of North America.

This argument harkens back to the days of Harry Hoogstraal who had the
entirety of tick evolution all laid out for us.  Unfortunately, it was
based on his armchair scenarios rather than any hard data.  Klompen's body
of work has the advantage of being strongly based on evidence (both
morphological and molecular), and on the basis of his published
phylogenies, his geographic hypotheses are consistent with the evidence.
This is quite different from the above statements about what could have
been but for which we have no evidence as yet.

-------------------------------------------------------------------------
So many mites, so little time!
-------------------------------------------------------------------------
Barry M. OConnor
Professor & Curator             phone: (734) 763-4354
Museum of Zoology               FAX: (734) 763-4080
University of Michigan          e-mail: bmoc at umich.edu
Ann Arbor, MI 48109-1079  USA