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Re: dino-lice

Don Ohmes <d_ohmes@yahoo.com> wrote:

> Is host preference always hard-line?

As obligate ectoparasites, the requirement for a host is hard-line.
For the Rhyncophthirina, the lice that belong to this clade are
parasites on thick-skinned placentals that have little or no hair.
The question arises, did they have the same kind of hosts in the
Cretaceous?  If so, then they needed hosts of that description to
carry them over the K-Pg boundary.  Non-avian dinosaurs can be ruled
out, because they didn't survive the K-Pg.  Large mammals can be ruled
out, because as far as we know there weren't any large mammals in the
Cretaceous (the largest known is _Repenomamus, ~1m long).

> The source of first resort, Wikipedia, mentions Ischnocera and Amblycera in
> addition to Rhync. and Anoplura -- and states that Ischnocera and Amblycer
> are chewing lice that parasitize both birds and mammals. This implies (if
> correct) that closely related chewing lice can inhabit a wide range of taxa.

The Ischnocera, Amblycera and Rhyncophthirina used to be combined into
the group Mallophaga, which comprised all chewing lice.  Now it's
pretty clear that the 'Mallophaga' is paraphyletic, with the
Rhyncophthirina as the sister group to Anoplura (the sucking lice).
All four groups (Ischnocera, Amblycera, Rhyncophthirina, Anoplura)
make up the Phthiraptera, the insect 'order' of parasitic lice.
However, recent molecular phylogenies have found the Phthiraptera to
be polyphyletic, with the Amblycera forming a clade with the
free-living book lice (Liposcelidae, 'order' Psocoptera)... but that's
another story.

To return to your point, any parasitic louse that survive the K-Pg
extinction requires that they had a host that survived the K-Pg
extinction.  This was not such a big deal for the Ischnocera,
Amblycera and Anoplura, because birds and small mammals crossed the
K-Pg.  But for Rhyncophthirina lice to survive the K-Pg extinction
requires that they had a host that was very different to their hosts
today (large, thick-skinned, little or no hair).

 T. Michael Keesey <keesey@gmail.com> wrote:

> There is a gigantic*, putative phthirapteran species known from
> Mesozoic fossils, although its relationships are not well understood.
> Saurodectes vranskyi, from the Early Cretaceous of Siberia (Zaza
> Formation), was about 1.7 cm long and had strangely large eyes for a
> louse. (There's a good photo of the specimen in Grimaldi & Engels'
> excellent book, Evolution of the Insects.)

The original description of _Saurodectes_ proposed that it was a
parasite on pterosaurs.  Grimaldi and Engel agree that it was too
large to have parasitized Cretaceous mammals, which were all small.