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Re: dino-lice



Don Ohmes <d_ohmes@yahoo.com> wrote:


> Relative to what is most probable, I am convinced. Any louse ensconced on a
> large dino when the catastrophe occurred was almost surely toast, and any
> resemblance elephant lice have to non-avian dino-lice is most likely due to
> convergence.


Yes, I agree.  There were a whole bunch of weird-ass ectoparasitic
insects known from the Mesozoic, and it's likely that some of these
infested non-avian dinosaurs and pterosaurs.  When these vertebrates
went extinct at the end of the Cretaceous, legions of parasitic
insects would have disappeared with them.  Critters like _Strashila_,
_Saurophthirus_ and _Saurodectes_ may each have been an example of a
diverse and speciose clade of insect parasites.


Until the angiosperms came along, mecopterans (scorpionflies) were
extremely abundant, as major pollinators of Mesozoic gymnosperms (Ren
et al., 2009; Science 326:840-847). When angiosperms radiated and
replaced gymnosperms, the scorpionflies declined, and the butterflies
and beetles really took off.  But, before the scorpionflies crashed,
one branch of scorpionflies had evolved into fleas (Siphonaptera).
Some superficially flea-like insects from the Early Cretaceous might
represent stem-siphonapterans, like _Tarwinia_ and _Niwratia_.  It's
possible that these critters infested pterosaurs or non-avian
dinosaurs.


Other even weirder ectoparasites like _Strashila_ (Late Jurassic) and
_Saurophthirus_ (Early Cretaceous) may belong to other mecopteroid
branches, outside crown Mecoptera.  Lice and things like _Saurodectes_
came from psocopteran stock (booklice and barkflies).


> I am assuming endothermy in birds and mammals evolved separately, and that
> lice require a warm-blooded host.


Apparently the preference that lice have for mammals and birds is not
directly related to body temperature.  According to Grimaldi and Engel
(2005), fleas and lice are limited to hosts with pelage, because
that's how they attach to the host (grasping with their legs).
However, _Haematomyzus_  lice attach themselves using their mouths:
the rostrum is highly modified to anchor the whole louse to the host.
But this can't be the whole story, because the elephant louse (H.
elephantis_) tends to prefer the hairier parts of an elephant.


Ticks and mites also attach themselves to their hosts using their
mouths - and unlike lice and fleas, they also parasitize ectothermic
hosts (reptiles, amphibians).


> Anyhow, it seems possible that the most recent common ancestor of
> Rhyncophthirina and Anoplura inhabited more than just mammals, and may have
> generally looked a lot more like an elephant louse than *Pediculus humanus
> humanus*...


It's possible that the most recent common ancestor in question had a
more anopluran-like body for gripping hair/feathers, but
chewing/telmophagic (bloodpool-feeding) mouthparts like _Haematomyzus_
- but without the elongated proboscis or adaptations to grasp host
tissue with its mouth.




Cheers

Tim