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Dann Pigdon <firstname.lastname@example.org> wrote:
> Although lice adapated to thick-skinned hosts will probably make their
> presence felt on smaller,
> thinner-skinned hosts (ouch). They may also have trouble clinging to fine
> hairs if they are adapted
> to cling to larger integument.
I suspect that certain adaptations of _Haematomyzus_ (the only extant
member of the Rhyncophthirina) might be secondary, and represent
specializations for parasitizing large mammals such as elephants and
warthogs. These include those features of _Haematomyzus_ that are
directly associated with infesting a sparsely-haired host (such as the
slender one-clawed legs: unable to grip hair or fur) and the long,
drill-like proboscis (for penetrating thick skin).
Thus, it is possible that _Haematomyzus_'s Cretaceous ancestors (stem
Rhyncophthirina) were adapted to infesting small, thin-skinned furry
mammals. These Cretaceous lice had chewing mouthparts that obtained
blood by gouging the skin and feeding on blood pools (telmophagy -
like modern horseflies). This was primitive for the
Rhyncophthirina+Anoplura clade, but the Anoplura modified their
mouthparts for sucking blood directly from vessels (solenophagy). The
Rhyncophthirina survived the K-Pg extinction on small furry mammals,
but were subsequently outcompeted by the radiating anopluran
(blood-sucking) lice and/or other kinds of chewing lice. The only
Rhyncophthirina to persist were those that had at some point switched
to large, sparsely-haired, thick-skinned placentals - where they
remain today. I'd be very interested to know what kinds of lice
woolly mammoths had - they had thick skin, but lots of hair.
So the Rhyncophthirina, despite being around in the Cretaceous, may
never have seen the back - or tasted the blood - of a dinosaur.