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On 4/10/2011 8:30 PM, Tim Williams wrote:
Don Ohmes<email@example.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.
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.
But as to what is possible in terms of host-utilization -- what if
proboscis length mechanically limits host utilization due to
skin-thickness, i.e., a short-snouted chewing louse cannot bite a thick
skinned animal? The inverse would imply that a louse that can penetrate
thick skin can also penetrate thin skin, which would lower at least one
More generally -- does the fact that closely related phthirapterid taxa
parasitize both birds AND mammals imply that some host switching has
been going on at some point? From birds to mammals, or the inverse, at
I am assuming endothermy in birds and mammals evolved separately, and
that lice require a warm-blooded host.
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