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Re: dino-lice



On 4/10/2011 8:30 PM, Tim Williams wrote:
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.

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 barrier.

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 least?

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 humanus humanus*...