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Re: feathers and WWD
On Tue, Nov 12, 2013 at 04:29:21PM +0000, evelyn sobielski wrote:
> ...but the case of Mammalia shows that the default position is untenable,
> especially if the
> metabolic rate of theropods was as high as their anatomy indicates. Whether
> anything heavier
> than a horse could maintain a thermal insulation by a dense coat of
> integumentary structures
> (feathers in this case) in the Mesozoic climate (with subtropical conditions
> almost up to the
> polar circles) is very questionable;
Ostriches don't live in amazingly hot conditions?
> phylogenetic reasoning is usually a good approach, but in this case the
> constraint is basic
>physics, and physics always wins over phylogeny: it's hard to maintain your
>lineage if you are
>dead form heatstroke.
So, if I understand you correctly, you're saying that a trex with
feathers is unlikely because the climate was too hot?
So elephants and Hippos are virtually hairless?
> (It is not possible to reconstruct the consequences of *any* major niche,
> metabolic or size shift correctly based on phylogenetic bracketing.
> Elephants, rhinos, pinnipeds, cetaceans - none of these could be
> reconstructed correctly based on data from their relatives.)
> Still, it is quite safe to assume that _Tyrannosaurus_ hatchlings were fully
> And in any case, some physiologist should do the maths. We have enough
> paleoclimatological data and anatomical data that one could take a range of
> reasonable estimates of basic metabolic/heat exchange rates and calculate how
> much of the animal could be covered in how thick an integumentary insulation
> before it fatally overheats.
> But even so, I think it's problematic to imagine an outright plumage
> on nonavian theropods.
> "Fuzz" or ratite-like plumage, no problem with that at least in the small and
> midsized taxa.
> Avian-type plumage is maintenance intense; I am not sure if preen glands
> would leave any fossil
> trace except under the most favorable conditions
> (eg http://link.springer.com/article/10.1007/BF02990211) but these as well as
> a beak
> (ie a sharply pointed snout with keratinous covering) are probably mandatory
> for maintenance
> of an avian-type plumage.
Now THAT is the part that got me. As a parot owner a good part of my
life, and exotic finch owner, birds spend almost all there free time
working on their plumage. They are far worse than teenage girls.
Without a overhwelming survival need, I can't see any species developing
and maintaining full plumage. Mark Norell suggested that we would find
Feathers on saursopods eventually. I guess that would explain the need
for the long neck???
> (What did the avian uropygial gland evolve from? There seems to be very
> little published on this topic.)
> It may also be relevant that there are no dinosaurian feather parasites known
> yet. If ALL theropods (and a lot of other dinos) had full plumage at all
> ages, the nonavians can be expected to have been crawling with parasites,
> since their ability to maintain plumage was lower than in avians and even
> avians are often badly affected (Franklin's comment on the Bald Eagle comes
> to mind). But then again, avian lice fossilize even worse than preen glands:
> Molecular phylogenetics of avian lice might be useful. Though the dating
> would be based on DNA alone and hence be rather spurious, the evidence from
> crown Aves indicates host shifts are common (within multispecies breeding
> colonies as in the Mirandornithes vs Anseriformes, between predators and prey
> such as in accipitrids and pigeons). Given that molecular-clock age estimates
> tend to inflate the presumed age of divergence, and in small r strategists
> strongly so, if molecular clocks place the phthirapteran radiation
> post-mid-Mesozoic, this would strongly indicate that at least *these*
> integumentary parasites only arose when avians did. Any difference between
> Amblycera and Ischnocera early radiation patterns may be interesting, because
> the latter have a much stronger host association than the former.
> A relevant paper (though not incorporating the recent years' insights) is
> http://phthiraptera.info/Publications/41865.pdf - suffice to say that lice
> almost certainly evolved from Psocoptera-like ancestors inhabiting and
> feeding on plant debris used as bedding or nesting material by amniotes.
> There is no direct evidence of use of such materials by nonavian dinos, but
> considering _Mei long_ it is not unreasonable to assume at least the smaller
> taxa used some bedding to line their favorite sleeping sites. In that regard,
> it is again interesting to note that large sparsely-haired mammals prefer to
> rest on soft sediment (eg sand or ash
> http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3466804/) rather than gathering
> bedding material. But whether this is size-related (too time-consuming to
> gather the material) and thus comparable to large dinos, or
> integument-related (no need to keep the integument from soiling) and thus not
> comparable to large dinos in the scope of
> this question, or both, or neither, I don't know. But it's not very
> relevant, because even if large carnivorous theropods used no bedding
> themselves, if smaller dinos did (possible and perhaps likely) and were
> preyed upon by the large guys (certain), host switching would still be
> expected *if and only if* the large guys had in fact sufficient plumage.
> There are three interesting recent papers pertaining to the question, one by
> Grimaldi and Engel (ie entomo guru stuff)
> http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1560062/, a recent review of the
> underlying question
> and a 2011 analysis of the molecular data
> which tentatively points to lice only arising coincident with avians (but see
> also http://www.biomedcentral.com/1471-2148/10/292/ for the problems of the
> molecular approach - for Anoplura it does not work as well as one would like
> it to).
> All things considered I find the hypothesis of full plumage (or similar
> integument) borne by small theropods very convincing, by large and gigantic
> dinosaurs quite weak and possibly even fully untenable.
> Display feathers are a possibility even in the largest taxa, but even the
> presence of quill knobs is not a very strong argument - these only prove
> bird-like remiges somewhere in the ancestry (if remiges are lost, the quill
> knobs might persist until the now-useless phene gets eliminated by a chance
> mutation; quill knobs and remiges are functionally not firmly related and not
> linked genetically; we know this from the non-universal development of quill
> knobs in volant crown Aves* but the evo-devo link is still unclear - they
> might depend on the physical presence of actual feathers to form properly).
> The "phylogenetic bracketing" argument is weak if not fully spurious because
> a) it flatly disregards a soft constraint (maintenance effort - not
> prohibitive, but potentially debilitating), b) it flatly disregards a
> possible hard constraint (thermodynamics - prohibitive if it applies because
> the resultant evolutionary fitness is zero) and c) it can be
> demonstrated to be false if the same question is applied to crown lineages.
> That being said, it's still an open question until someone does the math - we
> know that there is a thermoregulatory threshold, but this needs to be
> calculated even if this calculation will be accurate only to an order of
> magnitude perhaps. In absence of hard figures, it's only notable that extreme
> gigantism and dense integument are apparently only compatible in subarctic
> climates - and as far as anyone can tell, there was no persistent subarctic
> climate *anywhere* during the Mesozoic.**
> * Unfortunately, flightlessness in crown avians tends to quickly reduce the
> ulna to an extent that any persistent quill knobs are obliterated. But
> perhaps _Branta hylobadistes_ has some data to offer in this regard; it's the
> only avian taxon I can think off the top of my head that is known from a
> population containing the whole spectrum from weakly volant to fully
> flightless individuals, and the hypodigm is very good - according to the
> original description (Olson & James 1991) there should be dozens, possibly
> >50 ulnae at USNM and/or BPBM representing all the anatomical diversity found
> in the population. _Branta_ quill knobs are not excessively prominent even in
> long-range migratory species however.
> ** Of course the Mesozoic had the same glacial/interglacial cycle we have
> today, ie there were colder and warmer periods within a generally hot
> climate. It is interesting to speculate if nonavian theropod integument
> *within* any lineage became denser or more extensive during Cretaceous
> glacials. In mammals it apparently did, and mammals are a very good proxy for
> nonavian dinos as regards their ability to shift range in reaction to climate
> change. (At least in the late Mesozoic, after an ecological/ecotrophological
> equilibrium had been established. It's different if a newly evolved and
> competitively successful lineage/radiation is forced to shift range; this
> will likely be successful to the detriment of less sophisticated competitors.)
> Thomas R. Holtz, Jr. <email@example.com> schrieb am Di, 12.11.2013:
> Betreff: Re: feathers and WWD
> An: firstname.lastname@example.org
> CC: email@example.com
> Datum: Dienstag, 12. November, 2013 03:45 Uhr
> Don't forget: Walking with Dinosaurs
> came out in 1999, and was being
> animated in 1998. So at that time the degree of feathering
> coelurosaurs was unknown.
> At present, every single dromaeosaurid for which integument
> is known is
> fully feathered, as are the outgroups Troodontidae,
> Oviraptorosauria, and Therizinosauria. (And we have feathers
> on other,
> more distant outgroups).
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