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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 
> feathered.
> 
> 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: 
> http://vsmith.info/files/papers/fossilReconsidered/download/Fossilsreconsidered.pdf
> 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 
> http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2699.2008.01951.x/abstract 
> and a 2011 analysis of the molecular data 
> http://pubmedcentralcanada.ca/pmcc/articles/PMC3169043/pdf/rsbl20110105.pdf 
> 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.**
> 
> 
> 
> Regards,
> 
> Eike
> 
> 
> * 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. <tholtz@umd.edu> schrieb am Di, 12.11.2013:
> 
>  Betreff: Re: feathers and WWD
>  An: hammeris1@att.net
>  CC: dinosaur@usc.edu
>  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
>  among
>  coelurosaurs was unknown.
>  
>  At present, every single dromaeosaurid for which integument
>  is known is
>  fully feathered, as are the outgroups Troodontidae,
>  Avialae,
>  Oviraptorosauria, and Therizinosauria. (And we have feathers
>  on other,
>  more distant outgroups).

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