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Re: Most dinosaurs were scaly



Doesn’t Juravenator show evidence of filamentous integument as well (in spite 
of earlier reports to the contrary)? See 
http://phenomena.nationalgeographic.com/2012/12/19/j-is-for-juravenator/

—Ralph W. Miller III
Member of the Society of Vertebrate Paleontology

On Dec 27, 2013, at 9:48 PM, Mickey Mortimer <mickey_mortimer111@msn.com> wrote:

> Is it just me, or does this study seem to suffer from naively assuming body 
> covering doesn't covary with other factors we can test?  In other words, it's 
> obvious if you just plug in known skin coverings over a cladogram, scales 
> will be the ancestral state for Dinosauria.  No one's ever doubted that, Greg 
> Paul included.  The additional factor which has been discussed ever since his 
> 1988 work is of course size.  What happens if you only plot small specimens 
> on the cladogram?  Ornithischians are all fuzzy/spiny, and sauropodomorphs 
> are unknown unless the titanosaur embryos count.  Even if the latter do 
> count, Sciurumimus makes theropods primitively fuzzy despite Juravenator, so 
> that's ambiguous basal Saurischia and fuzzy basal Dinosauria, which only gets 
> more support if pterosaurs are avemetatarsalians.  Maybe Barrett and Evans 
> include a caveat about this assumption, but since taking it into account 
> nullifies their entire conclusion, I don't think it could help.  This isn't 
> even getting into the metabolic and growth evidence that 
> shows increasingly basal archosauromorphs weren't like living 
> 'reptiles'.  You might as well determine ornithischians don't have cheeks 
> based only on their lack in birds, crocs and lepidosaurs.
> 
> Mickey Mortimer
> 
> ----------------------------------------
>> Date: Fri, 27 Dec 2013 10:13:58 -0800
>> From: bcreisler@gmail.com
>> To: dinosaur@usc.edu
>> Subject: Most dinosaurs were scaly
>> 
>> From: Ben Creisler
>> bcreisler@gmail.com
>> 
>> 
>> A news item and the original abstract from the 2013 SVP meeting:
>> 
>> Nature news:
>> 
>> http://www.nature.com/news/feathers-were-the-exception-rather-than-the-rule-for-dinosaurs-1.14379
>> 
>> 
>> The abstract from the SVP Meeting:
>> 
>> 
>> Poster Session III (Friday, November 1, 2013, 4:15 - 6:15 PM)
>> DINOSAUR INTEGUMENT: WHAT DO WE REALLY KNOW?
>> BARRETT, Paul, The Natural History Museum, London, United Kingdom; EVANS,
>> David, Univ of Toronto at Mississauga, Toronto, ON, Canada
>> 
>> Osteoderms and scaly skin impressions are historically well known in 
>> non-avian
>> dinosaurs
>> these structures,
>> many dinosaur taxa possessed other integumentary features, including a
>> range of ‘quills,'
>> filaments, and feathers in non-avian theropods and ornithischians.
>> Feathers and their
>> homologs are commonly regarded as a synapomorphy of either coelurosaurian or
>> tetanuran theropods, but some authors have gone further, using the presence 
>> of
>> ornithischian feather-like structures to suggest that these structures
>> are plesiomorphic for
>> Dinosauria. This inference has wide-ranging implications for dinosaur
>> biology and
>> evolution.
>> However, to date, no studies have attempted to assess rigorously the
>> evolution of
>> dinosaur integumentary structures within a broad phylogenetic context.
>> We compiled a
>> complete database of all epidermal integumentary structures reported
>> in dinosaurs, by
>> major body region, in order to investigate the origin of feather
>> homologs and the
>> evolution of integumentary structures in the clade. Scales are
>> definitively present in
>> virtually all major ornithischian clades. This, and the presence of
>> extensive armour in
>> thyreophorans suggests that genasaurian skins were primitively scaly. 
>> Similarly,
>> sauropodomorphs lack evidence for anything other than scales or
>> osteoderms. Fitch
>> optimization of integument types on dinosaur phylogenies shows that there is 
>> no
>> unequivocal support for inferring a deep origin of feather-like
>> structures, a result
>> supported by maximum likelihood ancestral state reconstructions for
>> these characters.
>> The structures in Tianyulong and Psittacosaurus are best regarded as
>> autapomorphic
>> integumentary modifications, and there is currently no strong evidence
>> that these features
>> are feather homologs. Further work on the chemical composition of
>> these structures, and
>> those in several non-coelurosaurian theropods, is needed. Although
>> ornithodirans exhibit
>> a range of integumentary novelties that may be related to the origin
>> of feathers, theropods
>> are currently the only dinosaurs that display unequivocal e
>> feathers and their
>> direct homologs.