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Re: Most dinosaurs were scaly



I'd say your objection regarding body size has been made moot by the discovery 
of Yutyrannus (i.e., Yutyrannus was a large animal that showed no sign of 
reduced body covering).

Jason



----- Original Message -----
> From: Mickey Mortimer <mickey_mortimer111@msn.com>
> To: "dinosaur@usc.edu" <dinosaur@usc.edu>
> Cc: 
> Sent: Monday, 30 December 2013 7:23 PM
> Subject: RE: Most dinosaurs were scaly
> 
> Not to be too harsh, but you rather completely ignored my objection regarding 
> body size.  Do the authors take this into account?  Do you think it's 
> worthwhile?  As I said before "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."  If 
> all the authors do is test a hypothesis based on faulty assumptions to find 
> an 
> answer we all know would be found, then I fail to see how it could be the 
> best 
> poster at SVP.
> 
> Mickey Mortimer
> 
> 
> ----------------------------------------
>>  Date: Mon, 30 Dec 2013 15:45:16 -0800
>>  From: pristichampsus@yahoo.com
>>  To: dinosaur@usc.edu
>>  Subject: Re: Most dinosaurs were scaly
>> 
>>  I found this to be the best poster at SVP this year. Ever since the 
> discovery of structures associated with Tianyulong and (to a lesser extent) 
> that 
> one Psittacosaurus individual, there seems to be a growing trend in dinosaur 
> paleontology to assume that all dinosaurs were filamented (all ornithodirans 
> even), in spite of a large collection of scale impressions from all major 
> lineages. Barrett and Evan's analysis represents an actual test of this 
> hypothesis. That neither parsimony analysis nor max likelihood (the latter of 
> which is more amenable to reversals) found filaments to be ancestral to 
> dinosaurs suggests that ancestrally scaly dinos is still the most 
> parsimonious 
> explanation. Admittedly, without data on the tree support values (available 
> for 
> the max likelihood tree at least) or a more detailed look at the methods we 
> can 
> only say so much about the
ould caution against arguments for unique scale-filament intermingling, 
> based on hair distribution in armadillos. Armadillo "scales" are not 
> actually scales but are a unique form of agglutinated hairs (Wu et al. 2004). 
> Pangolins are even weirder as their armour seems to have evolved from the 
> same 
> germinative layers as claws/nails (Spearman 1967). In fact, according to 
> evo-devo studies synapsids probably never had "true" scales (= 
> sauropsid type) as beta-keratin (a
> been found in the integument of mammals (although pangolins do have an 
> analogue).
>> 
>>  As for whether we might be mislead into thinking some pebbly skin texture 
> is actually scaly, it is a cause for concern. Dinosaur skin impressions 
> tended 
> not to receive much description unless they involve filaments. It has only 
> been 
> rather recently that there has been an interest in the scaly coverings of 
> dinosaurs, with Bell (2012) and Davis (2012) offering insights into scale 
> structures and distribution among dinosaurs. Paik et al. (2010) gave the only 
> analysis I'm aware of regarding potential misinterpretation of lithological 
> structures as being integumental,
>>  can occur. A key factor to determining scales vs. lithology (or pebbly 
> skin) seems to be the regularity of the structures. Pebbly skin has raises 
> and 
> cracks that are randomly distributed. Similarly, rainprints and ripple marks 
> may 
> be more uniform but don't interlock and often vary greatly in size from 
> print to print. Scaly skin, on the other hand, tends
>>  to show a more regular patterning of interlocking polygons.
>> 
>>  It's unfortunate that this is only a press release. I talked with Paul 
> at SVP about this being coming out as a paper and he mentioned that it would 
> be 
> published soon. It's too bad this press release may take away a lot of the 
> impact.
>> 
>> 
>>  Jason
>> 
>> 
>>  References
>> 
>>  Bell, P.R. 2012. Standardized Terminology and Potential Taxonomic Utility 
> for Hadrosaurid Skin Impressions: A Case Study for Sauroplophus
95.
>> 
>>  Davis, M. 2012. Census of Dinosaur Skin Reveals Lithology may Not Be the 
> Most Important FActor in Increased Preservation of hardorsaurid Skin. Acta. 
> Paleontological Polonica.
>> 
>>  Paik, S., Kim, H.J., Huh, M. 2010. Impressions of Dinosaur Skin from the 
> Cretaceous Haman Formation in Korea. Journal of Asian Earth Sciences 
> 39:270–274.
>> 
>>  Spearman, R.I.C. 1967. On the Nature of the Horny Scales of the Pangolin. 
> Journal of the Linnean Society (Zoology). 46(310):267–273.
>> 
>>  Wu, P., Hou, L., Plikus, M., Hughes, 
> Suksaweang, S., Widelitz, R.B., Jiang, T-X, Chuong, C-M. 2004. Evo-Devo of 
> Amniote Integuments and Appendages. International Journal of Developmental 
> Biology. 48:249–270.
>> 
>> 
>> 
>> 
>> 
>>> ________________________________
>>>  From: Zach Armstrong <zach.armstrong64@yahoo.com>
>>> To: "dinosaur@usc.edu" <dinosaur@usc.edu>
>>> Sent: Saturday, 28 December 2013 4:53 PM
>>> Subject: Re: Most dinosaurs were scaly
>>> 
>>> 
>>> 
>>> 
>>> I concur with what Mickey has said. I would also like to raise the 
> question of how confidant we can be that the all the scales of dinosaurs are 
> true scales, and are not epidermal structures secondarily derived from 
> feathers 
> due to evo-devo mechanisms?
>>> 
>>> 
>>> At least some evo-devo studies suggest that the reticula scales on the 
> plantar surface of avian feet are actually developmentally stunted feathers. 
> To 
> quote from Dhouailly (2009), "[R]eticula are not true cutaneous appendages, 
> and appear to be feathers
>>> arrested in the initiation step of their morphogenesis: formation of a
>>> slight bump, without a pla
>>  lar suggestions were made by Sawyer and Knapp (2003).
>>> 
>>> At least some non-scale epidermal structures in modern avians 
> morphologically mimic scales too. For instance, the facial wattles of 
> Philepitta 
> schlegeli (Schlegel's Asity) have an appearance to me that mimics scales: 
> http://thefeaturedcreature.com/wp-content/uploads/2012/10/Screen%2Bshot%2B2011-06-05%2Bat%2B7.26.20%2BPM2.png
>> A similar thing can be said about the bare skin on the head and neck of 
> Coragyps atratus (Black Vulture): 
> http://en.wikipedia.org/wiki/File:Coragyps-atratus-002.jpg
>>> 
>>> If all we had were fossilized impressions of these bare skin structures, 
> might we erroneously conclude they were true scales?
>>> 
>>> I also think inferring from osteoderms in thyreophorans and sauropods 
> that their ancestors never had filamentous integumentary appendages (FIAs) 
> might 
> be misleading. Hair sprouts amongst the osteoderms of armadillos for 
> instance: 
> http://upload.wikimedia.org/wikipedia/commons/b/b4/Nine-banded_Armadillo.jpg 
> Do 
> fossil cingulates
> derms? Seems unlikely.
>>> 
>>> 
>>> The same might be true for scaled dinosaurs, even those with osteoderms. 
> Additionally, feathers erupt from scutate scales in some birds on occasion. 
> Sawyer & Knapps (2003) noted, "The growth of feathers from the distal 
> ends of scutate scales occurs occasionally in normally scaled [chicken] 
> breeds 
> such as White Plymouth Rock and White Leghorn.
>>> have been observed growing from the tips of the definitive scale ridges 
> at 12 days of incubation." So scales and feathers intermingling are not de 
> facto impossible, although there appears to be significant developmental 
> constraints. Maybe these constraints were more relaxed during the initial 
> evolution of FIAs in dinosaurs.
>>> 
>>> -Zach
>>> 
>>>> ________________________________
>>> 
>>>>  From: Mickey Mortimer <mickey_mortimer111@msn.com>
>>>> To: "dinosaur@usc.edu" <dinosaur@usc.edu>
>>>> Sent: Friday, December 27, 2013 11:48 PM
>>>> Subject: RE: Most dinosaurs were scaly
>>>> 
>>>> 
>>>> Is it just me, or does this study seem to suffer fr
>>  aively 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 
rk 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
>>>> '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 n
>>  saurs
>>>>>  these structures,
>>>>>  many dinosaur taxa possessed other integumentary features, 
> including a
>>>>>  range of ‘quills,'
>>>>>  filaments, and feathers in non-avian theropods and 
> ornithisc
only 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
>>>>>  homol
>>> nd the
>>>>>  evolution of integumentary structures in the clade
>>>>>  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
>>  re currently the only dinosaurs that display unequivocal e
>>>>>  feathers and their
>>>>> 
logs.
>>>> 
>>>> 
>>>> 
>>> 
>>> 
>>>                            
>