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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.
>>>>
>>>>
>>>>
>>>
>>>
>>>
>