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Re: Most dinosaurs were scaly

Matt: JINX!!

On Mon, December 30, 2013 8:03 pm, Matt Martyniuk wrote:
> What about testing the possible influence of sedimentology? Something
> similar to what has recently been done for pterosaur and compsognathid
> diversity. How many specimens found as 2d slabs in lagerstatten show
> exclusively scales? How many specimens found as 3d moulds in coarse
> mudstone or sandstone deposits show filaments? It should be possible to
> test for preservation all biases by comparing these variables.
> I agree that the conclusion of this poster has always been obvious and I'd
> go as far as to say it didn't really need testing. If size and taphonomy
> and sedimentology are non factors, the bracket is clear that scales are
> ancestral and ornithischian filaments are probably not homologous with
> feathers or with each other. But nobody has ruled those other factors out
> yet.
> Matt
>> On Dec 30, 2013, at 7:57 PM, Jura <pristichampsus@yahoo.com> wrote:
>> 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
>>> 39:270â??274.
>>>> Spearman, R.I.C. 1967. On the Nature of the Horny Scales of the
>>>> Pangolin.
>>> Journal of the Linnean Society (Zoology). 46(310):267â??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. 48:249â??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)
>>>>>>> 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 â??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.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661

Faculty Director, Science & Global Change Program, College Park Scholars
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA