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Re: Most dinosaurs were scaly



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 
>> 39:270–274.
>>> 
>>> 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.
>>