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Why chitinous?
This article says fish scales are epidermal
The scales article says fish scales are dermal
Is there a real difference between scales/scutes in lepidosaurs and turtles/crocs? —Preceding
unsigned comment added by
Alliumnsk (
talk •
contribs)
14:42, 6 July 2009 (UTC)reply
Yes, lepidosaur scales are epidermal in origin, forming by invagination of the outer skin layer. Scutes are formed in the mesoderm, and later get a horny epidermal covering.
Petter Bøckman (
talk)
21:35, 2 December 2009 (UTC)reply
I cannot find any study to back the claim that reptilian scutes are dermal in origin. Further, the article intimates that scutes are always associated with osteoderms, yet neither the scutes on bird feet, nor the scutes on turtles agree with this association. Scutes seem to be loosely defined as scales that are covered in horn rather than "standard" beta keratin. Unless there is a study to confirm otherwise I suggest removing the "dermal in origin" mentions of reptilian scutes.
Jura (
talk)
15:38, 12 August 2015 (UTC)reply
What's the difference?
What's the difference between scutes and osteoderms? The Wikipedia articles on both mention that each is comprised of bone and skin/keratin/horn. The terms seem redundant to me, unless someone can clarify the difference. - Myrddin_Wyllt 3/13/11 —Preceding
unsigned comment added by
75.64.188.9 (
talk)
18:56, 13 March 2011 (UTC)reply
I think there is some confusion on this page about what scutes are. Scutes are just horn-covered scales. It's a bit of a nebulous term in general, which doesn't help. However, it looks like the definition that has pervaded Wikipedia is one that equivocates scutes with osteoderms. Scutes can have osteoderms, but they are not the same thing.
Jura (
talk)
16:39, 12 August 2015 (UTC)reply
By "horn" do you mean alpha-keratin? Because bird and reptile scales are beta-keratin, yet get called scutes. Frankly, the whole thing seems like a bit of a mess.
HCA (
talk)
17:03, 12 August 2015 (UTC)reply
"Horn", in this case, would not be the same type of "horn" material observed in mammals (which is all alpha-keratin). The horn in reptilian scutes is still composed of beta-keratin, just in higher amounts (more compacted layers) than in other, more maleable scales. Balden and Maderson 1970 (Morphological and Biophysical Identification of Fibrous Proteins in the Amniote Epidermis) give a nice summary of the difference between the limb scales of turtles, and their shell scutes. I think the term "scute" in general has been misused in the literature (especially recently). The way I understand it is that reptiles have scales and scutes. The latter are harder, more compact scales. Birds have scutes and scutellae. The latter may be considered synonymous with scales (maybe). Lastly, some reptiles have scutes and/or scales that may also be underlain by bone (osteoderms), such as the scutes that cover the back osteoderms on crocodylians, or the tuberculate scales that cover the osteoderms in helodermatid lizards.
Jura (
talk)
05:17, 13 August 2015 (UTC)reply
Good to know. However, I think we'll still have an unavoidable level of "I know it when I see it", since we'll be including extinct taxa we can't get histology on. Still, we should definitely lay out an explicit framework in the text of the article.
HCA (
talk)
15:11, 13 August 2015 (UTC)reply
I agree. I'm currently doing a literature search to see if we can get at least one citable source for the definition of scute.
Jura (
talk)
16:41, 13 August 2015 (UTC)reply
I agree it is a confusing topic, probably in part because there has been a lack of accurate definitions that work across the different orders. In turtles scutes are referring to the horny (keratinous) plates on the shell, they have no bone in them, as these are underlaid by a fat layer and then under this are the bones, ie they are separate units. Interestingly the shield on their heads, also made of keratin are referred to as plates or scales, sometimes shields. Crocodilians of course have osteoderms, but not all species, in some those scutes are only made of keratin, this is also of course size related. In the end it may be better to just not use the term as a generalisation and only apply it where it is formally used, in other groups use other terms. Sometimes this will be scale, sometimes scute etc. But this page may be better off being broken up for the different groups of organisisms that have terms that can more or less mean this. This is one of my reasons for taking the section on turtle scutes out of here a few years back and putting it in the page on turtle shells. Cheers
Faendalimastalk17:27, 13 August 2015 (UTC)reply
Turtles
The paragraph on turtle scutes apart from being wildly innacurate is also unreferenced in any way. To solve this my preference is to take it and add it to the
Turtle shell page and then update it and provide a link here to send people on with a summary of the turtle page. Any objections?? Cheers,
Faendalimastalk01:08, 11 November 2011 (UTC)reply