Talk:Placoderm

message: In the "See Also" section, do people think it's best to leave Dunkleosteus terrelli as it is, pointing at a redirect, or change it to Dunkleosteus terrelli, which doesn't redirect but doesn't look as nice. 193.63.43.10 13:32, 26 March 2007 (UTC)
thread_title: Untitled

message: I'll have to delete this link, the article doesn't work
http://www.amonline.net.au/archive.cfm?id=1137
--HoopoeBaijiKite 20:50, 18 June 2007 (UTC)
thread_title:  Article doesn't exist 

message: Why is it so horrible to use this picture  in the taxobox?--Mr Fink (talk) 05:18, 21 April 2008 (UTC)
replies: text: Nothing wrong in terms of accuracy as fas as I can tell, so why not using it either in the taxobox or in the text? ArthurWeasley (talk) 20:15, 21 April 2008 (UTC)
thread_title:  Taxobox Picture Question 

message: " ...when more fossil specimens were found, especially the exceptionally well-preserved fossils from the Gogo Reef formation in Australia, Stensiö's theory of sharks and placoderms as sister groups became accepted as fact."
This statement is misleading. While Stensiö's work remains highly respected, the idea of a sister-relationship between chondrichthyians and placoderms has been almost universally rejected by vertebrate palaeontologists since the mid-1990s. The current consensus is that placoderms are stem-gnathostomes and are thus no more closely related to sharks than bony fish are. The Gogo fossils provided strong evidence *against* a placoderm-shark relationship (Gogo placoderms show separate bone for the nasal capsules which are incorporated into the braincase of sharks and bony fish). If no one objects, I will rewrite this section ASAP.
REFS = 
Goujet, Daniel & Young, Gavin (2004). Placoderm anatomy and phylogeny: new insights. (in) Arratia, Wilson and Cloutier (eds) Recent Advances in the Origin and Early Radiation of Vertebrates. Verlag Dr. Friedrich Pfeil, Munchen, Germany.
Young, G.C. & Goujet, D. & Lelievre, H. (2001) Extraocular muscles and cranial segmentation in primitive gnathostomes - fossil evidence. J. Morphology. 248:304.
Phillipe Janvier's page at the tree of life = http://www.tolweb.org/Gnathostomata/14843
John Long - personal communication.
Ozraptor4 (talk) 01:46, 13 June 2008 (UTC)
replies: text: We should elaborate more on why Stensiö's theory has been rejected in favor of placoderms being stem-gnathostomes, like, listing some more traits that the Gogo reef placoderms have demonstrated to have in common with all/most other gnathostomes.--Mr Fink (talk) 03:30, 13 June 2008 (UTC)

text: Absolutely - the process which settled the relationships of placoderms to other fish was as intense and complex as the bird-dinosaur ancestry debate. I have most of the key papers on the subject but will take a little while to condense the main points into a succinct and readable account. Note that the Gogo placoderms were probably eclipsed in importance by Taemas-Wee Jasper material in settling the debate. All the Gogo placoderms are highly derived while the older NSW material represents fine preservation of much older/primitive forms. Ozraptor4 (talk) 11:47, 14 June 2008 (UTC)
replies: text: Like, concerning how Brindabellaspis' braincase anatomy has more in common with various agnathans?--Mr Fink (talk) 18:06, 14 June 2008 (UTC)
thread_title:  Placoderms and sharks are not sister-groups 

message: This article is well done, but conspicuously omits information that would describe the connections between Placodermi and other lineages of fish.  Contextual information of this kind was what I was looking for.  Janice Vian, Ph.D. (talk) 16:59, 15 November 2012 (UTC)
replies: text: Well, the page is a work in progress, and we need to write in (and source) that the Placoderms are an extinct sister taxon of all other jawed vertebrates, i.e., the group was the first to diverge from the ancestral gnathostomes sometime during the start of the Silurian.  Having said that, the Placoderms left no descendants, having all died out by the very end of the Devonian.--Mr Fink (talk) 17:08, 15 November 2012 (UTC)
replies: text: Current thinking is that placoderms left two groups of descendents, bony fishes and spiny sharks, and that regular sharks are descended from the spiny variety (see Acanthodii#Taxonomy and phylogeny). Placodermi is now viewed as the basal evolutionary grade of gnathostomes. Zyxwv99 (talk) 00:47, 13 September 2016 (UTC)
thread_title:  Descendants of this group of species? 

message: Here's another issue. Should the drawing of Coccosteus decipiens, used as the basis for the anatomy diagram, have an anal fin? --Epipelagic (talk) 08:01, 23 February 2013 (UTC)
replies: text: Yes, as fossils of C. decipiens clearly show an anal fin.  (i.e., the spot underneath the posterior end of the dorsal fin)--Mr Fink 14:04, 23 February 2013 (UTC)
replies: text: The drawing of a Coccosteus on page 32 of Palmer's Dinosaurs and Prehistoric Animals has no anal fin. Nor do these depictions show an anal fin:  (Fig. 271),  and . If you search on "anal fin" in this rather dated book you will find comments such as: "Agassiz in his restored figure has represented... a dorsal and anal fin situated opposite each other... there is no anal fin in Coccosteus...  It is this peculiar lengthening of the haemapophyses under the dorsal... which has evidently given rise to the old idea of the presence of an anal fin... though M'Coy had previously strongly doubted the existence of an anal fin in Coccosteics, Pander's figure has been copied into almost every text-book... the anal fin is also mentioned as present by Zittel in his handbook. M'Coy was, however, correct — there is no anal fin in Coccosteus". --Epipelagic (talk) 08:51, 25 February 2013 (UTC)
replies: text: You're right: After checking Denison's book, I realize I keep confusing the postanal plate with the anal fin.  How embarrassing.  Should we modify the picture, then?--Mr Fink 15:19, 25 February 2013 (UTC)
replies: text:  I've modified it. Don't be embarrassed, I get thing wrong too. --Epipelagic (talk) 05:35, 26 February 2013 (UTC)
thread_title: Anatomy diagram

message: The deleted part says "The males reproduced by inserting a long clasper, the basipterygium that was fused to part of the pelvic girdle." This is no longer correct, as the new link explains in the article: "Unlike the claspers of modern sharks and rays that are a part of the paired pelvic fins, the claspers and female basal plates in placoderms were not at all connected to that fin."
Neither are they no longer considered the sister group to all jawed vertebrates, but their direct ancestors, as mentioned in the article about Gnathostomata. 84.210.10.52 (talk) 13:07, 29 June 2014 (UTC)
replies: text: Technically speaking, a taxon can be regarded as the sister taxon to its direct descendant daughter taxa.--Mr Fink (talk) 20:01, 29 June 2014 (UTC)
thread_title: Claspers

message: The article included the claim that ptyctodontids are paraphyletic with respect to the gnathostome crown. This wasn't something I've seen claimed before so I looked into the cited source; but it's an article about acanthodians. There is a gnathostome phylogeny presented there, but it finds ptyctodontids as the monophyletic sister group to crown-Gnathostomata + Entelognathus. For now I've removed the claim as a probable mistake.Kaficek (talk) 12:47, 1 January 2017 (UTC)
replies: text: My edited was reverted, and so I thought I'd reiterate here why I changed it. The phylogeny in the cited source shows three petalichthyids only (Austroptyctodus, Rhamphodopsis and Campbellodus). They are recovered as a monophyletic group; as are crown gnathostomes. They are not paraphyletic with respect to anything; and I can find no support for a paraphyletic Petalichthyidae anywhere in the literature.Kaficek (talk) 20:45, 6 March 2017 (UTC)
replies: text: Ptyctodontids/Ptyctodontidae/Ptyctodontida, you mean.--Mr Fink (talk) 04:21, 12 March 2017 (UTC)
thread_title:  Ptyctodontid relationship to crown-gnathostomes 

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thread_title:  External links modified 

message: I wonder if these animals were like lampreys in that they could regenerate body parts bitten off in a fight. E.g.  https://phys.org/news/2019-01-lamprey-regenerates-spinal-cord-oncebut.amp 
   
Lampreys can regenerate whole spinal cordLollipop (talk) 02:17, 4 May 2019 (UTC)
thread_title:  I wonder why the head was protected but not the rest 

message: The External anatomy of the placoderm Coccosteus decipiens diagram depicts an armored head with external bones and a "naked" body. This is inaccurate as placoderms did indeed have external integument on their heads--unlike ostracoderms, it's more than likely they didn't just have bones on the outside of their heads and no skin. Entelognathus (talk) 17:50, 16 March 2021 (UTC)
replies: text: I though fossils of Coccosteus showed that the posterior half of the body had no scales.--Mr Fink (talk) 18:28, 16 March 2021 (UTC)
thread_title: ''Coccosteus'' anatomy diagram lacks proper integument

message: Is the citation to Li et al. (2021) in the introduction correct? Where in that paper does it offer a rebuttal to King et al. (2016), and how does it solidy the paraphyletic status of placoderms? These things are not explicitly mentioned in the paper. Bohiggin (talk) 14:05, 28 December 2021 (UTC)
thread_title:  Transitional Taxa 

message: This paper seems to describe a placoderm from Carboniferous deposits https://www.biodiversitylibrary.org/bibliography/15102 Bubblesorg (talk) 19:30, 21 October 2022 (UTC)
replies: text: That paper is from 1855, though. A more recent source would be nice. The Evolution of fish page looks like it has some good sources. Cougroyalty (talk) 20:14, 21 October 2022 (UTC)
replies: text:  Yeah, thanks\. I will take a look--Bubblesorg (talk) 18:53, 22 October 2022 (UTC)
thread_title:  Carboniferous Placoderms?