Talk:Chordate

message: There are some soft constraints that separate Chordata from other biological lineages, but have not yet been made part of the formal definition. 
* Pigmentation : Chordata are not capable of blue pigmentation, that is to say blue skin pigmentation. Blue skin pigmentation is not to be confused with the biological alteration of (for example) feathers in birds -- that appear blue via an evolved prism mechanism in the feather structure.
There still is a lot of differential (DNA sequence based) comparison research going on that is trying to separate out the simplest forms of chordata. As around 90% of the species on Earth don't have a backbone like chordata. Some of these species may have lost their chordata like structures over time and this complication continues to complicate the complete definition of Chordata.
Eyreland (talk) 03:04, 10 September 2016 (UTC)
replies: text: Good point, I have removed it as unsourced, and contradicted by many creatures. --Jules (Mrjulesd) 02:20, 13 March 2017 (UTC)
thread_title:  Pigment & Differential Biology 

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thread_title:  External links modified 

message: The cladogram under phylogeny is so full of problems that it should be edited or removed: Condrychthyes is missing! Sarcopterygii appears to be a synonym of Tetrapods!  — Preceding unsigned comment added by Gabe Lemag (talk • contribs) 17:33, 5 March 2018 (UTC)
replies: text: I agree that is could be improved, but I oppose removal. The Chondrichthyes could be included; the Sarcopterygii gave rise to the tetrapods (plus a few odd fish such as the coelacanths and lung-fish) and this is consistent with the cladogram. --Jules (Mrjulesd) 17:46, 5 March 2018 (UTC)
thread_title:  Cladogram 

message: In the classification section, Cephalochordata is listed with Acraniata in brackets behind it. Haeckel's 1866 Acrania is considered synonymous with Cephalochordata according to its page (though it is also shown on a specific internal branch of the tree of that page, which is a problem all of its own), but I am not sure of the taxonomic history of Acraniata. The Acraniata page is a redirect to Invertebrate, whereas Acrania page is for the developmental defect by the same name (not linked here to spare the reader some pretty graphic imagery). There seems to be some chaos here that needs to be straightened out. Can we remove the piece in brackets, as Cephalochordata is simply the most accepted name right now? Or does it have some greater historical significance of which I am unaware? Dr Mark D. Scherz 08:31, 9 April 2021 (UTC)
replies: text: My understanding is that Acraniata is a historic group of organisms without a distinct cranium. As such it would include Cephalochordata, Hemichordata and Urochordata, which makes it paraphyletic with respect to Craniata. I don't think it should be used as a synonym of Cephalochordata. —  Jts1882 | talk  09:02, 9 April 2021 (UTC)
replies: text:  However, Benton's Vertebrate Palaeontology does list "Cephalochordata (Acraniata)" (p433) and is the source cited for the listing. Nelson's Fishes of the World has a section "Subphylum Cephalochordata (Acrania, in part)" (p16).  —  Jts1882 | talk  09:31, 9 April 2021 (UTC)
thread_title:  Cephalochordata: (Acrania) or (Acraniata) or nix the lot?