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Cephalization and Bilateria

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Why is cephalization such a common characteristic of bilaterians but seems to be entirely absent in animals with radial symmetry? What is it about the evolution of cephalization that seemingly doesn't support well a radially symmetric body plan? Momin Geoffrey (talk) 21:02, 26 January 2025 (UTC)[reply]

The article explains this quite clearly. If you habitually move in the direction of one end of your body, that end becomes the front, and can't help meeting the world first, so senses and mouth are needed to identify and process it. If you're a round jellyfish and move in any direction, you don't have a front, so it doesn't happen. Chiswick Chap (talk) 21:28, 26 January 2025 (UTC)[reply]
Thank you Momin Geoffrey (talk) 21:35, 26 January 2025 (UTC)[reply]


GA review

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This review is transcluded from Talk:Cephalization/GA1. The edit link for this section can be used to add comments to the review.

Nominator: Chiswick Chap (talk · contribs) 13:52, 16 December 2024 (UTC)[reply]

Reviewer: RoySmith (talk · contribs) 17:01, 19 February 2025 (UTC)[reply]


Starting review...

Many thanks! I'll respond promptly to any comments. Chiswick Chap (talk) 17:16, 19 February 2025 (UTC)[reply]

I'll be spot-checking citations [5, 6, 8, 10, 13] from Special:Permalink/1272139696.

  • I'm unable to find Godfrey-Smith, Peter (2017). Other Minds: The Octopus and the Evolution of Intelligent Life. HarperCollins Publishers. p. 38. ISBN 978-0-00-822628-2, could you please send me a copy of that (just the one page that you cited). Thanks.

I originally left this on the talk page, but now that I'm doing a full review, moving it here

  • The lead sentence says Cephalization is an evolutionary trend in animals that, over many generations .... That's not incorrect, but "many generations" to me sounds like 10's or 100's. For example, in my own lifetime, I've noticed a lot more black squirrels in New York. That's a phenomenon which has evolved over "many generations of squirrels". But here we're talking about, I don't know, millions of generations? 100's of millions? Calling that "many" doesn't seem to give the right inference.
    • Edited to a "sufficient number of generations".
  • These groups, however, are not closely related: in fact, they represent widely separated branches of the Bilateria, as shown on the phylogenetic tree; their lineages split hundreds of millions of years ago. Other (less cephalized) phyla are not shown, for clarity.[7][8][9] the URL in [9] links to some malware-infested domain parking site.
    • Archived [9].
  • Also, would it be possible to split [7] and [8] into distinct citations, each to the particular statement they support?
    • They're already citing a single sentence.
  • The same applies to the [5][6] pair in the previous sentence, but no so much of a problem there because one of those is a single page and thus easier to search.
  • Cephalopod molluscs including octopus, squid, cuttlefish and nautilus are the most intelligent and highly cephalized invertebrates, with well-developed senses, including advanced 'camera' eyes and large brains.[10][11] I'm unable to find most (any?) of this in [10]. It's possible that it's in [11] but as with the previous sections, splitting this into two citations would be a big help.
  • Cephalochordates like the lancelet, a small fishlike animal with very little cephalization, are closely related to vertebrates but do not have these structures. In the 1980s, the new head hypothesis proposed that the vertebrate head is an evolutionary novelty resulting from the emergence of neural crest and cranial placodes (thickened areas of ectoderm), which result in the formation of all senses outside of the brain.[12][13] I found most of this in [13], but not all. I don't see any mention of the lancelet, for example. Perhaps it's in [12]? I downloaded a copy of [12] from JSTOR, but fie on them for exporting the PDF in a non-searchable format. I've skimmed the paper, but don't see anything about lancelets there either.
  • Cephalization in vertebrates, the group that includes mammals, birds, reptiles, amphibians and fishes, has been studied extensively.[4] The heads of vertebrates are complex structures, with distinct sense organs for sight, olfaction, and hearing, and a large, multi-lobed brain protected by a skull of bone or cartilage. has a {{citation needed}}
    • Cited.

Work on the citations and I'll pick up when you've got all that sorted. RoySmith (talk) 18:16, 19 February 2025 (UTC)[reply]