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"This means their body plans are laid around a longitudinal axis (rostral–caudal axis) with a front (or "head") and a rear (or "tail") end, as well as a left–right–symmetrical belly (ventral) and back (dorsal) surface" does this mean through the median and coronal planes respectively? Dunkleosteus77(talk)22:00, 11 January 2025 (UTC)[reply]
That is implied, depends whether we're thinking axes and surfaces, or dividing planes as our frame of reference.
"parasitic worms have extremely plesiomorphic body structures" a non-apical blob creature being called a worm is kinda weird, maybe just use helminth? Especially because the non-apical, non-worm looking ones are I think usually called flukes Dunkleosteus77(talk)22:00, 11 January 2025 (UTC)[reply]
No. I've removed the parasitic sentence. Given the debate about the urbilaterian in the next section, You're right about roundish vs flattish worms: I've demoted the wormlike animal discussion: that basically applies later, to the Nephrozoa.
I feel like the first para needs a little more historical context since you name everyone involved in making either of the 2 hypotheses, but in the next para you don't. Like there's definitely a big history happening here, it'll just take more than a sentence to explain it properly Dunkleosteus77(talk)22:00, 11 January 2025 (UTC)[reply]
Extended with some more explanation of each side's point of view.
The phrase is purely relative, and as such is perfectly safe: the 21st century (or the end of the 20th) is certainly "more recent" than the 19th. This is nothing like saying "now" or "recently". I don't feel we need dates for these really.
Actually, since there's quite a few ideas on what the urbilaterian looked like, I'm not sure it's the most NPOV to pick a favorite to display in the taxobox, especially since Xenacoelomorpha is the least-speciose branch of bilateria, and this isn't the urbilaterian article. I wonder if a collage or maybe a picture of a bilaterally symmetrical embryo might be more appropriate? Dunkleosteus77(talk)14:39, 13 January 2025 (UTC)[reply]