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Do I really have to explain myself here for what I'm trying to say? if so , then I will: The Reason why I consider this to be important enough to be here is because of how many people belive Arkarua To be the ancestor of all echinoderms. In simple worlds, that isn't possible. In Complex Words: Arkarua Is Not At all An Echinoderm , Because For one, the first Ever Echinoderm Proven To Be An Echinoderm Was Symmetric And Did not Have Five Way or Radial Symmetry at all, That Echinoderm being Ctenoimbricata. Arkarua (in the image itself) IS Shown to posses 5-way Radial Symmetry , Such As Star Fish Or sea urchins, It Would Be impossible For An Animal With 5-way Radial Symmetry To have Bilateral Symmetry all of a sudden, Especially since It Doesn't look Like it even Evolved into Ctenoimbricata , Especially When it Looks Like A Relative Of A Creature Similar To it Such as Aspidella. Oh yeah , it also lacks The Soft , Spongy Material called stereom , especially When people call It "the earliest echinoderm".
I Am Simply Stating That it's Truly Impossibly For Arkarua to be The ancestor Of all echinoderms, If you Really Do Think that It is , I would Rather Appreciate That someone Edits this Page To add A List Of Reasons Why and Why not Arkarua is And isn't An Echinoderm. — Preceding unsigned comment added by Rugoconites Tenuirugosus (talk • contribs) 22:30, 29 January 2022 (UTC)[reply]
I wonder why this user is taking to such polemic language. The Question is not so absurd at all. The problem is complex, since undisputed echinoderms occur in the early middle cambrian in a wide diversity such as [Gogia], [edioasteroids], [helicoplacoids]. Some researchers propose that [Ctenocystoida] such as the early [Ctenoimbricata] are ancestral to echinodermata, mainly because of their approximate bilateral symmetry. The wide diversity strongly suggests that echinoderms already had a long history of evolutionary diversification in the early middle cambrian.
There are strong arguments that the ctenocystoids belong to the [Blastoza] and have secondarily lost the pentameral structure like other so-called [homalozoans].[1].
Thus, approximate bilateral symmetry of Ctenocystoida is not a strong argument per se, especially since even present echinoderms have bilaterally symmetric larvae and only get their pentameral radial structure as adults.Marci68 (talk) 12:14, 26 March 2023 (UTC)[reply]
References
^David, Bruno and Lefebvre, Bertrand and Mooi, Rich and Parsley, Ronald (2000). "Are Homalozoans Echinoderms? An answer from the extraxial-axial theory". Paleobiol. 26 (4): 529–555. doi:10.1666/0094-8373(2000)026$<$0529:aheaaf$>$2.0.co;2.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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