tag:blogger.com,1999:blog-5460788270738656369.post8028381788715761725..comments2023-12-24T07:02:43.274+08:00Comments on Catalogue of Organisms: Name the Bug: Polyplacus kilmeriChristopher Taylorhttp://www.blogger.com/profile/11075565866351612441noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-5460788270738656369.post-38833913095413285122010-03-25T06:56:08.466+08:002010-03-25T06:56:08.466+08:00Maybe they rested on their sides?
Helicoplacoids ...<i>Maybe they rested on their sides?</i><br /><br />Helicoplacoids have indeed been suggested to be mobile animals, with the expansion and contraction of the test allowing them to burrow through sediment rather like a modern sea cucumber. The main objection to a mobile helicoplacoid, as far as I know, is that it then becomes hard to explain the spiral ambulacral arrangement.<br /><br /><i>Or maybe they ingested through their anuses?</i><br /><br />But we don't know where the helicoplacoid anus is, either. Or, as Steve asked, the madreporite or anything else (that is, of course, if they had one). The floor plates of the ambulacra in <i>Helicoplacus</i> do have gaps between them that have been interpreted as providing openings for tube feet.<br /><br /><i>suppose that it was like some corals are today, with symbiotic algae that absorbs light and turns it into food?</i><br /><br />Would the heavy armour be problematic in that regard? Not that helicoplacoid feeding isn't problematic otherwise.<br /><br /><i>P.S. I win #14! I get Chris for a day!</i><br /><br />I dunno - buy me a drink and we'll talk about it :-)Christopher Taylorhttps://www.blogger.com/profile/11075565866351612441noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-69801802244014308322010-03-25T06:31:12.233+08:002010-03-25T06:31:12.233+08:00I always wondered about the "sessile" pa...I always wondered about the "sessile" part of this animal. I remember when I first saw a reconstruction of a Helicoplacoid and thought it was an enlarged drawing of a ciliate protist with spiral kineties (sp). <br /><br />- suppose that it was taking advantage of the interim state of the substrate between hard and soft? spiraling through the semi-soft substrate successfully, but being smothered by the fully gushy mud of the cambrian.<br /><br />- alternately suppose that it was like some corals are today, with symbiotic algae that absorbs light and turns it into food? I presume no one has found any sign of a water-vascular system, nor a madreporite, nor anal-pyramid. none would be needed for a photosynthetic symbiotic animal.<br /><br />P.S. I win #14! I get Chris for a day! :DSteveEDhttp://www.zoxesyrbautie.comnoreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-1016850514600901872010-03-25T06:26:58.788+08:002010-03-25T06:26:58.788+08:00I find it hard to believe that any two Cambrian sp...I find it hard to believe that any two Cambrian specimens found at different sites can reasonably be considered conspecific (trilobites notwithstanding).Unknownhttps://www.blogger.com/profile/00831355954619691739noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-55247589040393166562010-03-24T22:37:05.717+08:002010-03-24T22:37:05.717+08:00"this is the most reasonable position in comp...<i>"this is the most reasonable position in comparison to the anatomy of other echinoderms but implies a lateral position for the mouth in the living animal when pretty much all other sessile animals have their mouths positioned dorsally."</i><br /><br />Maybe they rested on their sides?<br /><br /><i>"In contrast, Durham (1993) suggested that the mouth might be located at the upper apex which seems more sensible from a functional perspective, but implies a branching and reversal of direction in the ambulacrum that is completely unlike anything seen in any other echinoderm"</i><br /><br />Or maybe they ingested through their anuses?<br />(I, of course, am talking through mine.)Mike Keeseyhttps://www.blogger.com/profile/00147156174467903264noreply@blogger.com