tag:blogger.com,1999:blog-5460788270738656369.post3914103106786857495..comments2023-12-24T07:02:43.274+08:00Comments on Catalogue of Organisms: Blinding Me with ScienceChristopher Taylorhttp://www.blogger.com/profile/11075565866351612441noreply@blogger.comBlogger13125tag:blogger.com,1999:blog-5460788270738656369.post-86698437886736652072009-02-20T07:45:00.000+08:002009-02-20T07:45:00.000+08:00Perhaps, but did you know that aquatic ropens suff...Perhaps, but did you know that aquatic ropens suffer terribly from the depredations of parasitic <I>Hallucigenia</I>?Christopher Taylorhttps://www.blogger.com/profile/11075565866351612441noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-9854850557966618282009-02-20T04:38:00.000+08:002009-02-20T04:38:00.000+08:00If you tire of the T. rex survival comparison, you...If you tire of the <I>T. rex</I> survival comparison, you can always use pterosaurs instead. By choosing a variety that disappeared at the right time, you can calibrate your comparison precisely. That alternative offers the added fillip of needling those people who insist that some <I>really are</I> still around, and you get to mention ropens.Unknownhttps://www.blogger.com/profile/00831355954619691739noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-91717057361367083482009-02-10T16:22:00.000+08:002009-02-10T16:22:00.000+08:00Christopher Taylor--Thanks for your comments on my...Christopher Taylor--<BR/>Thanks for your comments on my (ignorant) comments. ... As for legs on an Anomalocaris, I suspect I was remembering a picture of Parapeytoia, as at<BR/>http://www.trilobites.info/species2.html<BR/>though these legs seem to be more like standard arthropod legs than like lobopod appendages.Allen Hazenhttps://www.blogger.com/profile/05098575774774203097noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-22309149219535758642009-02-09T15:10:00.000+08:002009-02-09T15:10:00.000+08:00Schinderhannes seems to have derived traits behind...<I>Schinderhannes seems to have derived traits behind the head, while the head (stalked eyes, circular mouth, "anomalocaridiform" great appendage) is stunningly plesiomorphic.</I><BR/><BR/>It's slightly more complicated, as <I>Schinderhannes</I> is also coded as having an arthropod-like carapace over the head, which <I>Anomalocaris</I> lacks. But yes, the majority of the head does look more plesiomorphic than the body.<BR/><BR/>And something I've just remembered - <A HREF="http://ediacaran.blogspot.com/2008/10/spandrels-of-san-marco-and-anomalocaris.html" REL="nofollow">Chris Nedin</A> wrote a post a little while back where he hypothesised that anomalocarids became extinct because of the evolution of enrollment in trilobites at the end of the Cambrian. Anomalocarid-grade animals in the Devonian rather puts the kybosh on that idea, doesn't it?<BR/><BR/><I>And haven't I seen a relatively recent (within the past decade) report that Anomalocaris itself had a series of little lobopod-like limbs sticking down between the "flaps" on each side?</I><BR/><BR/>As far as I know, there's no direct evidence for leg morphology in <I>Anomalocaris</I> (and the <I>Schinderhannes</I> paper has a bit of dodgy coding for <I>Anomalocaris</I> in that regard). But another anomalocarid-grade animal, <I>Kerygmachela</I>, does have preserved lobopod limbs. Going by the results of the <I>Schinderhannes</I> analysis, with <I>Anomalocaris</I> above <I>Kerygmachela</I> but below <I>Schinderhannes</I>, it's an open question whether or not <I>Anomalocaris</I> had lobopod limbs or more arthropod-like limbs.Christopher Taylorhttps://www.blogger.com/profile/11075565866351612441noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-58586552316775363902009-02-09T14:31:00.000+08:002009-02-09T14:31:00.000+08:00Christopher Taylor--No, you understood me corectly...Christopher Taylor--<BR/>No, you understood me corectly, and I wasn't thinking very clearly: I was just bowled over by the "primitive" aspect of the head-end of the critter.<BR/>----<BR/>A cladogram represents a hypothesis, not just about genealogical relations, but about the order in which novel traits appeared. Comparing Schinderhannes, Anomalocaris, and the "Great Appendaged Euarthropods," the current one suggests that evolutionary novelty, here, started from the tail: Schinderhannes seems to have derived traits behind the head, while the head (stalked eyes, circular mouth, "anomalocaridiform" great appendage) is stunningly plesiomorphic.<BR/>---<BR/>And haven't I seen a relatively recent (within the past decade) report that Anomalocaris itself had a series of little lobopod-like limbs sticking down between the "flaps" on each side?Allen Hazenhttps://www.blogger.com/profile/05098575774774203097noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-37669803919062745542009-02-08T08:57:00.000+08:002009-02-08T08:57:00.000+08:00It's possible that I've misunderstood what you're ...It's possible that I've misunderstood what you're suggesting (in which case, I apologise), but I fail to see what the problem is. Not all parts of an organism change at the same rate over evolution, so it shouldn't be surprising when some features of an organism look more plesiomorphic than others.<BR/><BR/>That said, the data matrix for the <I>Schinderhannes</I> analysis is a little rudimentary, and possibly wouldn't be the worse off for a few extra characters.Christopher Taylorhttps://www.blogger.com/profile/11075565866351612441noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-33725918685252450552009-02-07T16:17:00.000+08:002009-02-07T16:17:00.000+08:00The front end is just TOO Anomalocaridid-like...Ju...The front end is just TOO Anomalocaridid-like...<BR/>Just how well DO we know what Anomalocaris's appendages were like? Enough to refute the "backwards" hypothesis?<BR/>"Backwards" hypothesis that occurs to my suspicious mind): <BR/>Schinderhannes (give or take the "wings") is actually a late surviving "stem anomalocaridarthropod," morphologically similar to the common ancestor of A. and A.: the line leading to Anomalocaris LOST its sclerotized tergites as it increased in size.<BR/>---<BR/>Sorry. Amateur's comments, without having gone through the data matrix AT ALL. Disregard. ...<BR/>I just find the conservation of great appendage and mouth morphology through a period in which so many euarthropd features evolved... incredible?Allen Hazenhttps://www.blogger.com/profile/05098575774774203097noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-88050092314729710122009-02-07T10:53:00.000+08:002009-02-07T10:53:00.000+08:00Schinderhannes the bandit, BTW, has an English wik...<I>Schinderhannes the bandit, BTW, has an English wikipedia page</I><BR/><BR/>As does the fossil <I>Schinderhannes</I>. Already. Though I must say, Schinderhannes the person doesn't really sound like someone I'd want to honour with a patronym.<BR/><BR/><I>I thought ancestral arthropods were supposed to look like velvet worms (coincidentally mentioned in the "Incredible Organisms" thread). Or is that for an earlier stage?</I><BR/><BR/>Yep, go back a bit further for the lobopods. You can see one of the Cambrian lobopods - <I>Aysheaia</I> - at the root of the phylogenetic tree.Christopher Taylorhttps://www.blogger.com/profile/11075565866351612441noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-85296019156287356232009-02-07T03:15:00.000+08:002009-02-07T03:15:00.000+08:00Man!I thought ancestral arthropods were supposed t...Man!<BR/><BR/>I thought ancestral arthropods were supposed to look like velvet worms (coincidentally mentioned in the "Incredible Organisms" thread). Or is that for an earlier stage?Mike Keeseyhttps://www.blogger.com/profile/00147156174467903264noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-41328468937163246082009-02-06T23:26:00.000+08:002009-02-06T23:26:00.000+08:00Damn, and I was thinking this would be a quiet wee...Damn, and I was thinking this would be a quiet weekend (aside from the Ocean Bowl), one I could use to catch up on honey dew lists! <BR/><BR/>When I saw the image I first thought it was a new reconstruction or artist interpretation of <I>Anomalocaris</I>. This is very exciting.Eric Heupelhttps://www.blogger.com/profile/18327896268176961009noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-22895197503323677092009-02-06T22:28:00.000+08:002009-02-06T22:28:00.000+08:00Schinderhannes the bandit, BTW, has an English wik...Schinderhannes the bandit, BTW, has an English wikipedia page: http://en.wikipedia.org/wiki/SchinderhannesAndreas Johanssonhttps://www.blogger.com/profile/08802392912541974977noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-53682057207872012082009-02-06T18:35:00.000+08:002009-02-06T18:35:00.000+08:00I suppose anomalocarids are insufficiently sclerot...<I>I suppose anomalocarids are insufficiently sclerotized to fossilize easily?</I><BR/><BR/>'Fraid so. The hardest parts (and then still not particularly hard) are the ring of tooth-plates and the great appendages, both of which were described as separate entire or near-entire organisms before being recognised as part of one larger organism.<BR/><BR/>An even more remarkable case would be <I>Bowengriphus</I> from the Permian, which was described as closely related to <I>Odontogriphus</I> that had been only known from the Cambrian. Not everyone accepts that <I>Bowengriphus</I> is an odontogriphid, though.Christopher Taylorhttps://www.blogger.com/profile/11075565866351612441noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-58403088555090723812009-02-06T17:11:00.000+08:002009-02-06T17:11:00.000+08:00Neat.It's sobering to think what gaps our knowledg...Neat.<BR/><BR/>It's sobering to think what gaps our knowledge of paleozoic life still has. I suppose anomalocarids are insufficiently sclerotized to fossilize easily?Anonymousnoreply@blogger.com