tag:blogger.com,1999:blog-5519292617097628087.post5236897536301312588..comments2024-01-02T16:09:12.886-07:00Comments on Chinleana: Dinosauria vs. Pseudosuchia - New paper in ScienceBill Parkerhttp://www.blogger.com/profile/05941940882532354219noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-5519292617097628087.post-32612641275381457272008-09-18T11:17:00.000-07:002008-09-18T11:17:00.000-07:00There is more discussion of the Cretaceous dicynod...There is more discussion of the Cretaceous dicynodont over at <A HREF="http://dracovenator.blogspot.com/2008/09/last-dicynodont.html" REL="nofollow">Dracovenator</A>, Adam Yates' blog.220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-22786276760531592602008-09-12T16:32:00.000-07:002008-09-12T16:32:00.000-07:00>The key would be to compare Rare >Earth Ele...>The key would be to compare Rare >Earth Element (REE) signatures of >the matrix around the fossil to >the nearby Cretaceous rocks, as >well as potential Triassic source >rocks. As far as I'm aware, no >one has done this.<BR/><BR/>This should work. An excellent idea.Bill Parkerhttps://www.blogger.com/profile/05941940882532354219noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-38873203780862878622008-09-12T14:25:00.000-07:002008-09-12T14:25:00.000-07:00Everyone I've talked to is happy with the specimen...Everyone I've talked to is happy with the specimen being a dicynodont, but they're all very skeptical of its provenance.<BR/><BR/>There is locality info for the specimen, but the issue is that it was found as float, not in situ. The authors argued that because that area of Australia has Cretaceous bedrock for miles around, the specimen should be Cretaceous. The problem is that Australia is very flat and deeply weathered. Some land surfaces have been exposed since the Miocene! So, the specimen could have eroded out of Triassic rocks quite a long time ago, and then just sat around on or near the land surface for literally millions of years.<BR/><BR/>The key would be to compare Rare Earth Element (REE) signatures of the matrix around the fossil to the nearby Cretaceous rocks, as well as potential Triassic source rocks. As far as I'm aware, no one has done this.<BR/><BR/>For those wondering, the reference is:<BR/><BR/>Thulborn, T., and S. Turner. 2003. The last dicynodont: an Australian Cretaceous relict. <I>Proceedings of the Royal Society of London, Biological Sciences</I> 270:985-993. DOI: <A HREF="http://dx.doi.org/10.1098/rspb.2002.2296" REL="nofollow">10.1098/rspb.2002.2296</A>220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-39441230186584369922008-09-12T12:13:00.000-07:002008-09-12T12:13:00.000-07:00There is a purported Cretaceous dicynodont from Au...<I>There is a purported Cretaceous dicynodont from Australia, but this is based on scrappy material and to be cliche "extraordinary claims require extraordinary evidence" and it is just not there IMHO (see my earlier Polish Dragon post for the citation).</I><BR/><BR/>IIRC, there was a suspected locale that the material came from. Has anyone followed up with that? Or tried to? Ir realize funding is short, but that would be quite a feather in someone's cap if they confirmed the find with more material.Will Bairdhttps://www.blogger.com/profile/07562404098136557872noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-78848444288716376602008-09-11T23:52:00.000-07:002008-09-11T23:52:00.000-07:00Zach - I wouldn't be so hasty to attribute Lystro'...Zach - I wouldn't be so hasty to attribute Lystro's survival to random dumb luck. Recent FEA work comparing Lystro to a more standard Permian dicynodont (can't remember which) shows that it had a much stronger, stiffer skull which was thought to be an adaptation to eating much tougher vegetation, probably horsetails. One thing about the exceedingly poor plant fossil record from the Early Triassic is that horsetails are about all you can find. So speculative as it might be, it seems to me to be a plausible idea that reason for Lystrosaurus' success is that its food formed the dominant vegetation in the wake of the P-Tr event.<BR/>Also Lystosaurus was not the sole dicynodont survivor. There were at least two emydopoid survivors represented by Myosaurus and Kombuisia. The late Permian Vivaxosaurus is also more closely related to Triassic Kannemeyeriformes than to Lystrosaurus indicating that this clade also had to have had at least one surviving lineage crossing the P-Tr boundary.Adam Yateshttps://www.blogger.com/profile/03046084686097124394noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-70018007107828422992008-09-11T22:22:00.000-07:002008-09-11T22:22:00.000-07:00Will,The article is simply providing more evidence...Will,<BR/><BR/>The article is simply providing more evidence against the idea of competition, but unfortunately not really offering a new hypothesis as the conclusions again were that the dinosaurs were "lucky beneficiaries" of another group's misfortune. Still I would not quite put the paper in the cateory of "flogging the hobby horse" because it offers a new approach and some new data. I'll admit that I've been going back and forth with this myself.<BR/><BR/>There is a purported Cretaceous dicynodont from Australia, but this is based on scrappy material and to be cliche "extraordinary claims require extraordinary evidence" and it is just not there IMHO (see my earlier Polish Dragon post for the citation).Bill Parkerhttps://www.blogger.com/profile/05941940882532354219noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-77626508064732199102008-09-11T14:33:00.000-07:002008-09-11T14:33:00.000-07:00ok, time for less delicacy. I was trying to be po...ok, time for less delicacy. I was trying to be polite about this, but...<BR/><BR/>does this constitute 'proof' or merely flogging a hobby horse?<BR/><BR/>sorry, too tired to phrase it nicely.Will Bairdhttps://www.blogger.com/profile/07562404098136557872noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-27475829369122403792008-09-11T14:27:00.000-07:002008-09-11T14:27:00.000-07:00Even at the Hayden Quarry, dinosaurs are still not...Even at the Hayden Quarry, dinosaurs are still not as abundant as pseudosuchians. We've found alot of dinosaur specimens, but they represent a fraction of the total number of specimens excavated.<BR/><BR/>Zach - I agree with Bill in cautioning people about the influence of a Carnian-Norian extinction event on the rise of dinosaurs. With all the new constraints on the Late Triassic timescale, it seems like the evidence for such an extinction is very weak. That of course doesn't rule out the influence of an extinction at the Triassic-Jurassic boundary.<BR/><BR/>Will - You are correct that Benton's idea was a <I>lack</I> of competition. So, I'm not sure why you're confused. The new paper supports this idea, as does Irmis et al. 2007 (in <I>Science</I> last year). However, as Bill points out, competition vs. lucky break is not a simple dichotomy - there are many other options that have yet to be ruled out.220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-12971168350540214122008-09-11T13:32:00.000-07:002008-09-11T13:32:00.000-07:00I know I am going to state this wrong, so forgive ...I <I>know</I> I am going to state this wrong, so forgive me as I do it, but isn't it Benton's pet idea that faunas don't out compete each other, but rather they have been the beneficiaries of mass extinction events for some time?<BR/><BR/>It gives the impression that he doesn't "like" competition much as reasons for faunal replacement at all.<BR/><BR/>Also wasn't there a Cretaceous dicynodont found in Oz none-too-long ago?Will Bairdhttps://www.blogger.com/profile/07562404098136557872noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-29966868388482803812008-09-11T12:23:00.000-07:002008-09-11T12:23:00.000-07:00I'm not so surprised that dinosaurs "lucked out." ...I'm not so surprised that dinosaurs "lucked out." It happens a lot in mass extinctions. Dicynodonts died out in the Permio-Triassic extinction except for <I>Lystrosaurus</I>, who shows no obvious adaptations to make it through unharmed. Neornithine birds survived the KT extinction while Enantiornithines were wiped out. <BR/><BR/>And this is the part where I beg for a copy of the paper in electronic form. ;-) I won't be able to get my hands of a physical copy of the new Science for at least a week (our university library has a terrible lag time).Zachhttps://www.blogger.com/profile/08692080707969333711noreply@blogger.com