tag:blogger.com,1999:blog-3618628476414479312.post7142677298689220098..comments2023-11-05T04:41:29.920-08:00Comments on Dracovenator: Jumping the gun: SimilicaudipteryxAdam Yateshttp://www.blogger.com/profile/03046084686097124394noreply@blogger.comBlogger18125tag:blogger.com,1999:blog-3618628476414479312.post-87486991624365370132008-09-05T12:10:00.000-07:002008-09-05T12:10:00.000-07:00I don't think we can expect to have found a pygost...I don't think we can expect to have found a pygostyle in the Falcarius quarry by now if it were present. There are plenty of bones which aren't represented yet- nasals, parietals, jugals, surangulars, sterna, furculae, etc.. A Beipiaosaurus-type pygostyle would be small anyway.<BR/><BR/>Yes, the Tropic Shale Nothronychus sp. preserves 22 caudal vertebrae. Not sure if it's the whole series or not.Mickey Mortimerhttps://www.blogger.com/profile/08831823442911513851noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-65045252502337282902008-09-05T09:12:00.000-07:002008-09-05T09:12:00.000-07:00Mickey said:"While there isn't any evidence of a p...Mickey said:<BR/><BR/>"While there isn't any evidence of a pygostyle in Falcarius, there isn't any evidence of it being pygostyle-less either."<BR/><BR/>I wouldn't quite say that. There isn't anything unambiguously <I>Falcarius</I> that would prove/disprove the presence/absence of a pygostyle. Still, based on the fact that there is only evidence for one theropod in the size class of <I>Falcarius</I> in the Crystal Geyser Quarry, and the relative abundance of these remains, I'd say that there is circumstantial evidence it didn't have a pygostyle.<BR/><BR/>"And as no therizinosaurs are known which lack a pygostyle, being pygostyle-less is not the default position."<BR/><BR/>Fair enough. Does the Tropic Shale therizinosaur have caudals?220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-51871541678669854292008-09-04T23:54:00.000-07:002008-09-04T23:54:00.000-07:00Xu et al. (2003) is all the published information ...Xu et al. (2003) is all the published information we have on the specimen, so we just have to take their word for it that it's part of the holotype. It certainly seems to be a basal therizinosaur.<BR/><BR/>While there isn't any evidence of a pygostyle in Falcarius, there isn't any evidence of it being pygostyle-less either. And as no therizinosaurs are known which lack a pygostyle, being pygostyle-less is not the default position.Mickey Mortimerhttps://www.blogger.com/profile/08831823442911513851noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-79102784103692608602008-09-03T17:23:00.000-07:002008-09-03T17:23:00.000-07:00Thanks - I just got a PDF of the Xu et al. 2003 pa...Thanks - I just got a PDF of the Xu et al. 2003 paper. How clear is it that this specimen belongs to the holotype? They only say that they re-excavated the same "quarry".<BR/><BR/>You are right about the disarticulated <I>Falcarius</I> material, but one could say that right now there isn't any evidence for a pygostyle in that taxon.<BR/><BR/>Has anyone compared the morphology of pygostyles across taxa to see how similar they are?220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-36388965552817477292008-09-03T16:54:00.000-07:002008-09-03T16:54:00.000-07:00Falcarius doesn't necessarily lack a pygostyle. R...Falcarius doesn't necessarily lack a pygostyle. Remember the skeletal reconstruction is based on numerous disarticulated specimens, which may not include the distalmost caudal vertebrae. We won't know until Zanno's paper on Falcarius' axial skeleton comes out. For Beipiaosaurus' pygostyle, the ref is-<BR/><BR/>Xu, Cheng, Wang and Chang, 2003. Pygostyle-like structure from Beipiaosaurus (Theropoda, Therizinosauroidea) from the Lower Cretaceous Yixian Formation of Liaoning, China. Acta Geologica Sinica, v. 77, n. 3, p. 294-298.Mickey Mortimerhttps://www.blogger.com/profile/08831823442911513851noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-2822485001929671032008-09-03T11:47:00.000-07:002008-09-03T11:47:00.000-07:00What is the reference for Beipiaosaurus having a p...What is the reference for <I>Beipiaosaurus</I> having a pygostyle? I was not aware that it did. Regardless, <I>Falcarius</I> (Kirkland et al. 2005) is currently the most basal therizinosauroid, and it lacks a pygostyle. Even if the presence of a pygostyle optimized at the base of oviraptorosaurs, therizinosaurs, or Oviraptorosauria + Therizinosauria, I still don't think its strong support for an avialan position of oviraptorosaurs. Changing the number of caudal vertebrae is really common in modern tetrapods, and I would expect that if all these coelurosaurs have feathers, there's probably some good reasons why multiple lineages would independently evolve a pygostyle.<BR/><BR/>Kirkland, J.I., L.E. Zanno, S.D. Sampson, J.M. Clark, and D.D. DeBlieux. 2005. A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah. <I>Nature</I> 435:84-87. DOI:<A HREF="http://dx.doi.org/10.1038/nature03468" REL="nofollow">10.1038/nature03468</A>220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-47414747106705189732008-09-03T03:59:00.000-07:002008-09-03T03:59:00.000-07:00Regardless of the phylogenetic position of therizi...Regardless of the phylogenetic position of therizinosaurs (I support Senter's most recent analysis that finds therizinosaurs outside the paravian-oviraptorosaur clade), Beipiaosaurus, a basal therizinosaur, has a pygostyle. So, at least this avian-like trait evolved three times in three lines of theropod having relatively shortened tails. On the basis of the avalaible evidence, I interprete the fusion of the distalmost caudals as an homoplastic phenomenon linked to/forced by the reduction of the tail.Andrea Cauhttps://www.blogger.com/profile/10855060597677361866noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-64421512295737894032008-09-02T19:30:00.000-07:002008-09-02T19:30:00.000-07:00Darren - I agree with Adam, the evidence seems ove...Darren - I agree with Adam, the evidence seems overwhelmingly in favor of gavialids as crocodylids. Even though his morphological analyses continue to disagree, I think that if you talk to Chris he will admit that the molecular data is quite convincing. As for mounting molecular evidence, see the latest paper in MPE by Gatsey and colleagues:<BR/><BR/>Gatsey, J., and G. Amato. 2008. The rapid accumulation of consistent molecular support for intergeneric crocodylian relationships. <I>Molecular Phylogenetics & Evolution</I> 48:1232-1237. DOI:<A HREF="http://dx.doi.org/10.1016/j.ympev.2008.02.009" REL="nofollow">10.1016/j.ympev.2008.02.009</A><BR/><BR/>Adam - I think that although there are always limits to the fossil evidence, the available basal oviraptorosaurs DO strongly support their traditional position as basal maniraptorans. See for example <I>Incisivosaurus</I> and <I>Microvenator</I>. Most of the characters used to support an avialan position for oviraptorosaurs are only found within oviraptorids, and do not have a wide distribution within the group. Finally, a variety of analyses support a sister-group relationship between therizinosaurs and oviraptorosaurs; if oviraptorosaurs are avialans, we should expect to see avialan characters in basal therizinosaurs as well. I don't know enough about the morphology of these guys to go any further though :P220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-18011299814036269382008-09-02T01:00:00.000-07:002008-09-02T01:00:00.000-07:00Darren - Yes morphological analysis alone will con...Darren - Yes morphological analysis alone will continue to place gavials in a basal position. What impresses me is the strength of the molecular data (multiple independent genes) and the fact that morphological data (including fossils) are insufficient to overturn this signal in combined analyses. I'm not in the extremist 'molecules trump morphology every time' camp but molecules are an important and rich store of data on the history of organisms and good phylogenetic hypotheses must take them into account (if at all possible). <BR/>Mickey- We might be able to test the hypothesis without molecules if we are able to find more basal oviraptorosaurs.Adam Yateshttps://www.blogger.com/profile/03046084686097124394noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-81295057480988581102008-09-01T10:10:00.000-07:002008-09-01T10:10:00.000-07:00Great point but... 'Gavialoids are crocodylids' is...Great point but... 'Gavialoids are crocodylids' is not the done deal you (and Gatesy <I>et al</I>.) seem to be saying, given that morphological analyses are still finding Gavialoidea to be outside of Brevirostres. Chris Brochu published cladograms showing such last year (<I>Palaeontology</I> 50, 917-928), and as you'll know he is more than familiar with the debate. Hmm.Darren Naishhttps://www.blogger.com/profile/00324870234525004643noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-48393240693956520692008-09-01T02:16:00.000-07:002008-09-01T02:16:00.000-07:00A wholesale reversion may explain the less bird-li...A wholesale reversion may explain the less bird-like morphology of both derived dromaeosaurids and troodontids compared to their more basal relatives: this is supported also by morphological data.<BR/><BR/>I like the hypothesis of an avialan origin for oviraptorosaurs... but the currently known data (unfortunately only morphological, and based only on Cretaceous forms that are more than 20 My younger than the basalmost known eumaniraptorans) support a non-eumaniraptoran status for ovi & co. <BR/><BR/>I've added Similicaudipteryx in my analysis: it results a "basal avimimid", sister-group of a "Avimimus+Nomingia" clade. On the basis of this hypothesis, the pygostylian-like oviraptorosaurs are not a paraphyletic grade of primitive oviraptorosaurs, but a group closely related to oviraptorids that convergently acquired some pygostylian features. The support is low, but it is an interesting alternative to the hypothesis of a closer avialan-oviraptorosaur link.Andrea Cauhttps://www.blogger.com/profile/10855060597677361866noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-75408493741845367962008-08-31T22:36:00.000-07:002008-08-31T22:36:00.000-07:00I'm nothing if not a source of theropod minutia. ;...I'm nothing if not a source of theropod minutia. ;)<BR/><BR/>As Norell and Makovicky (1999) explain, the first dorsal of Deinonychus illustrated by Ostrom has only the broken base of a large hypapophysis. Hence it looks small.<BR/><BR/>As for oviraptorosaur relationships, they very well may be avialans (closer to Passer than Deinonychus). But just as morphological data may not ever give us parsimoniously monophyletic cyclostomes, we may never really know how taxa without preserved genetic material are related.Mickey Mortimerhttps://www.blogger.com/profile/08831823442911513851noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-17121777024618043172008-08-31T07:22:00.000-07:002008-08-31T07:22:00.000-07:00Mickey: Can't slip any theropod anatomical general...Mickey: Can't slip any theropod anatomical generalisations past you can I? I was working from Ostrom's Deinonychus monograph which shows the anterior dorsal hypapophyses as titchy little things. Thanks for the info on greater dromaeosaurid diversity.<BR/><BR/>'Sono.....': I'm not surprised that Oviraptorosaurs came out as basal maniraptors in your analysis, that is after all the most parsimonious solution with the data at hand. My suggestion was just that this MIGHT be a case, like that of gavials and hagfish, where a parsimony analysis is being confounded by wholesale reversion. I also would love to find an 'older-than-jehol' maniraptoran lagerstatte. <BR/>Thanks to everyone who send me a Similicaudipteryx pdf.Adam Yateshttps://www.blogger.com/profile/03046084686097124394noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-68715531168148293182008-08-29T05:05:00.000-07:002008-08-29T05:05:00.000-07:00I agree with you: there's a very interesting grada...I agree with you: there's a very interesting gradation of morphology between Confuciusornithids- Sapeornis/Omnivoropteryx- Jeholornis- Protarchaeopteryx- Caudipteryx- Oviraptorids. I included several oviraptorid-avialan characters in my theropod phylogenetic analysis, but the result does not support a pygostylian status for Oviraptorosauria: it is similar to the phylogeny of Senter (2007).<BR/><BR/>We hope to find new basal maniraptorans (possibly outside the Jehol Biota!)Andrea Cauhttps://www.blogger.com/profile/10855060597677361866noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-36086827422328690612008-08-29T02:56:00.000-07:002008-08-29T02:56:00.000-07:00Who says dromaeosaurids don't have enlarged hypapo...Who says dromaeosaurids don't have enlarged hypapophyses? If we measure their height as a percentage of the posterior centrum height, Similicaudipteryx's largest one is ~34%. Luanchuanraptor has one ~38%, Variraptor has one 64%*, and Rahonavis has one that's over 45% of centrum height. In addition, Utahraptor (Britt et al., 2001), Deinonychus (Norell and Makovicky, 1999) and Saurornitholestes (Currie and Dong, 2001) have been stated as having them, and Buitreraptor, Adasaurus, Velociraptor and Bambiraptor have been coded as having them. In fact, the only dromaeosaurid which lacks large hypapophyses seems to be Microraptor.<BR/><BR/>* And yes, I know Rauhut suggested the paratype anterior dorsal vertebra is a caenagnathid, based on resemblence to Chirostenotes, especially in having two pairs of pleurocoels. Yet Achillobator and Utahraptor both also have two pairs of pleurocoels in some dorsals, and Variraptor resembles Deinonychus more than Chirostenotes in having a longer infraprezygopophyseal fossa, more poorly developed infradiapophyseal fossa, anteroposteriorly narrower neural spine, and basally restricted posterior interspinous ligament groove. The prominent epipophyses also suggest anterior cervical epipophyses would be well developed, as in dromaeosaurids but not oviraptorosaurs.Mickey Mortimerhttps://www.blogger.com/profile/08831823442911513851noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-88396418272569862432008-08-28T11:26:00.000-07:002008-08-28T11:26:00.000-07:00Awesome. Any chance you can send me a PDF of that ...Awesome. Any chance you can send me a PDF of that new oviraptorosaur, brother? I would be forever in your debt!Zachary Millerhttps://www.blogger.com/profile/05035947146927565746noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-78991547923487697612008-08-28T07:49:00.000-07:002008-08-28T07:49:00.000-07:00Thanks for the comments, you can send the pdf to y...Thanks for the comments, you can send the pdf to yatesam at gmail.com, I'd be very gratefull. <BR/>As for the protarchaeopterygids, are they really less pygostylian? The postcranium isn't all that well known and the cranium rather oddly specialised in its own ways. Like I said. I'm just throwing out a thought that has been growing in my mind for some time.<BR/><BR/>AdamAdam Yateshttps://www.blogger.com/profile/03046084686097124394noreply@blogger.comtag:blogger.com,1999:blog-3618628476414479312.post-2125360254552348992008-08-28T04:45:00.000-07:002008-08-28T04:45:00.000-07:00Very interesting post!Given that the currently kno...Very interesting post!<BR/>Given that the currently known basalmost oviraptorosaurs (Incisivosaurus and Protarchaeopteryx)are "less pygostylian-like" and more "basal maniraptoran" in their morphology than caudipterids are, I think oviraptorosaurs and short-tailed avialans acquired their similarities convergently. <BR/>If you need a pdf copy of the Similcaudipteryx paper, I would send you (I need your e-mail address...).Andrea Cauhttps://www.blogger.com/profile/10855060597677361866noreply@blogger.com