tag:blogger.com,1999:blog-3248412803814730250.post1735144133633537370..comments2024-03-17T01:48:59.504-07:00Comments on The Theropod Database Blog: Theropod Database Update March 2022 with SVP 2021 thoughtsMickey Mortimerhttp://www.blogger.com/profile/08831823442911513851noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-3248412803814730250.post-86041781719195124382022-04-16T02:20:46.210-07:002022-04-16T02:20:46.210-07:00Thanks for informing me of Martin-Silverstone'...Thanks for informing me of Martin-Silverstone's comments on Piksi maybe being theropod after all. I was unaware of them and need to look into each side's arguments.<br /><br />As for Lacerda et al.'s study, I'm unconvinced by its underlying method's validity. In their morphometric analyses you can always (except for figure 2a) draw a boundary around Suchomimus and Cristatusaurus excluding other taxa. And in their morphometric phylogenetic analyses, I'd like to see a proof of concept before with e.g. Allosaurus or tyrannosaurids because I think premaxillary shape is quite variable within a theropod species. Thus I don't trust characters like "(1) the first premaxillary alveolus of C. lapparenti is more posteriorly positioned on the rostrum; (2) the fourth premaxillary alveolus of C. lapparenti is slightly larger, which is also (3) more spaced from the third premaxillary; (4) the edge of the third premaxillary alveolus is slightly more ventrally placed in C. lapparenti; and (5) C. lapparenti has the posterodorsal region of the premaxilla slightly less expanded, with a less prominent sagittal crest" to be taxonomically significant.<br /><br />Then when it comes to the claimed morphological differences, Lacerda et al. seem to get things wrong. They claim the proposed autapomorphy by Sales and Schultz (2017) was "a very convex secondary palate that extends below the line of the premaxillary teeth, a morphological condition that differs from both Suchomimus tenerensis and Baryonyx walkeri", but the latter paper actually says "This condition is also seen in Oxalaia, Baryonyx, and the African spinosaurines (Fig 4A and 4C), and possibly in Irritator and Angaturama [3,5,28,62]. On the other hand, the convex palate of Suchomimus can only be seen in lateral view through breaks in the referred rostrum MNN GDF501", which makes the Suchomimus paratype the outlier with this potential individual or taphonomic difference from other spinosaurids. Similarly they say "it is recovered as the basalmost<br />taxon due to the absence of crown striations (character 142<br />[0]) and by the presence of premaxillary teeth serrations (character<br />149[0]), two conditions that differ from other spinosaurids (Sales<br />and Schultz 2017)", but the latter paper never claims this (maybe it's scorings in their matrix?). Baryonyx has been described as having serrations on all teeth (Charig and Milner, 1997) and Ceratosuchops explicitly so on premaxillary teeth (Barker et al., 2021). Striations have not been shown to be taxonomically variable in spinosaurids and the premaxilla of Suchomimus (MNN GDF501) seems to lack preserved teeth anyway.<br /><br />So yeah, I'm not convinced.Mickey Mortimerhttps://www.blogger.com/profile/08831823442911513851noreply@blogger.comtag:blogger.com,1999:blog-3248412803814730250.post-7746982378396572952022-04-10T17:32:28.489-07:002022-04-10T17:32:28.489-07:00Cristatusaurus (Lacerda et al. 2021), “Megalosauru...<i>Cristatusaurus</i> (Lacerda <i>et al.</i> 2021), “<i>Megalosaurus</i>” <i>ingens</i> (Soto <i>et al.</i> 2020), <i>Phuwiangvenator</i> (Samathi <i>et al.</i>; these authors also report a proximally wedge-shaped metatarsal III in <i>Cristatusaurus</i>, nullifying one of <i>Chilantaisaurus</i>’ alleged avetheropod characters), Cretaceous avians (Mayr 2022) & <i>Piksi</i> (Martin-Silverstone <i>et al.</i> 2016) also need to be updated.Adamhttps://www.blogger.com/profile/14334710938603889552noreply@blogger.comtag:blogger.com,1999:blog-3248412803814730250.post-4110655176611605722022-03-19T23:42:47.979-07:002022-03-19T23:42:47.979-07:00Mark Norell likes naming dinosaurs after Buddhist ...Mark Norell likes naming dinosaurs after Buddhist deities. Apsaravis ukhaana, Citipati osmolskae, Erketu ellisoni, Beg tse, Shri devi, Kuru kulla... at least the first three had unique specific names. How hard is it to use "Begtseia rugosus", "Shridevi macronychus", or "Airakoraptor kurukullae"?Anonymoushttps://www.blogger.com/profile/10795877970542539791noreply@blogger.comtag:blogger.com,1999:blog-3248412803814730250.post-32896466511443831802022-03-17T03:36:39.017-07:002022-03-17T03:36:39.017-07:00In general, I explore a wide range of K values, th...In general, I explore a wide range of K values, then I select those results most interesting for the discussion (as I wrote above, each particular tree is not significant per se, but it might help illustrating the impact of homoplasy relative to other topologies). In some papers, I used 3-27, in others 5-20: usually, the differences between the two approaches are minimal: in general, the greatest changes in topology are with K values < 6; with K values higher the topologies usually (but not always) converge to the same tree. This happens because with large K values the weight of any extra step in topology is rapidly reduced respect an unweighted setting.<br />So, the mere fact that beyond a certain K all trees are (almost) identical does not necessarily mean that that topology is the "true tree", it is just a consequence that the larger the K value the lowest the impact of homoplasy in producing a tree different from the unweighted setting. Andrea Cauhttps://www.blogger.com/profile/10855060597677361866noreply@blogger.comtag:blogger.com,1999:blog-3248412803814730250.post-20584187456410522242022-03-16T14:07:42.024-07:002022-03-16T14:07:42.024-07:00What's your preferred range of K values then, ...What's your preferred range of K values then, Andrea?Nickhttps://www.blogger.com/profile/08718847558790015112noreply@blogger.comtag:blogger.com,1999:blog-3248412803814730250.post-73888840798856979072022-03-12T06:19:53.403-08:002022-03-12T06:19:53.403-08:00As discussed by Madzia and me (2017: https://peerj...As discussed by Madzia and me (2017: https://peerj.com/articles/3782/), Implied Weighting should be used to test the impact of homoplasy on relationships, and not just to produce more resolved topologies. In any case, trees produced using very aggressive K values (in particular, with K = 5 or less) should place fragmentary OTUs in very bizarre and unlikely placements (e.g., if I re-run my theropod tree with K = 3, Velociraptor osmolskae is usually placed in Ceratosauria).Andrea Cauhttps://www.blogger.com/profile/10855060597677361866noreply@blogger.com