tag:blogger.com,1999:blog-5519292617097628087.post4182976965113242688..comments2024-01-02T16:09:12.886-07:00Comments on Chinleana: Comparing the Tooth Enamel Microstructure of the Pseudosuchian Revueltosaurus and the Proposed Triassic Ornithischian KrzyzanowskisaurusBill Parkerhttp://www.blogger.com/profile/05941940882532354219noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-5519292617097628087.post-85145191876610985132013-01-13T16:27:07.269-07:002013-01-13T16:27:07.269-07:00This enamel microstructure data is very cool and i...This enamel microstructure data is very cool and informative. It would be interesting to know what patterns might be found with other Triassic teeth such as <i>Tecosaurus</i>, <i>Pretecovasaurus</i>, <i>Crosbysaurus</i>, etc.<br /><br />The comments by Heckert & Miller-Camp on the Blue Hills material and whether or not <i>Krzyzanowskisaurus hunti</i> should be referred to <i>Revueltosaurus</i> are dissappointing, because they unfortunately do not accurately summarize what we said in Irmis et al. 2007 (<i>Historical Biology</i>). We actually *never* officially referred the osteoderms and squamosal to <i>R. hunti</i>, all we said is that they're diagnostic of the genus <i>Revueltosaurus</i>, and this would be *consistent* with <i>R. hunti</i> being assignable to <i>Revueltosaurus</i>. Here's the full passage:<br /><br />"We tentatively retain <i>R. hunti</i> in <i>Revueltosaurus</i> (as a probable pseudosuchian) based on the characters it shares with <i>R. callenderi</i> that Heckert (2002) outlined and that the teeth were found at the Blue Hills locality in Arizona (UCMP loc. 7308) in association with a squamosal (UCMP 165205), quadrate (UCMP 165206), and osteoderms that are identical to those of <i>R. callenderi</i>. These osteoderms were described by Heckert and Lucas (2002) as juvenile specimens of the aetosaur <i>Stagonolepis wellesi</i>, but they are indistinguishable from the osteoderms described by Parker et al. (2005) for <i>R. callenderi</i>. This evidence, combined with the fact that <i>R. hunti</i> lacks a true asymmetric basal swelling, prevents these teeth from being unambiguously assigned to the Ornithischia."<br /><br />Yes, the lack of unambiguous association and overlapping elements within the Blue Hills specimens makes it difficult to say the dental material belongs to the same taxon as the non-dental skeletal material. But, as Bill points out, each individual element can be referred to <i>Revueltosaurus</i> based on unambiguous apomorphies, and this includes the teeth of <i>R. hunti</i>. The important point is that this is *consistent* with the hypothesis that the cranial and osteoderm material belongs to the <i>R. hunti</i> material. An alternative hypothesis would be that there are two or more species of <i>Revueltosaurus</i> in the Blue Hills assemblage, but this seems less parsimonious without any evidence of multiple taxa (e.g., seeing two morphotypes of the same element).220myahttps://www.blogger.com/profile/06403919493457640549noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-84584624537543541392013-01-12T13:04:29.495-07:002013-01-12T13:04:29.495-07:00Again that would suggest the presence of more than...Again that would suggest the presence of more than one Revueltosaurus-like animal. The teeth of R. hunti possess characters that are shared with R. callenderi exclusive of other taxa. This is why Heckert referred them to Revueltosaurus in 2002. After it was determined that R. callenderi was not a dinosaur, R. hunti was assigned to a new genus in hopes that it still would prove to be dinosaurian. However, the current evidence is against this (i.e. presence of Revueltosaurus bones in same quarry, tooth microstructure). The lack of overlap is always a problem but we can use autapomorphies to make referrals. Bill Parkerhttps://www.blogger.com/profile/05941940882532354219noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-51580222367266882902013-01-12T12:19:33.549-07:002013-01-12T12:19:33.549-07:00It's true that the squamosal and armor found a...It's true that the squamosal and armor found at St Johns quarry was found associated with teeth of Krzyzanowskisaurus. But the lack of overlap with the teeth is an obstacle to referring the osteoderms to K. hunti. Davidowhttps://www.blogger.com/profile/06099864739987549261noreply@blogger.comtag:blogger.com,1999:blog-5519292617097628087.post-8521854044198716162013-01-12T12:06:28.174-07:002013-01-12T12:06:28.174-07:00Can't wait til Tschopp et al. becomes availabl...Can't wait til Tschopp et al. becomes available. Potentially a lot more interesting.<br /><br />I'm not sure if I'd be very convinced by enamel microstructure characters alone either, there's a thesis out there where the author was unable to find phylogenetic signal in a set of them for even closely related crocodilians, IIRC. I'm sure there are plenty of cases where they are relevant, but they are probably subject to the same variation that everything else is.Anonymousnoreply@blogger.com