http://precedings.nature.com/tags/Dinosaur Recently posted documents tagged with 'Dinosaur' Nature Publishing Group en Nature Precedings http://precedings.nature.com/images/header_logo.gif http://precedings.nature.com http://precedings.nature.com/documents/3828/version/1 Limusaurus is a remarkable herbivorous ceratosaur unique among theropods in having digits II, III and IV, with only a small metacarpal vestige of digit I. This raises interesting questions regarding the controversial identity of avian wing digits. The early tetanuran ancestors of birds had tridactyl hands with digital morphologies corresponding to digits I, II & III of other dinosaurs. In bird embryos, however, the pattern of cartilage formation indicates that their digits develop from positions that become digits II, III, & IV in other amniotes. Limusaurus has been argued to provide evidence that the digits of tetanurans, currently considered to be I, II and III, may actually be digits II, III, & IV, thus explaining the embryological position of bird wing digits. However, morphology and gene expression of the anterior bird wing digit specifically resemble digit I, not II, of other amniotes. We argue that digit I loss in Limusaurus is derived and thus irrelevant to understanding the development of the bird wing. http://precedings.nature.com/documents/3828/version/1 Tue, 06 Oct 2009 12:15:57 UTC Limusaurus and bird digit identity hdl:10101/npre.2009.3828.1 2009-10-06 Alexander O. Vargas Nature Precedings 2009-10-06T12:15:57Z Manuscript Developmental Biology Genetics & Genomics Molecular Cell Biology Evolutionary Biology http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/3255/version/1 Molecular analysis of collagen sequences from an 80 million year old hadrosaur B. canadensis and a 68 million year old dinosaur T. rex suggest strongly that B. canadensis is an outgroup to a clade containing T. rex and birds, fully consistent with the well-established phylogeny based on morphological analyses of fossils. http://precedings.nature.com/documents/3255/version/1 Wed, 27 May 2009 14:55:41 UTC Molecular evidence for the hadrosaur B. canadensis as an outgroup to a clade containing the dinosaur T. rex and birds hdl:10101/npre.2009.3255.1 2009-05-27 Shi Huang Nature Precedings 2009-05-27T14:55:41Z Manuscript Bioinformatics Evolutionary Biology http://creativecommons.org/licenses/by/3.0/ http://dx.doi.org/10.1038/npre.2008.2326.1 Recent coelurosaurian discoveries have greatly enriched our knowledge of the dinosaur-bird transition, but all reported taxa close to this transition are from relatively well-known coelurosaurian groups1-3. Here we report a new basal avialan, Epidexipteryx hui gen. et sp. nov., from the Middle-Late Jurassic of Inner Mongolia, China. This new species is characterized by an unexpected combination of characters seen in several different theropod groups, particularly the Oviraptorosauria. Phylogenetic analysis shows it to be the sister taxon to Epidendrosaurus4,5, forming a new clade at the base of Avialae6. Epidexipteryx also possesses two pairs of elongate ribbon-like tail feathers (ETFs), and its limbs lack contour feathers for flight. This finding shows that a member of the avialan lineage experimented with integumentary ornamentation as early as the Middle-Late Jurassic, and provides further evidence relating to this important aspect of the transition from non-avian theropods to birds. http://dx.doi.org/10.1038/npre.2008.2326.1 Wed, 24 Sep 2008 13:34:16 UTC A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers doi:10.1038/npre.2008.2326.1 2008-09-24 Fucheng Zhang Nature Precedings 2008-09-24T13:34:16Z Manuscript Developmental Biology Ecology Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/1676/version/2 There exists a remarkable correlation between genetic distance as measured by protein or DNA dissimilarity and time of species divergence as inferred from fossil records. This observation has provoked the molecular clock hypothesis. However, data inconsistent with the hypothesis have steadily accumulated in recent years from studies of extant organisms. Here the published DNA and protein sequences from ancient fossil specimens were examined to see if they would support the molecular clock hypothesis. The hypothesis predicts that ancient specimens cannot be genetically more distant to an outgroup than extant sister species are. Also, two distinct ancient specimens cannot be genetically more distant than their extant sister species are. The findings here do not conform to these predictions. Neanderthals are more distant to chimpanzees and gorillas than modern humans are. Dinosaurs are more distant to frogs than extant birds are. Mastodons are more distant to opossums than other placental mammals are. The genetic distance between dinosaurs and mastodons is greater than that between extant birds and mammals. Therefore, while the molecular clock hypothesis is consistent with some data from extant organisms, it has yet to find support from ancient fossils. Far more damaging to the hypothesis than data from extant organisms, which merely question the constancy of mutation rate, the study of ancient fossil organisms here challenges for the first time the fundamental premise of modern evolution theory that genetic distances had always increased with time in the past history of life on Earth. http://precedings.nature.com/documents/1676/version/2 Fri, 25 Jul 2008 15:02:55 UTC Ancient fossil specimens of extinct species are genetically more distant to an outgroup than extant sister species are hdl:10101/npre.2008.1676.2 2008-07-25 Shi Huang Nature Precedings 2008-07-25T15:02:55Z Manuscript Bioinformatics Evolutionary Biology http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/1676/version/1 There exists a remarkable correlation between genetic distance and time of species divergence as inferred from fossil records. This observation has provoked the molecular clock hypothesis. However, data inconsistent with the hypothesis have steadily accumulated in recent years from studies on extant organisms. Here the published DNA and protein sequences from ancient fossil specimens were examined to see if they would support the molecular clock hypothesis. The hypothesis predicts that ancient specimens cannot be genetically more distant to an outgroup than extant sister species are. Also, two distinct ancient specimens cannot be genetically more distant than their extant sister species are. The findings here did not support these predictions. Neanderthals are more distant to chimpanzees and gorillas than modern humans are. Dinosaurs are more distant to frogs than extant birds are. Mastodons are more distant to opossums than other placental mammals are. The genetic distance between dinosaurs and mastodons is greater than that between extant birds and mammals. Therefore, while the molecular clock hypothesis is consistent with some data from extant organisms, it has yet to find support from ancient fossils. http://precedings.nature.com/documents/1676/version/1 Wed, 12 Mar 2008 21:06:37 UTC Ancient fossil specimens of extinct species are genetically more distant to an outgroup than extant sister species are hdl:10101/npre.2008.1676.1 2008-03-12 Shi Huang Nature Precedings 2008-03-12T21:06:37Z Manuscript Ecology http://creativecommons.org/licenses/by/3.0/ http://dx.doi.org/10.1038/npre.2007.508.1 Though titanosaur osteoderms are not common findings, these elements are recorded widely in Gondwana and part of Laurasia. This assembly known by the date offers few resources for studies on the ecology of this group of dinosaurs. Recently, some eggs bearing titanosaur embryos with preserved skin, from Patagonia, Argentina, may shed some light on the function and disposition pattern of these dermic bones. Some of the skin patches associated with the titanosaur embryos show two distinct patterns of tuberosities: a longitudinal row and rosettes, both composed of closely attached tuberosities. These tuberosities do not seem to be ossified, but this might be due to the ontogenetic stage of the titanosaurs. Here we propose that these tuberosities might have been ossified in later ontogenetic stages, and then turning into real osteoderms providing physical defence for the juvenile titanosaurs. Amongst the remains of large titanosaurs like Mendozasaurus neguyelap some osteoderms were recovered, but it is contrasting small to the animal when compared to other dinosaurs. These bones would not provide real defensive advantage to an adult titanosaur as they are small and also have a very spongy internal structure. This apparent fragility also may be the reason that few titanosaur osteoderms have been preserved. In comparison, the tuberosity of a young titanosaur is much larger than an adult osteoderm and its body armor would be much more effective against small predators like notosuchian crocodyliforms and small theropods. And if the titanosaur osteoderms are originated from the embryo’s tuberosities, the disposition of these elements in an adult animal would be very distant to each other. The calcium reserve may be considered as functional for an adult titanosaur though. http://dx.doi.org/10.1038/npre.2007.508.1 Thu, 26 Jul 2007 05:20:44 UTC Functional aspects of titanosaur osteoderms doi:10.1038/npre.2007.508.1 2009-03-04 Thiago S. Marinho Nature Precedings 2007-07-26T05:20:44Z Poster Ecology http://creativecommons.org/licenses/by/2.5/