泥潭龙发育过程中的变化



楼主 RAX博士  发布于 2016-12-25 23:42:00 +0800 CST  
Extreme Ontogenetic Changes in a Ceratosaurian Theropod


Ontogenetic variation is documented within many dinosaur species, but extreme ontogenetic changes are rare among dinosaurs, particularly among thero- pods. Here,we analyze19 specimensofthe Jurassic ceratosaurian theropod Limusaurus inextricabilis, representing six ontogenetic stages based on body size and histological data. Among 78 ontogenetic changes we identify in these specimens, the most unexpected one is the change from fully toothed jaws in the hatchling and juvenile individuals to a completely toothless beaked jaw in the more mature individuals, representing the first fossil record of ontogenetic edentulism among the jawed verte- brates. Jaw morphological data, including those derived from Mi-CT and SR-mCT scanning of Limu- saurus specimens, reveal dental alveolar vestiges and indicate that ontogenetic tooth loss in Limusau- rus is a gradual, complex process. Our discovery has significant implications for understanding the evolution of the beak, an important feeding structure present in severaltetrapodclades,including modern birds. This radical morphological change suggests a dietary shift, probably from omnivory for juvenile Limusaurus to herbivory for adult Limusaurus, which is also supported by additional evidence from gastroliths and stable isotopes. Incorporating new ontogenetic information from Limusaurus into phylogenetic analyses demonstrates surprisingly lit- tle effect on its placement when data from different stages are used exclusively, in contrast to previous analyses of tyrannosaurids, but produces subtle differences extending beyond the placement of Limusaurus.

楼主 RAX博士  发布于 2016-12-25 23:43:00 +0800 CST  
许多恐龙在成长的过程中都会发生一些变化,但是发生极端变化的还是很少数。在最近对19具不同年龄段的泥潭龙标本的研究中,发现它们在发育的过程中会有显著的变化,其中最突出的就是其牙齿的变化。逐渐成长的过程中,泥潭龙的头部形态会有所改变,牙齿也会逐渐的脱落,演变成类似喙的结构。这种变化意味着泥潭龙可能在成长阶段中食性的改变,由杂食变成植食。

楼主 RAX博士  发布于 2016-12-25 23:50:00 +0800 CST  





楼主 RAX博士  发布于 2016-12-25 23:52:00 +0800 CST  

楼主:RAX博士

字数:1832

发表时间:2016-12-26 07:42:00 +0800 CST

更新时间:2017-04-01 09:27:49 +0800 CST

评论数:16条评论

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