A new megalosaurid theropod dinosaur from the late Middle Jurassic (Callovian) of north-western Germany: Implications for theropod evolution and faunal turnover in the Jurassic
A new megalosaurid theropod dinosaur from the late Middle Jurassic (Callovian) of north-western Germany: Implications for theropod evolution and faunal turnover in the Jurassic
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DOI：
10.26879/654
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发表时间：
2016
影响因子：
2
通讯作者：
O. Rauhut;T. Hübner;K. Lanser
中科院分区：
文献类型：
--
作者：
O. Rauhut;T. Hübner;K. Lanser
在德国北威斯特伐利亚州东北部的海洋中，发现了一只体型庞大、结实的兽脚亚目恐龙的残片。标本包括上颌骨前、上颌骨、泪骨、眶后、牙状、几个尾椎骨、肋骨、腓骨、黄体和部分跟骨。本文将其描述为一种新的巨骨类，名为Wiehenvenator albati n. gen. n. sp.，其诊断依据为上颌骨上升突底部的上颌眶前窝强烈缩小，泪孔前腹侧有一个额外的气压凹陷，眶后侧有一个横向扩张的眶突，以及黄体上升突近端侧屈。系统发育分析恢复Wiehenvenator为巨龙属巨龙，是晚侏罗世龙龙属的姐妹分类群。因此，它增加了中侏罗世巨龙类的相当大的多样性。经时间校准的兽脚亚目的系统发育表明，在托瓦西亚和Bathonian之间，兽脚亚目的快速辐射。这种辐射可能是由Pliensbachian-Toarcian灭绝事件引发的，这可能比三叠纪-侏罗纪灭绝对兽脚亚目恐龙的进化更重要。化石记录表明，中侏罗世以巨龙类为主的动物群向晚侏罗世以异特龙/虚骨龙为主的动物群转变。然而，中晚侏罗世兽脚亚目化石记录在地理位置分布以及采样环境方面的差异，使得这种推断存在问题，至少在异蜥脚类方面是如此。对异特龙类和巨龙类的环境偏好分析表明，异特龙类偏好内陆环境，而巨龙类更常见于近岸环境。
Fragmentary remains of a large, robustly built theropod dinosaur were recovered from the marine middle Callovian Ornatenton Formation of north-eastern Northrhine-Westphalia, Germany. The specimen includes a premaxilla, maxilla, lacrimal, postorbital, dentary, several caudal vertebrae, ribs, fibulae, astragalus, and partial calcaneum. It is here described as a new species of megalosauroid, Wiehenvenator albati n. gen. n. sp., diagnosed by a strongly reduced maxillary antorbital fossa on the base of the ascending process of the maxilla, a very short anterior ramus of the lacrimal with an additional pneumatic depression anteroventral to the lacrimal fenestra, a transversely expanded orbital facet in the postorbital, and a laterally flexed proximal end of the ascending process of the astragalus. Phylogenetic analysis recovers Wiehenvenator as a megalosaurine megalosaurid, sister taxon to the Late Jurassic genus Torvosaurus. It thus adds to the considerable diversity of megalosauroids in the Middle Jurassic. A time-calibrated phylogeny of theropods indicates a rapid radiation of averostran theropods between the Toarcian and the Bathonian. This radiation was probably triggered by the Pliensbachian-Toarcian extinction event, which might have been more important for theropod evolution than the Triassic-Jurassic extinction. The fossil record indicates a faunal turnover from megalosauroid dominated Middle Jurassic to allosauroid / coelurosaur dominated Late Jurassic faunas. However, differences in the Middle and Late Jurassic theropod fossil records both in respect to geographic distribution of localities, as well as sampled environments make this inference problematic, at least in respect to allosauroids. An analysis of environmental preferences of allosauroids and megalosauroids indicates that the former preferred inland environments, whereas the latter are more common in nearshore environments.