Skull anatomy of Dakosaurus andiniensis (Thalattosuchia: Crocodylomorpha) and the phylogenetic position of Thalattosuchia
Skull anatomy of Dakosaurus andiniensis (Thalattosuchia: Crocodylomorpha) and the phylogenetic position of Thalattosuchia
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Dakosaurus andiniensis（海鳄亚目：鳄形目）的头骨解剖和海鳄亚目的系统发育位置
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
Z. Gasparini
中科院分区：
文献类型：
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作者：
D. Pol;Z. Gasparini
本文报道了晚侏罗世和早白垩世达科龙（Dakosaurus andiniensis）的新资料。这里描述的一个标本包括一个几乎完整的头骨和下颚，发现于阿根廷内乌肯省瓦卡穆尔塔组（提托尼亚）的最高层。新的材料允许更完整的理解和诊断这种形式，以前只知道从零碎的模式标本。新的遗骸表明D.安迪尼龙的形态与海洋鳄形动物不一样，即显著短而高的吻部，有锯齿齿。这一新的信息允许测试这个分类群的系统发育关系，它被描绘为深深嵌套在Metriorhynchidae中，Metriorhynchidae是一个海洋鳄形动物的分支，具有对海洋环境的衍生适应性（例如桨状前肢，肥大的鼻盐腺）。特别是D. andiniensis可能是D.欧洲侏罗纪的大菱鲆这种关系重复了其他来自南美洲和欧洲的侏罗纪海洋鳄形类（例如地龙）的系统发育模式，表明这两个遥远的海洋盆地之间有着密切的动物群关系。这里报告的系统发育分析结果在一个最简约的假设，描绘Thalattosuchia巢内Neosuchia和支持这一立场的强度和字符的证据。此外，几个字符传统上假设依赖于长喙形态的严格审查根据新的证据。它们中的大多数显示的字符状态的分布，是不严格兼容的长喙条件，因此，被解释为独立的单位的系统发育证据。
Synopsis New information on Dakosaurus andiniensis from the Latest Jurassic and Early Cretaceous is reported here. One of the specimens described herein consists of an almost complete skull and lower jaw found in the uppermost levels of the Vaca Muerta Formation (Tithonian) of Neuquén Province, Argentina. The new material allows a more complete understanding and diagnosis of this form, previously known only from the fragmentary type specimen. The new remains show that D. andiniensis had an unusual morphology for a marine crocodyliform,namely a remarkably short, high snout with ziphodont dentition. This new information allows testing of the phylogenetic relationships of this taxon, which is depicted as deeply nested within Metriorhynchidae, a clade of marine crocodyliforms with derived adaptations to the marine environment (e.g. paddle‐like forelimbs, hypertrophied nasal salt glands). In particular, D. andiniensis is inferred to be the sister taxon of D. maximus from the Jurassic of Europe. This relationship repeats the phylogenetic pattern seen in other Jurassic marine crocodyliforms from South America and Europe (e.g. Geosaurus), demonstrating the close faunal relationship between these two distant marine basins. The phylogenetic analysis reported here results in a most parsimonious hypothesis that depicts Thalattosuchia nested within Neosuchia and the strength and character evidence supporting this position is presented. In addition, several characters traditionally postulated as dependent upon the longirostrine morphology are critically examined under the light of new evidence. Most of them show a character state distribution that is not strictly compatible with that of the longirostrine condition and, therefore, are interpreted as independent units of phylogenetic evidence.