The Giant Cretaceous Coelacanth (Actinistia, Sarcopterygii) Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and Its Bearing on Latimerioidei Interrelationships
The Giant Cretaceous Coelacanth (Actinistia, Sarcopterygii) Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and Its Bearing on Latimerioidei Interrelationships
复制标题
DOI：
10.1371/journal.pone.0049911
复制
发表时间：
2012-11-27
期刊：
影响因子：
3.7
通讯作者：
Clement, Gael
中科院分区：
文献类型：
--
作者：
Dutel, Hugo;Maisey, John G.;Clement, Gael
本文对产于北美晚白垩世的巨型腔棘鱼Megalocoelacanthus dobiei进行了重新描述。巨腔棘鱼以前曾在由孤立元素组成的复合材料的基础上进行过描述。因此，它的解剖学的许多方面仍然未知，以及它与其他腔棘鱼的系统发育关系。以前的研究表明，Megalocoelacanthus更接近Latimeria和Macropoma而不是Mawsonia。然而，这一假设仅基于少数解剖特征的总体相似性，而不是基于系统发育特征分析。在堪萨斯的Niobrara组中发现了一个新的、保存完好的标本，可以详细描述Megalocoelacanthus的头骨，并阐明它与其他腔棘鱼的系统发育关系。虽然非常扁平，但头骨和颌骨保存完好，并显示出许多与Latimeriidae共享的衍生特征，如Latimeria，Macropoma和Libys。值得注意的是，顶鼻盾是狭窄的，两侧是非常大的，连续的空泡形成眶上感觉线管。这种不寻常的形态在Libys中也是已知的。巨腔棘鱼的一些其他特征，如其巨大的体型和没有牙齿，与Mawsoniid属Mawsonia和Axelrophilthys共有。我们的分支分析支持姐妹组的关系Megalocoelacanthus和Libys在Latimeriidae。这种拓扑结构表明，无齿，大尺寸的腔棘鱼在Latimeriidae和Mawsoniidae在中生代独立进化。基于以前的拓扑结构和我们的，我们然后审查的高层次分类Latimerioidei，并提出新的系统发育的定义。
We present a redescription of Megalocoelacanthus dobiei, a giant fossil coelacanth from Upper Cretaceous strata of North America. Megalocoelacanthus has been previously described on the basis of composite material that consisted of isolated elements. Consequently, many aspects of its anatomy have remained unknown as well as its phylogenetic relationships with other coelacanths. Previous studies have suggested that Megalocoelacanthus is closer to Latimeria and Macropoma than to Mawsonia. However, this assumption was based only on the overall similarity of few anatomical features, rather than on a phylogenetic character analysis. A new, and outstandingly preserved specimen from the Niobrara Formation in Kansas allows the detailed description of the skull of Megalocoelacanthus and elucidation of its phylogenetic relationships with other coelacanths. Although strongly flattened, the skull and jaws are well preserved and show many derived features that are shared with Latimeriidae such as Latimeria, Macropoma and Libys. Notably, the parietonasal shield is narrow and flanked by very large, continuous vacuities forming the supraorbital sensory line canal. Such an unusual morphology is also known in Libys. Some other features of Megalocoelacanthus, such as its large size and the absence of teeth are shared with the mawsoniid genera Mawsonia and Axelrodichthys. Our cladistic analysis supports the sister-group relationship of Megalocoelacanthus and Libys within Latimeriidae. This topology suggests that toothless, large-sized coelacanths evolved independently in both Latimeriidae and Mawsoniidae during the Mesozoic. Based on previous topologies and on ours, we then review the high-level taxonomy of Latimerioidei and propose new systematic phylogenetic definitions.