Zamora Samuel, Rahman Imran A, Ausich William I
Instituto Geológico y Minero de España , Zaragoza , Spain.
School of Earth Sciences, University of Bristol , Bristol , United Kingdom.
PeerJ. 2015 Dec 7;3:e1450. doi: 10.7717/peerj.1450. eCollection 2015.
Complete, articulated crinoids from the Ordovician peri-Gondwanan margin are rare. Here, we describe a new species, Iocrinus africanus sp. nov., from the Darriwilian-age Taddrist Formation of Morocco. The anatomy of this species was studied using a combination of traditional palaeontological methods and non-destructive X-ray micro-tomography (micro-CT). This revealed critical features of the column, distal arms, and aboral cup, which were hidden in the surrounding rock and would have been inaccessible without the application of micro-CT. Iocrinus africanus sp. nov. is characterized by the presence of seven to thirteen tertibrachials, three in-line bifurcations per ray, and an anal sac that is predominantly unplated or very lightly plated. Iocrinus is a common genus in North America (Laurentia) and has also been reported from the United Kingdom (Avalonia) and Oman (middle east Gondwana). Together with Merocrinus, it represents one of the few geographically widespread crinoids during the Ordovician and serves to demonstrate that faunal exchanges between Laurentia and Gondwana occurred at this time. This study highlights the advantages of using both conventional and cutting-edge techniques (such as micro-CT) to describe the morphology of new fossil specimens.
来自奥陶纪冈瓦纳大陆边缘的完整、具关节的海百合化石十分罕见。在此，我们描述了一个新物种，非洲艾氏海百合（Iocrinus africanus sp. nov.），它来自摩洛哥达瑞威尔阶的塔德里斯特组。我们结合传统古生物学方法和非破坏性X射线显微断层扫描（显微CT）对该物种的解剖结构进行了研究。这揭示了柱体、远端腕臂和反口杯的关键特征，这些特征隐藏在周围岩石中，若不应用显微CT则无法获取。非洲艾氏海百合的特征包括有七至十三条第三腕，每根腕臂有三个呈直线排列的分支，以及一个主要无板或仅有非常薄的板的肛囊。艾氏海百合属在北美（劳伦大陆）是常见属，在英国（阿瓦隆尼亚）和阿曼（中东冈瓦纳）也有报道。它与分节海百合属一起，代表了奥陶纪时期少数地理分布广泛的海百合类，这表明劳伦大陆和冈瓦纳大陆之间在这个时期发生了动物群交流。这项研究突出了使用传统技术和前沿技术（如显微CT）来描述新化石标本形态的优势。
