Shell asymmetry in Cretaceous Cyclothyrididae (Brachiopoda): variability, ontogeny and terminology

IF 1.2 4区 地球科学 Q3 PALEONTOLOGY
Danièle Gaspard, Denis Paccard, Jérémie Bardin
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引用次数: 0

Abstract

The asymmetry observed in rhynchonellid brachiopod shells has been discussed for decades and continues to attract attention. This noteworthy modification of the anterior margin morphology during the ontogeny has evolved several times in rhynchonellids, and seems to reflect a genetic basis. First, we try to clarify the terminology regarding asymmetrical, dissymmetrical and symmetrical shells that has existed since the beginning of the 20th century. The Cretaceous populations observed clearly exhibit antisymmetry (also called random asymmetry). During the Cretaceous, some populations of Cyclothyris McKoy, 1844 include a mixture of truly asymmetrical specimens and others that exhibit an intermediate degree of asymmetry, herein called atypical morphologies. Shapes of specimens coming from two different locations in France were captured using geometric morphometrics. We used the range of different morphologies: 1) to test alternative hypotheses about the ontogeny of asymmetry; 2) to test for the possibility of several morphogroups; and 3) to discuss the determinism of the asymmetry.
白垩纪旋毛虫科(腕足动物)的壳不对称:变异性、本体和术语
几十年来,人们一直在讨论纹孔腕足动物贝壳中观察到的不对称现象,这种现象也一直吸引着人们的注意。这种值得注意的前缘形态学变化在脊索动物中经历了多次进化,似乎反映了一种遗传基础。首先,我们试图澄清自 20 世纪初以来一直存在的关于不对称、不对称和对称贝壳的术语。所观察到的白垩纪种群明显表现出不对称(也称随机不对称)。在白垩纪,麦考伊(Cyclothyris McKoy,1844 年)的一些种群包括真正不对称的标本和其他表现出中等程度不对称的标本(此处称为非典型形态)。我们使用几何形态计量学捕捉了来自法国两个不同地点的标本的形状。我们利用不同形态的范围1) 检验关于不对称本体的其他假设;2) 检验几种形态群的可能性;3) 讨论不对称的决定性。
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来源期刊
Comptes Rendus Palevol
Comptes Rendus Palevol 地学-古生物学
CiteScore
2.10
自引率
0.00%
发文量
39
审稿时长
17.6 weeks
期刊介绍: Comptes Rendus Palevol is a fully electronic and peer-reviewed journal, with a continuous publication stream, devoted to palaeontology, prehistory and evolutionary sciences. It publishes original research results, in French or English, in the following domains: systematic and human palaeontology, prehistory, evolutionary biology and macroevolution, and history of sciences. Thematic issues may also be published under the responsibility of a guest editor. All articles published in Comptes Rendus Palevol are compliant with the different nomenclatural codes. A copyright assignment will be signed by the authors before publication.
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