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Quantifying shell outline variability in extant and fossil Laqueus (Brachiopoda: Terebratulida): are outlines good proxies for long-looped brachidial morphology and can they help us characterize species?
Paleobiology ( IF 2.7 ) Pub Date : 2020-12-29 , DOI: 10.1017/pab.2020.56
Natalia López Carranza , Sandra J. Carlson

Extant and extinct terebratulide brachiopod species have been defined primarily on the basis of morphology. What is the fidelity of morphological species to biological species? And how can we test this fidelity with fossils? Taxonomically and phylogenetically, the most informative internal feature in the brachiopod suborder Terebratellidina is the geometrically complex long-looped brachidium, which is highly fragile and only rarely preserved in the fossil record. Given this, it is essential to test other sources of morphological data, such as valve outline shape, when trying to recognize and identify species. We analyzed valve outlines and brachidia in the genus Laqueus to explore the utility of shell shape in discriminating extant and fossil species. Using geometric morphometric methods, we quantified valve outline variability using elliptical Fourier methods and tested whether long-looped brachidial morphology correlates with shell outline shape. We then built classification models based on machine learning algorithms using outlines as shape variables to predict fossil species’ identities. Our results demonstrate that valve outline shape is significantly correlated with long-looped brachidial shape and that even relatively simple outlines are sufficiently morphologically distinct to enable extant Laqueus species to be identified, validating current taxonomic assignments. These are encouraging results for the study and delimitation of fossil terebratulide species, and their recognition as biological species. In addition, machine learning algorithms can be successfully applied to help solve species recognition and delimitation problems in paleontology, especially when morphology can be characterized quantitatively and analyzed statistically.

中文翻译:

量化现存和化石 Laqueus (Brachiopoda: Terebratulida) 的贝壳轮廓变异性:轮廓是长环状肱动物形态的良好代理,它们可以帮助我们表征物种吗?

现存和灭绝的 terebratulide 腕足类物种主要是根据形态来定义的。形态物种对生物物种的保真度是多少?我们如何用化石测试这种保真度?在分类学和系统发育学上,腕足亚目 Terebratellidina 中信息最丰富的内部特征是几何复杂的长环状臂,它非常脆弱,很少保存在化石记录中。鉴于此,在尝试识别和识别物种时,必须测试其他形态数据来源,例如瓣膜轮廓形状。我们分析了该属的瓣膜轮廓和肱骨拉奎斯探索贝壳形状在区分现存和化石物种中的效用。使用几何形态测量方法,我们使用椭圆傅里叶方法量化瓣膜轮廓变异性,并测试长环肱形态是否与壳轮廓形状相关。然后,我们基于机器学习算法构建分类模型,使用轮廓作为形状变量来预测化石物种的身份。我们的研究结果表明,瓣膜轮廓形状与长环状肱动脉形状显着相关,即使是相对简单的轮廓在形态上也足够明显,以使现存的拉奎斯要识别的物种,验证当前的分类学分配。这些对于研究和划定化石 terebratulide 物种以及将它们识别为生物物种是令人鼓舞的结果。此外,机器学习算法可以成功地应用于帮助解决古生物学中的物种识别和划界问题,特别是当形态可以定量表征和统计分析时。
更新日期:2020-12-29
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