Diversity Patterns of nonmammalian cynodonts (Synapsida, Therapsida) and the impact of taxonomic practice and research history on diversity estimates
Diversity Patterns of nonmammalian cynodonts (Synapsida, Therapsida) and the impact of taxonomic practice and research history on diversity estimates
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DOI：
10.1017/pab.2018.38
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发表时间：
2018-12
期刊：
影响因子：
2.7
通讯作者：
Marcus Lukic-Walther;N. Brocklehurst;C. Kammerer;J. Fröbisch
中科院分区：
文献类型：
--
作者：
Marcus Lukic-Walther;N. Brocklehurst;C. Kammerer;J. Fröbisch
抽象的。非哺乳类的犬齿兽是一个物种丰富、生态多样的类群，化石记录从二叠纪晚期一直延续到白垩纪。由于它们是三叠纪陆地生态系统的主要组成部分，也是哺乳动物的直接祖先，犬齿兽是了解中生代四足动物多样性的重要群体。我们研究模式的非哺乳动物犬齿物种丰富度和质量的化石记录。最近发表的树木和时间校准使用贝叶斯方法构建的超树犬齿。虽然这种方法将Cynodontia的根推回到最早的瓜达卢普世，但Cynognathia和Probainognathia的起源接近于它们在化石记录中的首次出现。分类，二次抽样，和系统发育多样性的估计支持一个主要的犬齿辐射结束二叠纪大规模灭绝后，但在三叠纪末观察到相互矛盾的信号。分类多样性的估计显示高的多样性在雷蒂安和下降跨越三叠纪/侏罗纪边界，而系统发育多样性表明更早的灭绝之间的Norian和雷蒂安。这种差异是由于流行的分类群的基础上，牙齿在雷蒂亚，这是不包括在系统发育多样性估计。通过地质时间检查犬齿标本的完整性并不支持保存潜力的下降;虽然中位完整性评分在晚三叠世下降，但值的范围保持一致。相反，较差的完整性分数归因于采样和分类实践的转变：微脊椎动物采样和碎片材料命名的流行率增加。
Abstract. Nonmammalian cynodonts represent a speciose and ecologically diverse group with a fossil record stretching from the late Permian until the Cretaceous. Because of their role as major components of Triassic terrestrial ecosystems and as the direct ancestors of mammals, cynodonts are an important group for understanding Mesozoic tetrapod diversity. We examine patterns of nonmammalian cynodont species richness and the quality of their fossil record. A supertree of cynodonts is constructed from recently published trees and time calibrated using a Bayesian approach. While this approach pushes the root of Cynodontia back to the earliest Guadalupian, the origins of Cynognathia and Probainognathia are close to their first appearance in the fossil record. Taxic, subsampled, and phylogenetic diversity estimates support a major cynodont radiation following the end-Permian mass extinction, but conflicting signals are observed at the end of the Triassic. The taxic diversity estimate shows high diversity in the Rhaetian and a drop across the Triassic/Jurassic boundary, while the phylogenetic diversity indicates an earlier extinction between the Norian and Rhaetian. The difference is attributed to the prevalence of taxa based solely on teeth in the Rhaetian, which are not included in the phylogenetic diversity estimate. Examining the completeness of cynodont specimens through geological time does not support a decrease in preservation potential; although the median completeness score decreases in the Late Triassic, the range of values remains consistent. Instead, the poor completeness scores are attributed to a shift in sampling and taxonomic practices: an increased prevalence in microvertebrate sampling and the naming of fragmentary material.