Evaluating the origin of Cynodontia (Synapsida, Therapsida) using 3D-Imaging Technologies

使用 3D 成像技术评估犬齿兽亚纲（Synapsida、Therapsida）的起源

• 批准号: 426794378
• 负责人: Professor Dr. Jörg Fröbisch, Ph.D.
• 金额: --
• 依托单位: Paleontological Institute
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/426794378?language=en
• 关键词: Evaluating; origin; Cynodontia; Synapsida; Therapsida

Cynodontia is the most abundant and diverse group of synapsids, as it includes mammals, which evolved from non-mammalian cynodonts in the Late Triassic. The evolution of mammals from cynodonts is one of the best-understood and well-studied major transitions in the fossil record. In contrast, the origin of cynodonts themselves from other synapsids is very poorly known. It is well-established that cynodonts are most closely related to Therocephalia, but it is not clear whether cynodonts and therocephalians are sister-taxa or whether therocephalians are paraphyletic with regards to cynodonts. Also uncertainties exist concerning the phylogenetic relationships of the earliest member of this clade. By contrast, the relationships of higher cynodonts (eucynodonts) are well understood. The main objectives of the proposed project are a re-evaluation of the relationships of Eutheriodontia (Cynodontia+Therocephalia) and an assessment of character evolution within the group based on new CT data, i.e. detailed descriptions of the endocranial anatomy of the earliest known (late Permian and Early Triassic) cynodonts and selected therocephalian relatives. Modern 3D-imaging technologies using computed tomography can make previously-unseen endocranial data readily available, which are a largely untapped resource for understanding therapsid evolution, despite their greater stability and phylogenetic utility than many functionally-variable external craniodental characters. The primary hypothesis to be tested using these data is whether Cynodontia and Therocephalia are sister-taxa or whether cynodonts evolved from within Therocephalia. Furthermore, the novel insights into the endocranial anatomy are useful to test if the origin of characteristic mammalian but also cynodont characters can be traced back deeper in eutheriodont phylogeny and allow, at the same time, to investigate the deep-time evolution of delicate endocranial structures, such as the epipterygoid or alisphenoid elements. Finally, in addition to testing questions of cynodont origins, the new data will also help to resolve the currently unstable intra- and interrelationships among early cynodonts and therocephalians using modern phylogenetic approaches.

Cynodontia是最丰富和多样的联会动物群，因为它包括哺乳动物，在晚三叠世从非哺乳动物的Cynodonts进化而来。哺乳动物从犬齿兽的进化是化石记录中最好理解和研究的主要转变之一。相比之下，犬齿兽本身从其他联会动物的起源知之甚少。犬齿兽与兽头兽的亲缘关系最为密切，但尚不清楚犬齿兽与兽头兽是否为姊妹类群，或者兽头兽是否与犬齿兽并系。也存在不确定性的系统发育关系最早的成员，这支。相比之下，高等犬齿动物（Eucynodonts）的关系已经很好理解。拟议项目的主要目标是重新评估Eutheriodontia（Cynodontia+Therocephalia）的关系，并根据新的CT数据评估该组内的特征演化，即详细描述已知最早（二叠纪末和三叠纪初）的犬齿兽和选定的Therocephalian亲属的颅内解剖。现代3D成像技术，使用计算机断层扫描可以使以前看不见的endocranial数据容易获得，这是一个很大程度上未开发的资源，了解therapsid进化，尽管他们更大的稳定性和系统发育的效用比许多功能可变的外部cranodental字符。使用这些数据进行测试的主要假设是Cynodontia和Therocephalia是否是姐妹类群，或者Cynodonts是否从Therocephalia内部进化而来。此外，对颅内解剖学的新见解有助于测试特征性哺乳动物的起源，但也犬齿特征可以追溯到更深的真兽齿类的发生，并允许，在同一时间，调查微妙的颅内结构，如翼上突或alisphenoid元素的深时间演化。最后，除了测试犬齿动物起源的问题外，新数据还将有助于使用现代系统发育方法解决早期犬齿动物和兽头类动物之间目前不稳定的内部和相互关系。