Cardichelyon rogerwoodi is an enigmatic fossil turtle from the late Paleocene to early Eocene of North America. Previous analyses suggested affiliation with Testudinoidea, in particular the big-headed turtle Platysternon megacephalum, based on the presence of multiple musk-duct foramina and a large head. We here highlight previously undocumented characteristics for this turtle, notably the presence of short costiform processes, a rib-like axillary process, and a posterior plastral hinge. Phylogenetic analysis places Cardichelyon rogerwoodi within Testudinoidea, but the exclusion of testudinoids suggest an affiliation with Dermatemydidae. Using consilience with external data we favor placement within Kinosternoidea. Cardichelyon rogerwoodi is therefore an aberrant, hinged kinosternoid that developed in situ in North America during the Paleocene long before the arrival of testudinoids on this continent in the early Eocene.

中文翻译：

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古近纪海龟 Cardichelyon rogerwoodi 的另一种解释是铰链式类固醇

Cardichelyon 罗杰伍德是北美洲古新世晚期至始新世早期的神秘龟化石。先前的分析表明与 Testudinoidea 有联系，特别是大头龟大头扁骨，基于多个麝香管孔和一个大头的存在。我们在这里强调了这只乌龟以前没有记录的特征，特别是短肋状突、肋状腋突和后胸骨铰链的存在。系统发育分析场所Cardichelyon 罗杰伍德在 Testudinoidea 内，但排除 testudinoids 表明与 Dermatemydidae 有联系。使用与外部数据的一致性，我们倾向于将其放置在 Kinosternoidea 中。Cardichelyon 罗杰伍德因此，它是一种异常的铰接类kinosternoid，早在始新世早期testudinoids到达该大陆之前很久就在古新世期间在北美原位发育。