A New Sebecid from the Paleogene of Brazil and the Crocodyliform Radiation after the K–Pg Boundary
A New Sebecid from the Paleogene of Brazil and the Crocodyliform Radiation after the K–Pg Boundary
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巴西古近纪的新 Sebecid 和 K-Pg 边界后的鳄鱼辐射
作者：
A. Kellner;A. E. Pinheiro;D. Campos
一种新的鳄鱼形，sahitissuchus fluuminensis gen. et sp. nov.，基于在巴西巴西里约热内卢的s<s:1> o jos<s:1> de Itaboraí盆地收集的一个完整的头骨、下颌和前颈椎进行了描述。该标本是迄今为止在古新世沉积物中保存最完好的鳄鱼类之一，代表了sebecosuchian，这是少数几个在白垩纪-古近纪生物危机中幸存下来的分支之一。这个新分类群与一个鳄鱼类在同一沉积物中被发现，鳄鱼类在古近纪经历了巨大的多样化。sebecosuchian的记录表明，在白垩纪-古近纪的生物危机之后，与bauusuchid sebecosuchian相比，这个分支中不太专业的成员（以牙齿数量较多为特征）存活了下来，一些人有陆地生活习惯，而另一些人则发展成半水生生活方式（例如Lorosuchus）。从始新世开始，sebecid sebecosuchians在Sebecus和Langstonia中观察到，变得更加专业化，但没有显示出白垩纪baurusuchid sebecosuchians发展的典型的减少牙齿。Barinasuchus arveloi是一种中新世高吻鳄鱼类，其基底位置表明，在K-Pg生物危机后出现了一个独立的分支，并发展出了突出的生态系统，表明K-Pg后鳄鱼形辐射的历史更为复杂。
A new crocodyliform, Sahitisuchus fluminensis gen. et sp. nov., is described based on a complete skull, lower jaw and anterior cervical vertebrae collected in the São José de Itaboraí Basin of Rio de Janeiro, Brazil. The specimen is one of the best preserved crocodyliforms from Paleocene deposits recovered so far and represents a sebecosuchian, one of the few clades that survived the Cretaceous-Paleogene biotic crisis. The new taxon is found in the same deposit as an alligatoroid, a group that experienced large diversification in the Paleogene. The sebecosuchian record suggests that after the Cretaceous-Paleogene biotic crisis, the less specialized members of this clade characterized by a higher number of teeth compared to the baurusuchid sebecosuchians survived, some having terrestrial habits while others developed a semi-aquatic life style (e.g., Lorosuchus). Starting in the Eocene, sebecid sebecosuchians became specialized with a more accentuated oreinirostry as observed in Sebecus and in Langstonia, but not showing the typical reduced dentition developed by the Cretaceous baurusuchid sebecosuchians. The basal position of Barinasuchus arveloi, a high-snouted Miocene sebecid, indicates the occurrence of an independent lineage sometime after the K-Pg biotic crisis that developed accentuated oreinirostry, suggesting a more complex history of the post-K-Pg crocodyliform radiation.