论文标题：Old African fossils provide new evidence for the origin of the American crocodiles

期刊：Scientific Reports

作者：Massimo Delfino and Dawid A. Iurino et al.

发表时间：2020/07/23

DOI：10.1038/s41598-020-68482-5

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根据《科学报告》发表的一项研究Old African fossils provide new evidence for the origin of the American crocodiles，已灭绝的一种非洲鳄鱼——切奇亚鳄（Crocodylus checchiai）可能与现存的美洲鳄鱼关系密切。这项发现表明鳄鱼可能在晚中新世（1100万-500万年前）从非洲迁移到美洲。

在此之前，研究人员并不清楚鳄鱼是从非洲迁移到美洲还是相反——假设通过一次跨大西洋航行。意大利都灵大学的Massimo Delfino和意大利罗马大学的Dawid Iurino等人使用CT重新检查了一块1939年在利比亚As Sahabi发现、现存于罗马大学地球科学博物馆的切奇亚鳄头骨，鉴定出了若干新的头骨结构，包括吻部中央的一个突起，这种结构从未在任何其他非洲鳄鱼物种身上发现过，但是可见于四种现存的美洲鳄鱼：奥利诺科鳄（Crocodylus intermedius），莫瑞雷鳄（C. moreleti），美洲鳄（C. acutus）和古巴鳄（C. rhombifer）。这个共同的头骨结构表明切奇亚鳄和美洲鳄鱼之间具有密切的演化关系。

Crocodylus checchiai外形的艺术复原图 | 作者：Dawid A. lurino

进一步的种间演化关系分析显示，切奇亚鳄可能和在现今南北美洲发现的四个鳄鱼物种属于同一谱系。切奇亚鳄的遗骸可以追溯到700万年前左右，而已灭绝的美洲鳄鱼法尔康鳄（C. falconensis）的遗骸最早可以追溯到500万年前左右。根据这些发现，作者提出鳄鱼从澳大拉西亚向西，经非洲迁移到了美洲。

摘要：

Molecular and morphological phylogenies concur in indicating that the African lineages formerly referred to Crocodylus niloticus are the sister taxon the four Neotropical crocodiles (Crocodylus intermedius, C. moreleti, C. acutus and C. rhombifer), implying a transoceanic dispersal from Africa to America. So far the fossil record did not contribute to identify a possible African forerunner of the Neotropical species but, curiously, the oldest remains referred to the African C. niloticus are Quaternary in age, whereas the oldest American fossils of Crocodylusare older, being dated to the early Pliocene, suggesting that another species could be involved. We re-described, also thanks to CT imaging, the only well-preserved topotipic skull of Crocodylus checchiaiMaccagno, 1947 from the late Miocene (Messinian) African site of As Sahabi in Libya. As previously suggested on the basis of late Miocene material from Tanzania, C. checchiai is a valid, diagnosable species. According to our phylogenetic analyses, C. checchiai is related to the Neotropical taxa and could be even located at the base of their radiation, therefore representing the missing link between the African and the American lineages.

（来源：科学网）