Department of Ecology, Laboratory of Evolutionary Biology, Faculty of Natural Sciences, Comenius University in Bratislava, 84215, Bratislava, Mlynská dolina, Slovakia.
Département Adaptation du Vivant, UMR 7179C.N.R.S/ Muséum National d'Histoire Naturelle, 55 rue Buffon, 75005, Paris, France.
Sci Rep. 2020 Jan 10;10(1):109. doi: 10.1038/s41598-019-57014-5.
We here present the first detailed study of the specimen KNM-RU 18340 from Rusinga Island (Kenya), the only known complete early Miocene chameleon skull, using micro-CT. This specimen represents one of the oldest chameleon fossils ever recovered. For the first time, the skull bone internal surfaces, their sutures, and elements contained inside the rocky matrix are observed. Our morphological comparisons and phylogenetic analyses place this specimen confidently in the genus Calumma and a new species, Calumma benovskyi sp. nov., is erected for it. Since all species of this genus are endemic to Madagascar, this fossil uniquely demonstrates the existence of Calumma on continental Africa in the past. Our results challenge the long-held view that chameleons originated on Madagascar and dispersed over water to Africa, and provide a strong evidence of an African origin for some Malagasy lineages. The Oligocene-early Miocene dispersal to Madagascar, using oceanic currents that favoured eastward dispersal at that time, is a highly supported scenario matching the suggested dispersal of lemurs to this island. This is consistent with a previously suggested hypothesis based on molecular data.
我们在此首次利用微计算机断层扫描技术对来自肯尼亚鲁辛加岛（Rusinga Island）的 KNM-RU 18340 标本进行了详细研究，该标本是已知的唯一完整的早中新世变色龙头骨。该标本代表了迄今为止发现的最古老的变色龙化石之一。首次观察到了岩石基质内部的头骨骨内表面、它们的缝线和包含的元素。我们的形态比较和系统发育分析将该标本明确归入 Calumma 属，并为其建立了一个新种，Calumma benovskyi sp. nov.。由于该属的所有物种均为马达加斯加特有，因此该化石独一无二地证明了过去在非洲大陆上存在 Calumma。我们的研究结果挑战了变色龙起源于马达加斯加并通过水扩散到非洲的长期观点，并为一些马达加斯加谱系起源于非洲提供了有力证据。在当时有利于向东扩散的洋流的作用下，从中新世到上新世的向马达加斯加的扩散是一个得到高度支持的情景，与向该岛屿扩散的狐猴相匹配。这与基于分子数据的先前假设一致。
