論文標題：Fossil lemurs from Egypt and Kenya suggest an African origin for Madagascar’s aye-aye
作者：Erik R. Seiffert et al
數字識別碼：10.1038/s41467-018-05648-w
《自然-通訊》近日發表的一項研究Fossil lemurs from Egypt and Kenya suggest an African origin for Madagascar’s aye-aye稱，曾被廣泛認為是一種果蝠的化石種Propotto leakeyi，其實是指猴型下目的一種狐猴，是馬達加斯加指猴的近親。在這項重新評估的基礎上，系統發育分析結果顯示，有兩個狐猴支系獨立地從非洲遷徙到了馬達加斯加，這一結果挑戰了當前公認的觀點——狐猴進入馬達加斯加的過程只發生了一次。
圖1：馬達加斯加指猴。David Haring
1967年，肯尼亞中新世早期（約2300萬-1600萬年前）沉積地層中發現的三個下頜斷塊被歸入一種名為Propotto leakeyi的新靈長動物。不過，這種解釋很快就受到了駁斥，有人指出Propotto leakeyi並不是靈長動物，而是一種果蝠——半個多世紀以來，後一種觀點尚無人提出質疑。
圖2：馬達加斯加指猴。David Haring
美國南加州大學的Erik Seiffert和同事在分析評估了Propotto leakeyi的牙齒，以及埃及發現的距今約3400萬年的靈長動物Plesiopithecus teras（一種近猿）的化石後發現：Propotto leakeyi不僅是靈長動物，還是Plesiopithecus teras和指猴的近親。研究結果顯示，狐猴型下目和指猴型下目的共同祖先擁有非洲血統，而且這兩個狐猴支系曾沿不同路徑橫跨莫桑比克海峽，最終抵達馬達加斯加。
圖3：Propotto、Plesiopithecus和指猴的下頜臼齒形態比較，以及Plesiopithecus和Propotto放大的前牙。Gunnell et al.
作者指出他們的分析主要基於牙齒形態學，因此，只有在更新、更完整的化石發現後，才能對這些假說作進一步檢驗。
摘要：In 1967 G.G. Simpson described three partial mandibles from early Miocene deposits in Kenya that he interpreted as belonging to a new strepsirrhine primate, Propotto. This interpretation was quickly challenged, with the assertion that Propotto was not a primate, but rather a pteropodid fruit bat. The latter interpretation has not been questioned for almost half a century. Here we re-evaluate the affinities of Propotto, drawing upon diverse lines of evidence to establish that this strange mammal is a strepsirrhine primate as originally suggested by Simpson. Moreover, our phylogenetic analyses support the recognition of Propotto, together with late Eocene Plesiopithecus from Egypt, as African stem chiromyiform lemurs that are exclusively related to the extant aye-aye (Daubentonia) from Madagascar. Our results challenge the long-held view that all lemurs are descended from a single ancient colonization of Madagascar, and present an intriguing alternative scenario in which two lemur lineages dispersed from Africa to Madagascar independently, possibly during the later Cenozoic.
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