Oliveira Ivo de Sena, Bai Ming, Jahn Henry, Gross Vladimir, Martin Christine, Hammel Jörg U, Zhang Weiwei, Mayer Georg
Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Box 92, Beichen West Road 1, Chaoyang District, 100101 Beijing, China; Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany.
Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Box 92, Beichen West Road 1, Chaoyang District, 100101 Beijing, China.
Curr Biol. 2016 Oct 10;26(19):2594-2601. doi: 10.1016/j.cub.2016.07.023. Epub 2016 Sep 29.
The anomalous occurrence of supposedly Gondwanan taxa in Laurasian-derived regions remains an intriguing chapter of paleobiogeographical history. Representatives of Peripatidae, a major subgroup of velvet worms (Onychophora), show a disjointed distribution in the neotropics, tropical Africa, and Southeast Asia, the latter being the only landmass previously associated with Laurasia [1, 2]. The arrival of these animals in Southeast Asia is explained by two alternative, albeit not mutually exclusive, hypotheses: an early migration via Europe before continental drift (Eurogondwana hypothesis) or transportation via insular India during the Cretaceous and Paleogene ("out-of-India" hypothesis) [3-6]. The latter hypothesis is based on a single extant species of Peripatidae, Typhloperipatus williamsoni, in India. †Cretoperipatus burmiticus from Myanmar is the oldest fossil onychophoran found in amber [7], dating to sometime between the two proposed scenarios, and hence crucial for clarifying how Gondwanan lineages of these low-vagility animals reached Southeast Asia (see also Supplemental Information). Based on the anatomical reconstruction of †C. burmiticus using synchrotron radiation-based X-ray microtomography (SRμCT) and comparisons with extant taxa, we resolved this fossil species within Onychophora, particularly within Peripatidae, with T. williamsoni as its closest extant relative. This suggests that an early Eurogondwanan migration of peripatids was the most likely event, as Burmese amber is too old to be compatible with the out-of-India hypothesis. Moreover, peripatids probably colonized India only recently from Myanmar, refuting the putative Gondwanan relict status of Indian onychophorans. Finally, preservation artifacts identified in the novel amber material might have a major impact on studies of onychophoran stem and/or crown groups.
在源自劳亚大陆的地区出现本应属于冈瓦纳类群的生物，这一异常现象仍是古生物地理历史中引人入胜的篇章。栉蚕（有爪动物门）的一个主要亚群——栉蚕科的代表物种，在新热带地区、热带非洲和东南亚呈现出间断分布，东南亚是此前唯一与劳亚大陆相关的陆地[1,2]。这些动物抵达东南亚有两种虽非相互排斥但截然不同的假说：一是在大陆漂移之前通过欧洲进行早期迁移（欧洲冈瓦纳假说），二是在白垩纪和古近纪期间通过印度岛屿进行迁移（“走出印度”假说）[3 - 6]。后一种假说基于印度现存的一种栉蚕科物种——威廉森盲栉蚕。来自缅甸的缅甸白垩纪栉蚕是在琥珀中发现的最古老的有爪动物化石[7]，其年代介于上述两种假说所设想的时间之间，因此对于阐明这些低扩散能力的动物的冈瓦纳谱系如何抵达东南亚至关重要（另见补充信息）。基于使用基于同步辐射的X射线显微断层扫描（SRμCT）对缅甸白垩纪栉蚕进行的解剖结构重建，并与现存类群进行比较，我们将这个化石物种归入有爪动物门，特别是栉蚕科，威廉森盲栉蚕是其现存的最亲近的亲属。这表明栉蚕科动物早期通过欧洲冈瓦纳的迁移是最有可能发生的事件，因为缅甸琥珀年代太过久远，与“走出印度”假说不相符。此外，栉蚕科动物可能是最近才从缅甸殖民到印度的，这反驳了印度有爪动物所谓的冈瓦纳残遗地位。最后，在这种新型琥珀材料中发现的保存假象可能会对有爪动物干群和/或冠群的研究产生重大影响。
