以中国科学院古脊椎动物与古人类研究所研究员邓涛为首的研究小组在《美国科学院院刊》(PNAS)上发表论文,对在西藏阿里地区札达盆地上新世地层中发现的三趾马骨架化石进行运动功能分析,从而虚拟再现了其生态环境,并据此推测出青藏高原在460万年前的上新世中期的古海拔高度。4月23日,PNAS的网络版(Early Edition)披露了这一最新研究成果。
关于青藏高原的隆升历史和过程,尤其是不同地质时期的古高度,长久以来都存在激烈争论。邓涛等人通过对札达三趾马骨架化石的研究,证明它是一种生活于高山草原上善于奔跑的三趾马。这样的开阔环境在札达盆地所处的陡峭青藏高原南缘应位于林线之上,根据与现代植被垂直带谱的对比并经古气温校正,札达盆地当时的海拔高度约为4000米,由此证明西藏南部至少在上新世中期已经达到现在的高度。
在青藏高原发现的三趾马化石曾经为研究高原的隆升历史提供了坚实的证据,其中就包括在札达发现并被命名为札达三趾马的头骨和下颌骨。新的三趾马骨架化石的牙齿特征指示其属于札达三趾马,古地磁测年结果显示其埋藏的地层形成于460万年前。由于骨骼化石的形态和附着痕迹能够反映肌肉和韧带的状态,所以可以据此分析绝灭动物在其生活时的运动方式。札达三趾马的骨架保存了全部肢骨、骨盆和部分脊椎,因此提供了重建其运动功能的机会。
札达三趾马生活的460万年前对全球来说正处于上新世中期的温暖气候中,温度比现代高约2.5℃。按照100米0.6℃的气温直减率,则札达马生活时期札达地区的林线高度应位于海拔4000米处。札达三趾马骨架化石的发现地点海拔接近4000米,也就是说,札达盆地至少在上新世中期就已经达到其现在的海拔高度。(生物谷:Bioon.com)
doi:10.1073/pnas.1201052109
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Locomotive implication of a Pliocene three-toed horse skeleton from Tibet and its paleo-altimetry significance
Tao Deng, Qiang Li, Zhijie Jack Tseng, Gary T. Takeuchi, Yang Wang, Guangpu Xie, Shiqi Wang, Sukuan Hou, and Xiaoming Wang
Three benchtop high-throughput sequencing instruments are now available. The 454 GS Junior (Roche), MiSeq (Illumina) and Ion Torrent PGM (Life Technologies) are laser-printer sized and offer modest set-up and running costs. Each instrument can generate data required for a draft bacterial genome sequence in days, making them attractive for identifying and characterizing pathogens in the clinical setting. We compared the performance of these instruments by sequencing an isolate of Escherichia coli O104:H4, which caused an outbreak of food poisoning in Germany in 2011. The MiSeq had the highest throughput per run (1.6 Gb/run, 60 Mb/h) and lowest error rates. The 454 GS Junior generated the longest reads (up to 600 bases) and most contiguous assemblies but had the lowest throughput (70 Mb/run, 9 Mb/h). Run in 100-bp mode, the Ion Torrent PGM had the highest throughput (80–100 Mb/h). Unlike the MiSeq, the Ion Torrent PGM and 454 GS Junior both produced homopolymer-associated indel errors (1.5 and 0.38 errors per 100 bases, respectively).