保存在印度的年龄为5000万年的琥珀中的昆虫可能提供证据表明该地区的生物群并非像目前认为的那样孤立进化。印度的独特的动植物群被认为在印度大陆1亿年的向北运动中进化了出来，这种向北运动以形成了喜马拉雅山脉的大碰撞而终结。
Jes Rust及其同事从印度西部5000万年前的沉积物中提取了超过300磅琥珀，并发现了一种独特的化学特征，它提示这种树脂是由全球广泛分布的一类热带树产生的。这组科学家用溶剂溶解了这种琥珀，并获取了完整保存的来自超过55科的古代昆虫、蜘蛛纲动物和甲壳纲动物的700多种标本以及丰富的植物和真菌残骸。这些昆虫显示出了与来自亚洲和澳大利亚的当代物种以及最远见于墨西哥和中美洲的古代祖先的出人意料的地理联系。
这组作者说，该研究提供了直接的化石证据，证明了印度琥珀含有具有多样的动物群的热带森林的早期记录，并证明了碰撞前的印度可能并非像人们认为的那样在生物学上是孤立的。（生物谷Bioon.com）
生物谷推荐英文摘要：
PNAS doi: 10.1073/pnas.1007407107
Biogeographic and evolutionary implications of a diverse paleobiota in amber from the early Eocene of India
Jes Rusta,1, Hukam Singhb, Rajendra S. Ranac, Tom McCanna, Lacham Singhc, Ken Andersond, Nivedita Sarkare, Paul C. Nascimbenef, Frauke Stebnera, Jennifer C. Thomasg, Monica Solórzano Kraemera,h, Christopher J. Williamsi, Michael S. Engelg, Ashok Sahnie,j, and David Grimaldif,1
aSteinmann Institute, University of Bonn, 53115 Bonn, Germany;
bBirbal Sahni Institute of Palaeobotany, Lucknow 226007, India;
cDepartment of Geology; Hemwati Nandan Bahuguna Garhwal University, Srinagar 246174, India;
dDepartment of Earth Sciences, Southern Illinois University, Carbondale, IL 62901;
eCentre for Advanced Study in Geology, University of Lucknow, Lucknow 226007, India;
fAmerican Museum of Natural History, New York, NY 10024-5192;
gDivision of Entomology, Natural History Museum, and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66049-2811;
hSenckenberg Research Institute and Museum, 60325 Frankfurt, Germany;
iDepartment of Earth and Environment, Franklin and Marshall College, Lancaster, PA 17603; and
jCentre of Advanced Study in Geology, Panjab University, Chandigarh 160022, India
For nearly 100 million years, the India subcontinent drifted from Gondwana until its collision with Asia some 50 Ma, during which time the landmass presumably evolved a highly endemic biota. Recent excavations of rich outcrops of 50–52-million-year-old amber with diverse inclusions from the Cambay Shale of Gujarat, western India address this issue. Cambay amber occurs in lignitic and muddy sediments concentrated by near-shore chenier systems; its chemistry and the anatomy of associated fossil wood indicates a definitive source of Dipterocarpaceae. The amber is very partially polymerized and readily dissolves in organic solvents, thus allowing extraction of whole insects whose cuticle retains microscopic fidelity. Fourteen orders and more than 55 families and 100 species of arthropod inclusions have been discovered thus far, which have affinities to taxa from the Eocene of northern Europe, to the Recent of Australasia, and the Miocene to Recent of tropical America. Thus, India just prior to or immediately following contact shows little biological insularity. A significant diversity of eusocial insects are fossilized, including corbiculate bees, rhinotermitid termites, and modern subfamilies of ants (Formicidae), groups that apparently radiated during the contemporaneous Early Eocene Climatic Optimum or just prior to it during the Paleocene-Eocene Thermal Maximum. Cambay amber preserves a uniquely diverse and early biota of a modern-type of broad-leaf tropical forest, revealing 50 Ma of stasis and change in biological communities of the dipterocarp primary forests that dominate southeastern Asia today.
