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History of the Zygoptera 

 palkontoeogy 



The oldest records of insects which resembled Odonata are found 

 in the upper Carboniferous. The wings are the only parts which are 

 well preserved, but these are very different from the wings of living 

 Odonata. The fossil species are termed Protodonata by Handlirsch 

 and are thought to be connected with the still more ancient forms, the 

 Paleodictyoptera, which are the most primitive of all fossil insects. The 

 features which distinguish the Protodonata from the Paleodictyop- 

 tera and link them to the true Odonata include the fusion of the 

 longitudinal veins at the base of the wing; the presence of numerous 

 orderly arranged cross-veins; the appearance of interposed veins or 

 sectors between the longitudinal veins; and, finally, the approxima- 

 tion of the wings themselves at the base. The protodonate wing, 

 however, differs from that of true Odonata in the lack of stigma and 

 nodus and in the supposed absence of that typical feature, the cross- 

 ing of the radial sector over media. It is unfortunate that more of 

 the bodies of these interesting forms have not been preserved, for 

 it would be advantageous to know v/hat types of head, thorax, and 

 abdomen they possessed. 



The next remains of importance are found in the Jurassic Lias of 

 England and are much more closely related to living species than the 

 Protodonata. They are classed as Odonata and divided into two sub- 

 orders, the Anisozygoptera and Archizygoptera. There is a single 

 living representative of the Anisozygoptera in Epiophlebia (Paleo- 

 phlebia) of Japan, but the Archizygoptera have no living represen- 

 tative, and seem to be merely an offshoot from the Protodonata which 

 apparently disappeared after a short stay in geological history. The 

 archizygopterous wings show marked deviations from the original 

 type of the Protodonata, and a very near approach to some of the 

 zygopterous wings of today. The reduction in number of cells and 

 cross-veins is characteristic of both ancient and modern forms, but 

 the absence of the arculus and the separation of media and radius to 

 the very base of the wing, distinguish the fossil species from any 

 living forms. The Anisozygoptera have characters common to both 

 Gomphidae and Agrionidae, the oldest fossils being perhaps more 

 closely related to the Gomphidae. The wings have nodus and stigm.a, 

 and the radial sector plainly crosses the median vein. The degree of 

 obliquity of the cjuadrangle and the presence of many interposed 

 sectors between the longitudinal veins place them with the Agrioni- 

 dae. The head and the wings resemble those of Gomphidae in shape. 



