GEOGRAPHICAL VARIATIONS OF SKULL AMONG THEPOPULATIONS OF NEOPHOCAENA IN CHINESE WATERS
GAO Anli ZHOU Kaiya(Department of Biology, Narmal University, Nanjing, 210097)
Geographical variations of skull among the Yangtze,Yellow Sea and South ChinaSea populations of the finless porpoise,Neophocaena phocaenoides,in Chinese waterswere studied using 42 skull measurements based on 144 specimens(40 from Yangtzepopulation,59 from Yellow Sea population and 45 from South China Sea population)deposited in the Cetacean Research Laboratory,Naijing Normal University. The t-testand covariance analysis(Tab.2)demonstrated that:Condylobasal length in the adultsof the Yangtze population was shorter than that of the other two populations(Fig. 1).The South China Sea population had shorter rostrum length(Fig.2a),but it had thelargest width of rostrum,the Yangtze population had the second,and the Yellow Seapopulation had the smallest(Fig,2b).The Yellow Sea population was smaller in thewidth of premaxillaries, zygomatic,preorbital(Fig. 2c)and postorbital.The South 168 China Sea population had more teeth on maxillaries while the Yellow Sea population hadmore teeth on mandibles.Tooth number of the Yangtze population was relatively small-er.The South China Sea population had also larger width of pterygoids(Fig.2d)andinterior nares,but smaller orbital length and preorbital length of lacrimal.The Yangtzepopulation had longer temporal fossa and periotic,wider occipital condyles. The discriminant analysis(Tab.3,Fig.3)showed that:1)Difference in the skullmeasurements among the three Chinese populations was demonstrated even forneonates;2)Difference between the South China Sea population and the other two waslarger than that between the Yangtze and Yellow Sea populations.3)The rostrumlength and rostrum width valued by previous authors were not the optimal group ofskull characters to distinguish the Chinese populations. Generally,the difference in theskull among different geographical populations was represented by a number of vari-ables. Although we have distinguished the populations using a few external measure-ments(reported in another paper),we could not do it using a few skull characters. Itimplies that in the course of population evolution,the osteological adaptation of Neopho-caena took place at a slower rate than the external morphology did.