Comparative Studies on The Skull Morphology of Chinese Species of Agkistrodon and Deinagkistrodon,With Discussion on Their Classification (Serpentes:Crotalinae)

The classification of some Chinese species of Agkistrodon and Deinagkistrodon remains controversial.As to now,the works mainly dealt with external morphological feathers and little involved internal characters.In this paper,a comparative study on skull morphology of 8 Chinese species (including subspecies) of Agkistrodon and Deinagkistrodon from 13 populations is performed,and the status and validity of some species are discussed.The results reveal:1) brevicaudus is different from its congener blomhoffii in the following characters:the squamosal of blomhoffii doesnt extend beyond the posterior end of the braincase and pterygoid teeth extend beyond the junction with the ectopterygoid.So it supports the suggestion made by Zhao (1998) that brevicaudus,which was treated as a subspecies of blomhoffii by many workers,should be placed at a species status and designated A.brevicaudus.2) ussurisensis is separable from blomhoffii by the presence of weak parietal shield,broad and short lateral process of the fork of the ectopterygoid,pterygoid teeth not extending beyond the junction with ectopterygoid,squamosal extending beyond the posterior end of the braincase;from halys by the presence of postfrontal touches frontal,dorsal scale rows at midbody 21.These characters strengthen the idea that ussuriensis is a full species.3) saxatilis differs from intermedius in several characters,skull proportion of length to width,shape of parietal,the parietal shied and so on,so it is confirmed that saxatilis,which was treated as a subspecies of intermedius by Gloyd et al.(1990),is a full species.4) shedaoensis is distinct from its congener saxatilis in characters of shape of squamosal,basisphenoid and basioccipital process,postfrontal;it is a valid species.5) A.halys qinlingensis Song can be separable from the relative species such as strauchii,halys and intermedius in the following characters:the shape of parietal,pterygoid teeth dont extend beyond the junction with ectopterygoid,squamosal extends beyond the posterior end of the braincase,parietal shield and dorsal scale rows at midbody.Thus raising A.h.qinlingensis as a full species is supported.Comparison studies on skulls among genera Agkistrodon and Deinagkistrodon are also completed.In the end of the paper,the key to these 8 species based on the skull characters was provided.