长吻鳄科(爬行纲:鳄目)系统发育研究进展及展望

A review and prospect about systematics and phylogeny of Gavialidae(Reptilia:Crocodilia)

在鳄类系统发育研究中,长吻鳄科Gavialidae的系统发育位置存在较大分歧。根据分子生物学数据,恒河鳄Gavialis gangeticus和长吻马来鳄Tomistoma schlegelii是姐妹群,它们共同构成长吻鳄科;短吻鳄科Alligatoridae占据整个鳄类系统发育的基干部位。根据形态学数据,恒河鳄是其他所有鳄类的外类群。当对分子生物学数据和形态学数据进行综合分析时,其结果强烈支持分子假说。文章从恒河鳄系统发育位置出发,探讨恒河鳄与长吻马来鳄谱系发育位置在分子生物学与形态学数据上的冲突;提出鳄类谱系发育的分子生物学与形态学数据冲突的解决有赖于亚洲东部过渡型长吻鳄科化石的发现,这些过渡类型的化石在重建鳄类谱系发育和探讨长吻鳄亚科的形态返祖之谜等方面具有重要意义。

There is a long history in studying crocodylians,but the phylogeny of crocodylians in general,and phylogenetic relationships of gavialids in particular,are highly controversial.Molecular evidence suggests that Gavialis gangeticus and Tomistoma schlegelii,the only two living gavialids,are sister taxa.Alligatoridae occupies the root of the phylogenetic tree of crocodylians.Morphological data instead indicate that Gavialis gangeticus is the outgroup of all other crocodylians.When the molecular and morphological data are combined together,the results strongly support the molecular hypothesis.Here we focus on discussing the conflicts regarding the phylogenetic positions of Gavialis gangeticus and Tomistoma schlegelii by reviewing different lines of evidence from molecular and morphological data.Based on the results of previous studies,we propose that the molecular-morphological conflict of crocodylian phylogeny could be resolved with the discovery of new intermediate fossil gavialids in eastern Asia.These intermediate fossils will play key roles in reconstructing a stable phylogeny of Crocodilia and discussing the morphological atavism of gavialines.