扬子鳄的起源

The Origin of The Chinese Alligator( Alligator sinensis )

介绍了现存鳄彼此间的亲缘关系、扬子鳄起源的时间和地点。主要结论可归纳如下 :①现存鳄类在科、属、种分类上都存在不同意见 ;②扬子鳄与密河鳄被分在同一属内 ,但两者之间的亲缘关系存在争议 ,两者在形态、生化、细胞、分子生物学上差异很大 ;③Stell认为扬子鳄在中新世开始出现 ,作者认为它可能起源于渐新世或中新世早期 ;④Stell认为分布于北美的汤氏鳄 (A .thomsoni)可能是扬子鳄的祖先类型 。

This paper deals with the systematic relationships among living crocodiles and the time and place of origin of the Chinese alligator( Alligator sinensis ).The main results may be summarized as follows:1. There is considerable debate on the classification of living crocodiles at all taxonomic levels,i.e. family, genus and species. 2.The Chinese alligator and American alligator( Alligator mississippiensis )are grouped in same genus,but the relationship between them is also a matter of debate. Some morphological, biochemical, cytogenetic and molecular data show these species to be more distinct than the currently accepted classification suggests. 3. Stell(1973)held that the Chinese alligator first appeared during the Miocene.The present author suggests that the Chinese alligator may have originated in the Oligocene or early Miocene. 4. Stell(1973) held that Alligator thomsoni which occurred in North America, may have been antecedent to an unknown species which spread into Asia that became the progenitor of the Chinese alligator, but some authors suggest that the Chinese alligator may have originated in Asia.